exä|xã Éy _|àxÜtàâÜxexä|xã Éy _|àxÜtàâÜxexä|xã Éy _|àxÜtàâÜxexä|xã Éy _|àxÜtàâÜx

REVIEW OF LITERATURE

Biological control may be defined as ‘A reduction of pathogens through the action

of other living organisms which occur naturally or through the manipulation of the

environment’. The term was introduced in scientific literature by G.F. Von Tabuef in 1914

(Baker, 1987). Interest in biological control first observed in 1920s and 1930s, when some

plant pathogens were suppressed by microbes producing some antibiotics. A turning point

for research on biological control of plant pathogens came after a gap of more than 30 years

when in 1963, an International Symposium, on ‘Ecology of soil-borne plant pathogens

prelude to biological control’ was held in Berkeley, USA.

Before attaining the true management of soil microbes, it is essential to understand

better the interaction between plants and microbes in the soil around the roots. Management

of soil-microbes is necessary to optimize N and P nutrition of plants. There are extensive

microbial activities in rhizosphere soil which is colonized by a wide range of microbes with

important effects on plant nutrition, growth and health. Among these micro-organisms the

importance of mycorrhiza deserve special attention.

Mycorrhizal fungi have been involved in the adaptation of plants to unfavourable

conditions from the very beginning (Penninsi, 2004). The most prominent effect of this

group of fungi is improved phosphorus nutrition of the host plant in soil (Koide, 1991).

However uptake of nitrogen, zinc, copper and other micro-nutrients enhanced as well. The

ability of AM fungi to suppress root diseases caused by soil borne pathogens have been

intensively studied in the last thirty years. Numerous reviews on the efficacy of AM fungi

as biological control agents have been published by Schenk and Kellam, (1978);

Schoenbeck, (1979); and Siddiqui and Mahmood, (1995).

The main objective of this review is to analyze the role of bioinoculants on

biological control of plant diseases caused by plant-parasitic nematodes especially by root-

knot nematode M. incognita. However, the informations regarding the interaction of these

organisms with nematodes are meager and lacking in Indian context. It is therefore need to

describe the research findings by various workers.

Distribution, Identification and Classification of AM fungi

Mycorrhizal fungi are a major component of agricultural natural resources and

members of kingdom fungi. The term ‘mycorrhiza’ is derived from Greek word which

means ‘fungus root’ (Friberg, 2001). The term was first coined by A.B Frank a German

plant pathologist in 1855 to describe the symbiotic relationship between plant roots and

fungi. AM associations have been observed in 1000 genera of plants belonging to 200

families. There are about 300,000 receptive hosts in world flora (Kendrick and Berch,

1985). Over 90% of plant species are associated with mycorrhizal fungi of vascular and

non-vascular in nature. Some important crops such as carrot, maize, soybean, citrus fruits,

tomatoes and pepper harbouring the population of AM fungi (Muchovej, 2004).

The abundance and distribution of AM fungi have been studied by many workers

(Anderson et al., 1984; Hussain et al., 1995). AM fungi are reported to be found in diverse

land areas such as calcareous grasslands, arid/semi-arid grasslands, several temperate

forests, tropical rainforests and shrubs lands in diverse part of the world (Muthukumar and

Udaiyan, 2002; Renker et al., 2005). Reyes and Ferrera (1992) observed that AM

colonization levels are higher in herbs than in shrubs. They have also been reported in

floating (Bagyaraj et al., 1979) and submerged aquatic plants (Clayton and Bagyaraj, 1984).

They are found in Gymnosperms (Harley, 1969), Pteridophytes (Cooper, 1976) and

Bryophytes (Smith and Read, 1997). Recently AM fungi have received more attention

especially in African countries such as Namibia, Morocco, Nigeria, Zambia and South

Africa.

According to Mosse and Bowen (1968), AM population is more in cultivated soil as

compared to virgin soil. AM fungi are mostly found in top 15-30 cm of soil and their

number decreases markedly below the top 15 cm of soil (Redhead, 1977). Moisture content

had negative influence on AM development. Significant correlation between AM fungi, soil

pH, moisture and P content has been observed by Rani and Manoharachary, (1994); and

Bharadwaj et al., (1997).

The pattern of distribution is also very important phenomena in the land growing

crops. Using relative simple technique of wet sieving and decanting (Gerdemann and

Nicolson, 1963), spores have been isolated from soils. The available reports indicate that

there is a more or less uniform distribution of all the genera in both the hemispheres.

Mycorrhiza are classified on the basis of morphological characteristics, biochemical

and molecular properties of soil-borne resting spores (Morton and Benny, 1990; Mukerji et

al., 2002; Peterson et al., 2004). Arbuscular mycorrhiza were formerly classified in the

phylum zygomycota under the family Endogonaceae, but this was later re-evaluated when

AM fungi produced asexual spores rather than sexual spores like other endogone species

(Pawlowska and Taylor, 2004). Seven different types of mycorrhizal associations have been

recognized, viz., Ecto-and Endo mycorrhiza, Ericoid mycorrhiza, orchidaceous mycorrhiza,

Arbutoid mycorrhiza, Monotropoid mycorrhiza and Ectendo mycorrhiza (Smith and Read,

2008). Among these groups, endo-mycorrhiza represent a group of fungi which are

geographically ubiquitous and occur over a wide ecological range.

On the basis of the advance techniques, the latest classification of AM fungi

belonging to the class Glomeromycetes of the phylum Glomeromycota (Schubler et al.,

2001; Walker et al., 2007) and the genus Glomus is said to be the largest within the

glomales. AM fungi played diverge role in the Indian Agricultural System for various ways.

Role of AM fungi in nutrient uptake

AM fungi involved in the symbiotic activities with the roots of different plants.

Interests in AM fungal symbiosis observed in agriculture, forestry, rehabilitation and in

environments (Cuenca et al., 1998; Friberg, 2001). The major benefits of AM fungi include

enhanced nutrient uptake, increased tolerance to root pathogens, drought resistance,

tolerance to toxic heavy metals and improved soil aggregation and structure. The main

hurdle in exploiting beneficial effects of AM fungi for improved agricultural productivity is

the obligate nature of the symbiont. They can not be grown and cultured in the absence of

their host plants. The greatest impediment to AMF commercialization is the obligate

biotrophicity of the fungi, which necessitates the use of a living host for sustained survival

and propagation. The cost of inoculum production can be relatively high as compared to

other organisms. Furthermore, the lack of consistency in efficaceous product and poor

market demands has contributed to the insignificant and slow progress in this area.

AM fungi have been reported to function as biofertilizers, biostimulators,

bioprotectors etc. and therefore can benefit the area of agriculture, horticulture and

sylviculture immensely (Kendrick and Berch, 1985). AM fungi received wide attention as

part of an increasing popular paradigm that considers as an active and diverse soil biological

community as essential for increasing the sustainability of agriculture system (Gianinazzi

and Schuepp, 1994). It has been established that AM fungi have the ability to sequester

mineral nutrients and transfer to the plant roots when nutrients are in high concentration in

the soil. Macro-and micronutrients are required by the plants in varying amounts.

In the majority of mycorrhizal type improvements in plant growth followed by root

colonization by AM fungi occur as a result of acquisition of the mineral nutrient (especially

P) from the soil (George, 2000). AM fungi are known to enhance uptake of the

macronutrients like phosphorus from the soil. AM fungi help the plants in two ways: firstly

they help in the uptake of these elements which are considered to be relatively immobile

and secondly they take up these elements and store them so as to prevent their

concentrations to reach toxic levels (Gonzalez-Chavez et al., 2002; Pawlowska and Charvat,

2004).

Phosphorus deficiency is one of the most widespread mineral nutrient stresses

limiting crop production in the world (Sanchez and Salinas, 1981; Holford, 1997).

Phosphorus is the essential nutrient required for the plant growth and is found in many soils

in organic and complex inorganic forms. Due to its slow solubility and mobility, plants can

not readily utilize P in an organic or complex inorganic form (Schachtman et al., 1998).

Inorganic phosphate present in soluble forms in the soil can be readily utilized by plants but

in limited amounts. The enzyme phosphatase produced by AM fungal extraradical hyphae

hydrolyses and releases P from organic complexes and facilitates the absorption of P and

other nutrients thereby creating a depletion zone around the roots (Li et al., 1991; Jackobson

et al., 1992). These depletion zones give mycorrhizal plants a great advantage because of

the ability of ERH to extend past this nutrient depletion zone to enhance absorption (Sylvia

et al., 2001). Thus AM fungi intervene to enhance nutrient uptake through the spread of

extraradical hyphae into the surrounding soil and hydrolyzing an unavailable sources of P

with the aid of secreted enzymes such as phosphatase (Koide and Kabir, 2000).

Enhancement of phosphorus uptake by AM fungi and transfer to the host plant has been

reported by several workers (Karandashov and Bucher, 2005; Cardoso et al., 2006).

Sylvia et al. (2001) evaluated the influence of arbuscular mycorrhizal fungi and

concluded that the role of mycorrhiza in plant competition for nutrients is markedly

impacted by soil nutrient status and reduced P application in tomato plants.

Mamtha and Bagyaraj (2002) studied the effect of different levels of VAM

application on growth and nutrition of tomato under greenhouse conditions. The different

levels of Glomus fasciculatum improved the plant growth, biomass, P content and

mycorrhizal root colonization. Chaoxing et al. (2006) studied the effects of different AM

fungi strains on tomato growth and nutrient absorption during seedling stage. They found

inoculated plants produced higher dry matter and showed higher nutrient uptake than

uninoculated ones. Glomus mosseae strains showed higher infection rate than the others.

Role of AM fungi in nematode control

Plant-parasitic nematodes are among the most widespread and important pathogens

causing crop losses across the world. Plant-parasitic nematodes and mycorrhizal fungi are

commonly found inhabiting the same niche and colonizing roots of their host plants. These

two groups of micro-organisms exert a characteristic but opposite effects on plant health.

The potential role of mycorrhizal fungi for the control of nematode diseases has received

considerable attentions (Osman et al., 1990; Santhi and Sundarbabu, 1995; Price et al.,

1995). AM fungi have shown an antagonistic influence on the population of plant-parasitic

nematodes (Bagyaraj et al., 1979; Sivaprasad et al., 1990; Osman et al., 2005).

Jain and Hasan (1986) reported that nematodes did not affect VAM sporulation

adversely when there was 50 percent root colonization. The nematodes number was lower

and rarely infect VAM colonized region of the roots. Increased spore production and higher

root colonization by VAM fungi in the presence of nematodes have also been observed by

Ingham, (1988). Nematode susceptible plants colonized by AM fungi were better able to

tolerate plant-pathogenic nematodes (Kellam and Schenck, 1980; Sankaranaryanan and

Sundarababu, 1994).

Sikora (1978) suggested that attractiveness of the root system to M. incognita larvae

was altered by the presence of G. mosseae. As a result of interaction in general, the severity

of nematode diseases was reduced in mycorrhizal plants. The antagonistic effects of AM

fungi on nematodes may be either physical or physiological in nature. Sitaramaiah and

Sikora (1980) observed that Glomus mosseae increased the resistance of tomato plants to

Rotylenchulus reniformis infection. AM fungi can alter the physiology of the roots

including root exudates which were responsible for chemotactic attraction of nematodes.

Sitaramaiah and Sikora (1982) expressed the other version of increasing resistance

in tomato plants colonized by Glomus fasciculatum against Rotylenchulus reniformis by

delaying the nematode attacks in roots. Glomus fasciculatum adversely affect the R.

reniformis during several phases of its life cycle.

Jain and Sethi (1989) showed that the occurrence of Heterodera cajani and VAM

fungi, Glomus fasciculatum and G. epigaeus in Vigna unguiculata were largely independent

of each other and the organisms modify the effect of each other to some extent. The

presence of G. fasciculatum showed a adverse effects on cyst production and multiplication

of nematodes while G. epigaeus exhibited a different trends.

Heald et al. (1989) have suggested increased nutrient uptake by mycorrhizal fungi

enhances plant tolerance relative to detrimental effects on nematodes. Similarly it had been

found that the presence of mycorrhiza increased the tolerance of plants to diseases (Chandra

and Kehri, 1996). Sivaprasad et al. (1990) observed that the pre-inoculation of Piper nigrum

cv. Panniyur cuttings with Glomus fasciculatum or G. etunicatum reduced the root-knot by

32.4 and 36.0 per cent respectively and reduced nematode population in roots and

surrounding soils, which significantly increased growth even in the presence of nematodes.

The tolerance of Kiwi plants to M. javanica was increased in presence of G. etunicatum

(Verdejo et al., 1990).

In the similar study, Singh et al. (1990) observed that preinoculation of tomato cv.

Pusa Ruby roots with Glomus fasciculatum resulted in an increase in lignin and phenols and

this might be improved the resistance in tomato plants against root-knot nematode,

Meloidogyne incognita.

Mishra (1996) studied the interrelationship of M. incognita, G. fasciculatum and the

three commonly used herbicides. Higher levels of VAM after 60 days of inoculation

improved growth of tomato plants while simultaneous inoculation of VAM and nematodes

resulted maximum colonization of VAM. Pre-establishment of G. fasciculatum increased

plant growth, decreased the size and number of galls and improved NPK uptake compared

to those plants inoculated with the nematode alone or pre-inoculated with the nematodes to

VAM. Sundarababu et al. (1996) observed that when Glomus fasciculatum was inoculated

15 days prior to nematode inoculation that resulted an enhancing the growth of tomato cv.

CO3 and suppress M. incognita multiplication. Simultaneous inoculation however followed

the similar pattern. G. fasciculatum was unable to suppress nematode growth when the

nematode was inoculated 15 days prior to fungus. Mishra and Shukla (1997) reported that

simultaneous inoculation of G. fasciculatum with M. incognita caused greater reduction in

the number and size of the root-galls induced by nematodes.

Cofcewicz et al. (2001) studied the interaction of arbuscular mycorrhizal fungi

Glomus etunicatum and Gigaspora margarita with root-knot nematode Meloidogyne

javanica and their effects on the growth and mineral nutrition of tomato. They pointed out

that the shoot dry matter and yields were reduced by nematode infection and this was less

pronounced in plants colonized with G. etunicatum than those plant colonized with G.

margarita and non-mycorrhizal plants. The higher tolerance of plants colonized with G.

etunicatum to M. javanica appeared to be associated with P nutrition. Similarly, Labeena et

al. (2002) evaluated the ability of five arbuscular mycorrhiza, viz. G. fasciculatum, G.

macrocarpum, G. margarita, Acaulospora laevis and Sclerocystic dussi to mitigate the

damage caused by M. incognita on tomato cv. Pusa Ruby. They found that G. fasciculatum

was the most efficient in promoting plant growth despite in the presence of nematodes. The

developmental stages of nematode in the roots and density in soil were suppressed by the

AM fungi and the most pronounced effect was exhibited by G. fasciculatum.

Osman et al. (2005) observed the interaction of root-knot nematode and VAM fungi

on common bean plants (Phaseolus vulgaris L.) in the greenhouse. They concluded that the

inoculation with VAM fungus caused a significant increase in plant height and fresh weight

as compared to un-treated plants. The inoculation with VAM fungus caused a significant

increase in phosphorus content. Although there were significant decrease in nematode final

population and gall-index when plants inoculated with nematodes at 15 and 30 day after

mycorrhizal infection.

Castillo et al. (2006) studied the effect of single and combined inoculations of olive

planting stocks cvs. Arbequina and Picual with the arbuscular mycorrhizal fungi Glomus

intraradices, Glomus mosseae or Glomus viscosum and the root-knot nematodes M.

incognita and M. javanica on plant performance and nematode infection. They observed

that prior inoculation of olive plants with AM fungus improved the health status and vigour

of Arbequina and Picual planting stocks during nursery propagation. Indigenous isolates of

AM fungus Glomus fasciculatum were found effective in the management of root-knot

nematode Meloidogyne incognita on tomato (Kantharaju et al., 2005). Shreenivasa et al.

(2007) found that presence of AM fungus (Glomus fasciculatum) reduced penetration of

Meloidogyne incognita larvae in tomato roots. Neog et al. (2007) studied different spore

inoculum levels and time of inoculations of VAM fungus Glomus fasciculatum, and noticed

that inoculation of VAM with two levels, viz., 150 and 300 spores level prior to nematode

inoculation was more effective in reducing number of galls, egg-masses and final nematode

population in soil and increasing plant-growth parameters as compared to simultaneous

inoculation of both VAM and nematode or inoculation of nematode 10 days prior to

inoculation of VAM and the highest reduction was recorded when 300 spores were added 1

days prior to inoculation of nematodes.

AM fungi have the ability to induce systemic resistance against plant- parasitic

nematodes in a root system (Elsen et al., 2008). Anjos et al. (2010) demonstrated that the

establishment of an AM fungus before nematode infection effectively reduced reproduction

of the root-knot nematode Meloidogyne incognita and reduced disease severity in infested

soil seems to be due to physiological alteration in favour of growth of AM fungus.

Aparajita et al. (2009) studied the effect of soil types on efficacy of Glomus

fasciculatum in the management of Meloidogyne incognita on green gram. Nematode

reproduction was found to be minimum in sandy loam soil as compared to other types of

soil when VAM was inoculated simultaneously with nematodes. The plant growth was

found increased when soil was supplemented with VAM fungus. VAM spore population in

soil and mycorrhizal colonization in roots were found higher in coarse textured soil as

compared to clay soil.

Pandey (2011) tested two species of VAM fungi, viz. Glomus mosseae and Glomus

fasciculatum against Heterodera cajani population infecting cowpea. In the first set of

experiment, mixed inoculation of VAM was found more effective in managing H. cajani

population whereas single VAM inoculation Glomus fasciculatum proved to be more

beneficial. In second set of experiment degree of mitigative effects of VAM on Heterodera

cajani depended at the time of VAM and nematodes inoculation. Two weeks prior

inoculation of G. fasciculatum resulted greater reduction in nematode multiplication.

Alguacil et al. (2011) found whether galls produced by M. incognita infection in

Prunus persica roots were colonized by AM fungi or not. Their study finally indicated that

the galls produced in P. persica roots due to infection with M. incognita were found

colonized extensively by a community of AM fungus. They hypothesized that they act as

protection agents against opportunistic pathogens.

Role of Azotobacter in improvement of plant growth and disease development

Azotobacter belongs to family Azotobacteriaceae, aerobic, free living bacteria in

nature. The first representative of the genus, A. chroococcum was discovered and described

in 1901 by the Dutch microbiologist and botanist Martinois Beijerinck. Azotobacter are

gram negative bacteria and found in neutral and alkaline soil (Martyniuk and Martyniuk,

2003), in water (Tejera, 2005) and in association with some plants (Kumar et al., 2007).

The isolated culture of Azotobacter fixes about 10 mg Nitrogen-1 carbon source under in

vitro conditions. They are known to synthesize biological active growth promoting

substances such as Vitamins of B group, IAA and gibberellins. The occurrence of this

organism has been reported from the rhizosphere of a number of crop plants such as rice,

maize, sugarcane, bajra, vegetables and plantation crops (Arun, 2007). Azotobacter

normally fix molecular nitrogen from the atmosphere without symbiotic relationship with

plants, although some species are associated with plants (Kass, 1971).

The incorporation of such kind of biofertilizers play major role in improving soil

fertility, yield attributing characters and thereby final yield have been reported by many

workers (Kachroo and Razdan, 2006; Son et al., 2007). In addition to their application in

soil which minimizes the sole use of chemical fertilizers (Subashini et al., 2007) and save

much money to be spent on such fertilizers. Very little informations are available regarding

the research of Azotobacter and its incorporation in the soil for the exploitations of

beneficial capabilities in the agricultural system.

Jackson et al. (1964) found accelerated growth of tomato stem with inoculation of

Azotobacter. Mishutin (1966) demonstrated that bacterial fertilizers significantly improved

the yield of a wide range of crop plants, specially vegetables. Dumal (1992) reported the

effects of Azotobacter on germination, growth and yield of some vegetables. Martinez et al.

(1993) reported that inoculation of Azotobacter increased tomato seed germination by 33-

46 per cent. Similarly, Gerardo Rosales (2002) reported that soil inoculation with

Azotobacter increased tomato seed germination by 33-46 per cent. Azotobacter

chroococcum have the capability for contributing nitrogen to a number of non-legumes by

trapping the nitrogen from aerial nitrogen reservoir (Singh and Sinsinwar, 2006) and can

meet upto 15-20 kg N per ha requirement of crop besides producing some growth

promoting substances that help in increasing the yield (Das et al., 2006).Various research

workers used Azotobacter chroococcum as a bioinoculants in different crops such as wheat

(Kumar et al., 2001), and herbal crops like Withania somnifera (Kumar et al., 2009) for

requirement of nutrient supply.

Effect of interaction of Azotobacter with other bioinoculants

The interaction between rhizospheric microbes and plants have a great influence on

plant health and soil quality (Lynch, 1990). Among these beneficial rhizospheric microbes,

arbuscular mycorrhizal fungi and plant growth promoting rhizobcteria can be considered

and emphasized in recent years in Indian Agricultural System. Since they inhabited the

common habitats, i.e. the root surface and common functions. They have to interact during

their processes of root colonization as root associated microorganisms. Soil

microorganisms, particularly PGPR, can influence spore formation of AM fungi and

functions. While on the other hand the mycorrhiza can also affect PGPR populations on the

rhizosphere population (Barea, 2000).

Bioinoculants like Azotobacter and others have shown synergistic effect on plant

growth parameters and nutrient uptake of different crops. Seed inoculation with a

combinations of beneficial microorganisms including rhizobia, PGPR and PSB have been

shown to increase crop growth and productivity (Zaidi et al., 2003; Rudresh et al., 2005).

Bagyaraj and Menge (1978) studied the interaction between free living N2-fixing

bacterium Azotobacter chroococcum and mycorrhizal fungus Glomus fasciculatum and

found a synergistic effect on plant growth of tomato. Mycorrhizal infection increased the

population of A. chroococcum in rhizosphere and consequently A. chroococcum enhanced

spore production by the mycorrhizal fungus. Javaid et al. (2000) noticed the response of

crop growth when Vigna radiata (L.) Wilczek was grown in farmyard manure and Trifolium

green amended soils with different isolates of VAM fungus and found a positive results in

both the types of soils. El-Zeiny et al. (2001) observed that inoculation of tomato seedling

with Azotobacter, Azospirillum and Bacillus increased plant height, leaf number per plant,

fruit mean weight and yield as compared to untreated control. Suresh and Bagyaraj (2002)

reported synergistic interaction between AM fungi and asymbiotic N2-fixing bacteria such

as Azotobacter chroococcum, Azospirillum spp. and Acetobacter diazotrophicus.

Synergistic effects of combined inoculations of PGPRs have also been reported in various

crops like potato (Kundu and Gaur, 1980), rice (Tiwari et al., 1989) and sugarbeet and

barley (Cakmakci et al., 1999). Similarly, the synergistic effect of AM fungi and

rhizobacteria such as Azospirillum, Azotobacter, Pseudomonas and Phosphate-solubilizing

bacteria were studied by many workers (Bagyaraj, 1990; Siddiqui, 2003).

Similarly Widada et al. (2003) conducted an experiment to evaluate the interaction

effects of AM fungi or/and rhizobacteria, Phosphate-solubilizing bacteria, (PSB), N2-fixing

bacteria (NFB) and Siderophore producing bacteria (SPB) on the growth and nutrient

uptake of sorghum (Sorghum bicolor). Dual inoculation of AM fungi and rhizobacterium

yielded higher plant dry weight and nutrients uptake compared to the individual

inoculation. The rhizobacteria also increased to help the plant colonization by AM fungi.

These results revealed that the interaction of AM fungi and the selected rhizobacteria has a

potentiality to be developed as biofertilizers.

Bhowmik and Singh (2004) evaluated the efficiency of PGPR like Azospirillum sp.,

Azotobacter chroococcum, Pseudomonas fluorescens, Pseudomonas striata and yeast for

maximization effects of Glomus mosseae in Chloris gayana Kunth. Results revealed that

PGPR considerably enhanced mycorrhizal colonization when compared to yeast. They not

only stimulated AM development but also accelerated the root growth possibly to increase

the surface area for colonization. Similarly, Bashan et al. (2004) reported that inoculation of

Azospirillum significantly increased the plant biomass, nutrient uptake, N content, plant

height, leaf size and root length of cereals. Significant increase in plant height, leaf area was

also observed in different crops when jointly inoculated with Pseudomonas, Azospirillum

and Azotobacter strains (Shaukat et al., 2006b).

Wu et al. (2005) conducted greenhouse experiment to evaluate the effects of four

biofertilizers containing Glomus mosseae or Glomus intraradices with or without N-fixer

(Azotobacter chroococcum), Bacillus megaterium and Bacillus mucilaginous on soil

properties and the various growth parameters of Zea mays. Their applications significantly

increased the growth of Z. mays. The use of biofertilizers resulted in the highest biomass

and seedling height. Similarly, Sharma et al. (2005) studied the efficacy of native

bioinoculants, viz. AM fungi and Azotobacter separately as well as in combination for

enhancing biomass productivity of Morus alba, Populus deltoids, Psidium guajava and

Leucaena leucocephala under different agroforestry model alongwith other plant species.

Shaukat et al. (2006a) concluded that Azospirillum, Pseudomonas and Azotobacter strains

could affect seed germination and seedling growth. Ram Rao et al. (2007) studied the

influence of VAM fungi and bacterial biofertilizer (BBF) with 50% recommended dose of

(N and P) of chemical fertilizers on leafy quality traits of mulberry. The dual inoculation of

BBF and VAM (505 cut in N and P) proved economical and beneficial with regard to

saving of 50% cost of chemical fertilizers and improvement in soil fertility and leaf quality.

Similarly, Khan and Zaidi (2007) studied the synergistic effects of plant-growth promoting

rhizobacteria and an arbuscular mycorrhizal fungus (Glomus fasciculatum) on plant growth,

yield and nutrient uptake of wheat plants under field condition. The triple inoculation of

Azotobacter chroococcum with Bacillus and Glomus fasciculatum significantly increased

the dry matter by 2.6-fold as compared to the untreated control. The higher N content (33.6

mg/plant) and P content (67.8 in wheat plants) were observed with the co-inoculation of A.

chroococcum with Bacillus sp. and G. fasciculatum.The findings showed that the multiple

inoculations consistently increased the growth and yield, N and P concentrations in plants

and quality of wheat grains.

Paroha et al. (2009) further studied the integrated effects of biofertilizers (AM fungi,

Azotobacter and PSB) and NPK fertilizers in various combinations on growth and nutrient

acquisition by Tectona grandis. It was observed that integrated application of biofertilizers

and chemical fertilizers enhanced growth responses due to higher uptake of P, N, Cu, Mn

and Zn in the crops. Rabie and Humiany (2004) worked on similar pattern and revealed

that efficiency of biofertilizers can be increased using mixtures of biopreparations as

nitrogen fixers, phosphate and silicate solubilizers as well as mycorrhizal fungi.

Sakthivel et al. (2009) noted the effect of seed inoculation with PGPR on yields of

tomato. Their results favoured the above findings and reported that the higher fruit yield

was found increased in the combinations of Pseudomonas fluorescens + Azotobacter

chroococcum + Azospirillum brasilence. Ratageri and Lakshman (2009) studied the effects

of Glomus macrocarpum, Glomus fasciculatum and Azotobacter spp. on wheat (Triticum

aestivum L.) in sterilized soil. These results clearly demonstrated that the AM fungal

species with Azotobacter used in combinations were found more beneficial for much

improved growth of wheat. Similarly the seed treatments with Azotobacter enhanced seed

germination, plant height and plant biomass of wheat as compared to control (Kumar and

Gupta 2010). Sridevi and Ramakrishnan (2010) scrutinized the effects of AM fungi and

Azospirillum in single as well as dual inoculation on onion (Allium cepa L.). The two

beneficial microbes played a vital role in supplying N and P to the onion and found

enhanced growth and yield over the untreated control.

Ordookhani et al. (2010) studied the impact of inoculating the roots of tomato

(Lycopersicon esculentum) F1 hybrid GS-15 roots with PGPR and AM fungi on fruit

quality. It was found that the application of Pseudomonas + Azotobacter + Azospirillum +

AM fungi significantly increased the lycopene, antioxidant activity and potassium contents

of tomato.

Saba and Khan (2010) investigated the effect of biofertilizers (G. fasciculatum, A.

brasilense, A. chroococcum and Microphos) and pesticides in balsam. The results revealed

that individual application of biofertilizers significantly improved the plant growth

parameters such as length, dry weight and number of flowers as compared to uninoculated

plants. Arumugam et al. (2010) studied the individual and combined inoculation effects of

Rhizobium and Arbuscular mycorrhizal fungi on growth and chlorophyll content of Vigna

unguiculata L. A significant increase was observed in root and shoot length, dry weights of

root and shoot, total number of nodules, dry weight of nodules, percentage of mycorrhizal

infection and total chlorophyll content in the inoculated plants.

Rokhzadi and Toashis (2011) carried out an experiment to evaluate the effects of

single and combined inoculations with plant-promoting rhizobacteria, viz. Azospirillum,

Azotobacter, Mesorhizobium and Pseudomonas on nutrient uptake, growth and yield of

chickpea plants under field conditions. All inoculants were found superior over

uninoculated control with respect to nitrogen concentration in shoot.The treatments

containing Azospirillum + Azotobacter significantly improved phosphorus concentration in

shoots as well grain yield, biomass and, dry weight. Nitrogen and phosphorus uptake of

grains improved by applying every inoculation treatment.

Solanki et al. (2011) studied the yield and nutrient uptake by using dual inoculation

with AM fungi (Glomus fasciculatum) and Azotobacter chroococcum on Chlorophytum

bravllianum. Results showed that the nitrogen uptake was increased in Azotobacter treated

plants, while higher P and K uptake were sustained in AM fungi inoculated plants.

Economic analysis revealed the net profit was highest in NPK + Azotobacter + G.

fasciculatum using dual inoculations of micro-organisms.

Ordookhani and Zare et al. (2011) further investigated the effects of inoculation of

two cultivars of tomato (Lycopersicon esculentum) roots with PGPR and AM fungi on

growth and some element contents. The inoculations with Pseudomonas putida,

Azotobacter chroococcum and Glomus mosseae showed positive results. Azotobacter

chroococcum was more effective than Pseudomonas putida to increase all traits.

Colonization of plant roots by mycorrhiza were significantly higher than non-mycorrhizal

plants, thus increased the overall plant growth.

Effects of Azotobacter and N-fertilizers

The synergistic effect of biofertilizer like Azotobacter and N-fertilizers was well

documented in literature. The favourable effect of Azotobacter and mineral nitrogen

fertilizer on growth, chemical composition of leaves and yield was reported by Stajner et al.

(1997) on sugarbeet, Bambal et al. (1998) on cauliflower, Wyszkowska (1999) on faba bean

and Sharma (2002) on cabbage, Prabhjeet et al. (1994) on Brassica napus, Verma et al.

(1997) on cabbage, Verma et al. (2000) on pea and Panwar et al. (2000) on radish which

revealed that seed yields were found increased with their combined inoculations.

Agrawal et al. (2004) studied the effect of Azotobacter inoculation with graded doses

of nitrogen on the uptake of nutrients and yield of wheat. It was concluded that inoculation

of Azotobacter could save about 20 kg nitrogen in wheat crop. In the similar way, El-

Assiouty and Sedera (2005) carried out an experiment to study the effect of Azotobacter

chroococcum and Phosphorein singly and in combinations with different rates of N and P

chemical fertilizers on growth, yield and quality of spinach cv. Dokki. Results showed that

seed inoculations with biofertilizers (Azotobacter and Phosphorein) enriched the

rhizosphere with such micro-organisms as compared to uninoculated control. Application of

40 kg N + 15.0 kg P2O5 + 300 g phosphorein increased plants fresh yield by 27.2 and 42.3%

and 16.3 and 10.4% in seed yield over the control in the first and second seasons.

Constantino et al. (2008) evaluated the effects of two rhizobacteria (Azotobacter

chroococcum and Azospirillum) and a commercial product containing multiple strains of

arbuscular mycorrhizal fungi alongwith NPK fertilizer on the growth and yield of habanero

chilli (Capsicum chinese Jacquin) in various combinations. In the nursery phase, single

biofertilization promoted a higher growth and nutrient contents in the crop than combined

biofertilization. However in the field phase the combined biofertilization increased the

nutrient contents of the plant leaves, which were significantly greater than those observed

in the NPK treatments alone. The highest yields were recorded for the treatments involving

a single inoculation of A. chroococcum and for those with the multi-strain of AM fungi as

compared to individual inoculation of N, P and K.

Direkvandi et al. (2008) conducted an experiment to study the effects of different

rates of Nitrogen (N) fertilizer with two types of biofertilizers (0, 125, 75, 225, 125 plus

super-nitro and 125 kg N h-1 plus Nitroxin-biofertilizer) and two cultivars of tomato (Super

Chief and Super Beita) on growth and yield at field conditions. The results revealed that

there were significant differences between N level and most of the characteristics such as

plant height, leaf numbers, fruit number per inflorescence, fruit number per plant, fruit

mean weight and fruit yield. The biofertilizers improved the growth parameters such as

germination rate, plant height, leaf numbers, fruit mean weight and fruit yield. The

maximum yield was accomplished when Super Beita cultivar received 225 kg N h-1.

Similarly, Sharma et al. (2008) conducted field experiment to investigate the response of

broccoli (Brassica oleracea var. italic L.) in integrated nutrient management using organic

manure and Azotobacter alongwith synthetic fertilizers. An application of 100% NPK +

Azotobacter + 20 Mt ha-1 of CM provided the highest increase in the contents of organic C

and available N, P and K respectively. About 31, 8.4 and 12.5 kg ha-1 of N, P and K

respectively can be saved in broccoli production if CM at 20 Mt ha-1 and Azotobacter are

used in combination with synthetic fertilizers.

Premsekhar and Rajashree (2009) studied the effect of various biofertilizers on the

growth, yield parameters and quality of tomato var. CO3 under field experiment. Three

types of biofertilizers, viz., Azospirillum, Phosphate-solubilizing bacteria (PSB) and

Vesicular Arbuscular Mycorrhiza (VAM) in different combinations were tested. The results

revealed that taller plants, better yield parameters and higher yield were recorded

significantly with the application of Azospirillum + 75% N + 100% PK followed by

Azospirillum + 100% NPK. Mahato et al. (2009) carried out similar experiments to

evaluate the responses against biofertilizers and inorganic fertilizer on germination and

growth of tomato plants. Nitrogen was used as inorganic fertilizer and Azotobacter as

biofertilizer. They concluded that Azotobacter showed better results than inorganic fertilizer

in relation to seed germination and all plant-growth parameters.

Naseri et al. (2010) studied the effect of biofertilizers and yield components of

safflower under dry land conditions. Significant improvement was observed in all the

characters with applying biofertilizers and increasing nitrogen from zero to 30 kg/ha but not

30 to 60 kg/ha. There were significant interaction between nitrogen levels and bio-fertilizers

regarding yield components, seed oil and protein content. The highest yield obtained from

the treatments received 30 or 60 kg/ha with Azotobacter inoculation. The highest amount of

seed oil and protein content obtained from the multiinoculation of nitrogen, Azotobacter

and Azospirillum.

Gajbhiye et al. (2010) further studied the effects of biofertilizers (Azotobacter and

Phosphobacterium) and inorganic fertilizers (150 : 60 : 60 kg NPK/ha) on the fruit qualities

of 10 tomato cultivars and their application registered highest locule numbers per fruit,

lycopene content and vitamin-C content.

Sarkar et al. (2010) investigated the influence of nitrogen and biofertilizers on

growth and yield of cabbage. Application of both nitrogen and biofertilizer had significant

impact on growth and yield attributing characters among the different levels of

nitrogen. Application of 100 kg N ha-1 proved to be superior followed by 80 kg N ha-1.

Arumugam et al. (2010) determined the effect of Rhizobium and arbuscular

mycorrhizal fungi, both individually and concomitantly on growth and chlorophyll content

of Vigna unguiculata L. A significant increase in root length, shoot length, dry weights of

root and shoot, total number of nodules, dry weight of nodules, percentage of mycorrhizal

infection, chlorophyll a, b and total was recorded in dual inoculated plants than with

individual ones.

Keeping the importance of these bioinoculants alongwith the presence of plant

extracts Mogle (2011) conducted an experiment to study the effect of biofertilizer and leaf

extract against anthracnose disease of tomato. Results showed that the disease intensity was

significantly reduced by mixed bacterial (Azotobacter and Trichoderma) inoculation and

spray of leaf extract on plants.

Effect of bioinoculants (Azotobacter and Glomus) on nematode control

The nematodes encounter diverge group of rhizosphere microorganisms during

infestation and in many cases, this phenomena can leads to substantial disease control of the

harmful rhizosphere microorganisms. Bacteria and fungi have important roles in the

management of plant-parasitic nematodes on various crops as has been reported by Weller

(1988).

Chahal and Chahal (1988) conducted the experiment in vivo and in vitro to

determine the effects of Azotobacter chroococcum against M. incognita on brinjal. The

biofertilizer A. chroococcum significantly inhibited the hatching of egg-masses of M.

incognita and did not allow the larvae to penetrate into the roots of brinjal to form the galls.

Khan and Kounsar (2000) studied the effect of P. lilacinus, V. chlamydosporium,

Cylindrocarpon destructans, Arthrobotrys oligospora, B. subtilis, Beijerinkia indica,

Azotobacter chroococcum and Azospirillum lipoferum on the growth of mungbean (Vigna

radiata), root nodulation and root-knot disease caused by M. incognita in field experiment.

Application of bacterial and fungal bioagents significantly control the nematode

pathogenesis leading to a decrease of number of galls, egg-masses per root system and J2/kg

soil.

Siddiqui and Mahmood (2001) investigated the effects of rhizobacteria, i.e.

Pseudomonas fluorescens, A. chroococcum and A. brasilense alone and in combination with

root symbionts like Rhizobium sp. and Glomus mosseae on the growth of chickpea and

reproduction of Meloidogyne javanica. Their findings revealed that G. mosseae was found

better at improving plant growth and reducing galling and nematode reproduction than any

other organism. The effect of A. chroococcum was found more pronounced than A.

brasilense for improving growth of nematode infected plants.

Khan et al. (2002) conducted field trials to study the effect of soil application of

rhizobacteria (A. chroococcum, A. lipoferum, B. subtilis and Beijerinkia indica),

antagonistic fungi (A. oligospora, C. destructans, V. chlamydosporium and P. lilacinus)

and fenamiphos on root nodulation, plant growth, biomass production, gall formation and

reproduction of M. incognita on green gram. Their application significantly improved the

growth parameters, egg-mass production and subsequently the soil populations of M.

incognita were adversely affected.

Bansal and Verma (2002) investigated the effects of A. chroococcum inoculation on

root invasion and reproductive potential of M. javanica. The results revealed that A.

chroococcum affect nematodes development and multiplication in the host plant.

Azotobacter inoculation was partially responsible for increased plant growth in brinjal by

alleviating the damaging effect of root-knot nematode.

Chatterjee (2002) used two types of bacteria Azotobacter and Rhizobium sp. using

okra as the host plant infested with M. incognita. The results showed that among the

inoculated schedule of treatments, Azotobacter treatment significantly noticed the best

results and Rhizobium proved to be the least effective.

Jaizme-Vega et al. (2006) studied the effect of the combined inoculation of AM

fungi and PGPR on papaya infected with the root-knot nematode Meloidogyne incognita.

Results revealed that the beneficial effect due to AM inoculation persisted in the presence

of PGPR. Meloidogyne incognita infection was significantly reduced in mycorrhizal

inoculated plants. The dual inoculation of AM fungi and PGPR must be considered for

papaya plant threatened by the root-knot nematode, M. incognita.

Saravanapriya and Subramanian (2007) conducted greenhouse experiments to test

the effect of humic acid alone and in combinations with biofertilizers like Azospirillum and

phosphobacteria, biological control agents (Trichoderma viride, Pseudomonas fluorescens

and Arbuscular mycorrhizal fungus) against M. incognita on tomato. Application of humic

acid with all the bioinoculants significantly increased the plant-growth parameters and

consequently reduced the number of root-galls, egg- masses per plant and final soil

population.

Ugwuoke and Eze (2010) observed the effect of mycorrhiza (Glomus geosporum),

Rhizobium and Meloidogyne incognita on growth and development of cowpea (Vigna

unguiculata L. Walp). Their results clearly revealed that the association of mycorrhiza with

cowpea roots produced lesser galling on roots than nematode alone inoculated plants.

Pandey et al. (2011) employed eco-friendly ways of nematode management

mutualistic endophytes (Trichoderma harzianum strain, Glomus intraradices) and plant

growth promoting rhizobacteria (Bacillus megaterium and Pseudomonas fluorescens) and

assessed their effect individually and in combinations on plant biomass, oil yield of

menthol, reproduction potential and population development of root-knot nematode, M.

incognita under glasshouse conditions. These microbes enhanced the plant biomass and per

cent oil yield both with and without M. incognita inoculations.

Soliman et al. (2011) observed the influence of A. brasilense, P. fluorescens, A.

chroococcum, mixed genera of AM fungi and oxamyl for controlling Meloidogyne

incognita on Acacia farnesiana (L.) Wild and A. saligna (Labill.) in a complete randomized

design. They reported further that both oxamyl and arbuscular mycorrhiza were the most

effective treatments in decreasing the final nematode populations in both soil and roots,

number of galls and rate of buildup of root-knot nematode.

Siddiqui (2004) assessed the influence of P. fluorescens, A. chroococcum, A.

brasilense and composted organic fertilizers alone and in combinations on the

multiplication of M. incognita and growth of tomato under glasshouse experiments. Poultry

manure with P. fluorescens was the best combination for the management of M. incognita

on tomato but management of M. incognita can also be obtained if goat dung is used with P.

fluorescens or poultry manure with A. chroococcum.

Siddiqui and Futai (2009) assessed the effect of antagonistic fungi (A. niger, P.

lilacinus, P. chrysogenum) and plant-growth promoting rhizobacteria (A. chroococcum, B.

subtilis, P. putida) with cattle manure on the growth of tomato and on the reproduction of

M. incognita. Application of antagonistic fungi and PGPR alone and in combinations with

cattle manure resulted in a significant increase in the growth of nematode inoculated plants.

P. lilacinus caused highest reduction in galling and nematode multiplication followed by P.

putida, B. subtilis, A. niger, A. chroococcum and P. chrysogenum.

Khan et al. (2012) conducted an experiment to study the effect of inoculation with

biological nitrogen fixers on growth and yield of chilli ( Capsicum annum L.) cv. “Pusa

Jawala” in relation to disease incidence caused by plant-parasitic nematodes in field

condition. The growth, yield, and quality parameters of chilli increased significantly with

the inoculation of biological nitrogen fixers using Azospirillum and Azotobacter.

Performance of Azospirillum was found better as compared to Azotobacter. Simultaneous

inoculation with biofertilisers (100% recommended dose of N-fertiliser 100 kg N per ha and

farmyard manure 15 t per ha) resulted the maximum growth, yield, and quality parameters.

Thus, the associative nature of the above biofertilisers helps to save 25% nitrogenous

fertiliser in chilli crop. There was increased content in plant nitrogen, phosphate and potash,

leaf chlorophyll and residual available soil nitrogen, phosphate and potash with dual

inoculation with the biological nitrogen fixers alongwith recommended full dose of nitrogen

fertiliser. Disease intensity was recorded in decreasing order in all the treatments but more

pronounced in those where biofertilisers were added.

Role of organic matter in disease management

Organic matter plays pivotal role that affects the crop growth and yield either

directly by supplying nutrients or indirectly by modifying soil physical properties that can

improve the root environment and stimulate plant growth. Organic amendments offered an

alternative or supplementing tactic to chemical or cultural control of nematode pathogens on

agricultural crops. Considerable progress has been made in the utilization of organic matter

as soil amendment for the control of plant-parasitic nematodes (Akhtar and Mahmood,

1993c; Akhtar, 1997). Linford et al. (1938) suggested that organic amendment to soil

stimulated the activity of naturally occurring antagonists of nematode pests and argued that

the activity of these organisms provided control of plant-parasitic nematodes. The

effectiveness of oil-cakes in controlling root-knot nematodes have been documented by

several workers in different crops (Khan and Saxena, 1997; Nagesh et al., 1999).

Numerous plant species representing 57 families have been shown to contain

nematicidal compounds (Sukul, 1992). Neem (Azadirachta indica) is the best known

example by releasing many nematicidal constituents in soil. Neem plant parts like leaf, seed

kernel, seed powders, seed extracts, oil, sawdust and particularly oil-cakes have been

reported as effective for the control of several nematode species (Akhtar and Mahmood,

1996a, Akhtar, 1998). Indian farmers with no knowledge of the chemical constituents of

neem by-products have used them traditionally in pest control for centuries. Neem

constituents such as Nimbin, Salanin, thionemone, azadirachtin and various flavonoids have

nematicidal action (Thakur et al., 1981). Besides the nematicidal effects, triterpene

compounds in neem cake inhibit the nitrification process and increase available nitrogen for

the same amount of fertilizer (Akhtar and Alam, 1993a). Neem oil-seed cakes has been used

extensively in nematode control (Muller and Gooch, 1982). Other available oil-seed cakes

such as castor (Ricinus communis), groundnut (Arachis hypogaea) and Mahua (Madhuca

indica) have also been reported to be effective in nematode control (Lear, 1959 and Akhtar

and Alam, 1991).

Several environmental factors affect nematodes and soil antagonists. The addition of

organic matter to soil stimulates the activity of bacteria, fungi, algae and other

microorganisms in amended soil causes enhanced enzymatic activities (Rodriguez Kabana

et al., 1983) and accumulation of decomposition end products and microbial metabolites

which may be detrimental to plant-parasitic nematodes (Mankau and Minteer, 1962;

Rodriguez-Kabana et al., 1987). Organic amendments release some chemicals into the soil

that are directly responsible for nematode control. Rich et al. (1989) reported that ricin, a

protein derived from castor bean has nemato-toxic potential.

Metabolites produced by microbes during decomposition of organic matter can also

be detrimental to plant-parasitic nematodes. Ammonia, nitrites, hydrogen sulphide, organic

acids, and other chemicals that are produced from organic matter may be directly

nematicidal or affect egg-hatch or the mortality of juveniles (Sayre et al., 1964; Badra and

Eligindi, 1979). Badra et al. (1979) reported that plants growing in amended soil contained

greater concentrations of phenols than those growing in unamended soil and this may

induce disease resistance in roots.

Rodriguez-Kabana et al. (1987) suggested the usefulness for nematode management

by organic additives depends on their chemical compositions and the types of micro-

organisms that develop during their degradation in the soil.

In the recent years, the beneficial effects of certain types of plant derived materials

in soil have been attributed to a decrease in the population densities of plant- parasitic

nematodes (Akhtar and Mahmood, 1996b; Akhtar, 2000). During the last three decades,

several experiments have been conducted on the utility of neem oil-seed cake for

controlling nematode pests on vegetables such as tomato, eggplant, okra and a few pulse

crops (Muller and Gooch, 1982; Akhtar and Mahmood, 1996b).

The nematode population, root-galling and egg-mass production were reduced in

oil-cake amended soil, while the growth of tomato was improved which seems to be due to

reduced disease incidence (Goswami and Vijayalakshmi, 1987). Alam et al. (1980) reported

that fewer juveniles penetrated the roots of plants raised in neem cake amended soil as

compared to untreated control. The mode of action of oil-seed cakes studied by various

workers which leading to the control of plant-parasitic nematodes (Khan et al., 1974).

Tiyagi and Alam (1995) evaluated the efficiency of oil-seed cakes of neem, castor,

mustard and duan against plant-parasitic nematodes infesting mungbean and the subsequent

crop, chickpea in field trials. Several fold improvement was observed in plant-growth

parameters and the residual effects of oil-seed cakes also noted in the subsequent crop. The

population of saprophytic microorganisms increased which may arrest the potential of

pathogenic organisms.

Parveen and Alam (1999) conducted an experiment with oil-seed cakes and leaves

of neem (Azadirachta indica), castor (Ricinus communis) and rice polish, a by-product of

rice milling. All the above treatments significantly controlled Meloidogyne incognita

development and subsequently improved plant-growth parameters. The greatest

improvement was observed in plant-growth parameters of tomato by the addition of neem

cake followed by castor cake, neem leaf, castor leaf and rice polish. Both the cakes gave

better results than inorganic fertilizers (urea + superphosphate + murate of potash) as

compared to control treatment.

Rangaswamy et al. (2000) in a glasshouse experiment evaluated the efficacy of P.

penetrans and Trichoderma viride with botanicals (neem and castor cakes) in controlling

the root-knot nematode, M. incognita in tomatoes. The population of P. penetrans was

effectively controlled by neem cake however, T. viride alone or in combinations with either

neem or castor cake found to be most effective in parasitizing the egg-masses of the

nematodes.

Goswami and Sharma (2001) observed that some fungi such as Aspergillus niger, A.

terreus, F. oxysporum, F. solani, P. oxalicum and P. lilacinus were consistently associated

with egg-masses of root-knot nematode, Meloidogyne incognita in survey of tomato fields.

Both types of fungi such as saprophytic and pathogenic which grew well on medium

containing dried soobabool (Leucaena leucocephala) leaf powder, oil-seed cakes of karanj

(Pongamia pinnata) and/or neem (Azadirachta indica) and molasses were tested against M.

incognita on tomato. Combined application of the both fungal bioagents resulted in better

plant growth than either of the application of bioagents.

El-Sherif et al. (2004) reported greatest suppression in number of root-knot

nematodes, M. incognita galls per root system of sunflower. This was recorded with

sesame oil-cake mixed with oxamyl which improved plant-growth parameters. Yadav et al.

(2006) determined the efficacy of oil-seed cakes (neem, karanj, mustard, castor and mahua)

at the rate of 10, 15 and 20% w/w each as seed dressing treatments on the management of

root-knot nematode, M. incognita infesting chickpea. All the oil-cakes at different

concentrations significantly increased the plant-growth parameters and decreased the

nematode multiplication over the control. Among the oil-cakes, neem cake was the most

effective in improving growth characters and suppressing nematode infestation followed by

karanj cake. The highest concentration (20% w/w) of neem cake was more effective than

lower concentrations.

Anver (2006) found that oil-seed cakes of neem/margosa (A. indica), groundnut (A.

hypogaea), castor (R. communis), mustard (B. compestris), rocket salad/duan (Eruca sativa)

were effectively reducing the multiplication of nematodes.

Javed et al. (2007) tested two types of neem formulations for suppression of root-

galls and egg-masses of M. incognita. The crude form was neem leaves and neem cakes and

another of neem refined products “aza” the protective and curative soil application. These

formulations which significantly reduced the number of egg-masses and galls on tomato

roots.

Kalairasan et al. (2007) revealed that application of oil-cakes significantly increased

the tomato plant growth and decreased the host infestation by root-knot nematode, M.

incognita over control. Among the oil-cakes, cakes of jatropha and neem were proved to be

the best in managing the nematodes. Jatropha cake reduced the egg hatching and increased

the juvenile mortality by 14.07 and 49.33% respectively after 48 h of incubation.

Lopes et al. (2008) conducted an experiment to evaluate the role of agro-industry

wastes such as sugarcane bagasse, Saccharum spp. hybrids, coffeae husks (Coffea arabica),

castor bean oil-cake (Ricinus communis) and jackbean seed powder (Canavalio aensiformis)

applied at the rates of 0.5 or 1.0% (w/w) to control Meloidogyne javanica on tomato. Their

results revealed that jackbean seed powder was most effective in reducing the number of

root-galls and no. of eggs which was followed by castor bean oil-cakes.

Javed et al. (2008) evaluated the potential of combining P. penetrans and neem

(Azadirachta indica) formulations as a management system for root-knot nematode on

tomato. There was significant less root-galling in the P. penetrans combined with neem

cake treatment at the end of the third crop and this treatment also had the greatest effect on

the growth of tomato plants. Meena et al. (2009) assessed the biopesticidal potential of

some organic cakes, viz., neem cake, sesamum cake, mustard cake, cotton cake and castor

cake at the dose of 3 g and 5 g/pot for the management of H. cajani. Such type of amended

cakes were found significantly effective in plant growth promotion and reduction in

nematode population.

Similarly, Radwan et al. (2009) conducted a pot experiment with oil-cakes of cotton,

flax, olive, sesame and soybean at the rate of 5, 10, 15, 20 or 50 g/kg soil against

Meloidogyne incognita infecting tomato that M. incognita population in the soil and root-

galling were significantly suppressed with these cakes at all rates. All oil-cakes exhibited

varying degrees of reduction as compared to the control. The highest reduction in galls was

noted in plants treated with sesame cake whereas the lowest with olive cake.

Tiyagi et al. (2010) studied the effect of some botanicals such as Argemone

mexicana, Calotropis procera, Solanum xanthocarpum and Echhornia echinulata against

plant-parasitic nematodes and soil-inhabiting fungi infesting Trigonella foenum-graecum

under field conditions. Significant reduction was observed in the multiplication of plant-

parasitic nematodes.

Ashraf and Khan (2010) studied the efficacy of biocontrol agents (P. lilacinus and

C. oxysporum) and oil-cakes such as castor, linseed, groundnut, mahua and neem for the

management of root-knot nematode, M. javanica infecting egg-plant under glasshouse

condition. All the treatments effectively suppressed the nematode population and kept the

infection at significantly low level. The highest improvement in plant growth and best

protection against M. javanica was obtained by the integration of P. lilacinus with

groundnut cake followed by neem cake, linseed cake, castor cake and mahua cake. On the

other hand, the integration of C. oxysporum with neem cake followed by groundnut cake,

linseed cake, castor cake and mahua cake gave the best results in managing the damaging

potential of M. javanica on egg-plant.

Application of organic matter influenced soil structure, pH, nutrient and water

holding capacity alone or in combinations with mycorrhizal colonization and efficiency

(Srivastava et al., 1996). The use of AM fungi in combination with oil-cakes in

transplantable crops was found to be highly beneficial in terms of reduced nematode

infection and increased yields (Rao et al., 1997; Parvatha Reddy et al., 1997). It was found

that desirable rhizospheric changes by addition of castor cake to the soil facilitated the

effective utilization of G. fasciculatum for the management of M. incognita in tomato.

Nagesh et al. (1999) observed that mycorrhiza in combination with neem cake recorded

higher plant-growth parameters as compared to carbofuran treated plants which indicating

that the application of these combinations was superior to that of carbofuran. It has been

noted that the organic amendments tend to alter the host-parasite relationships in favour of

the crop (Jothi et al., 2003).

Various chemical substances on decomposition like ammonia, nitrites, hydrogen

sulphide, organic acids and other chemicals that are released from organic matter may be

directly nematicidal or affect egg-hatch or the mobility of juveniles (Rodriguez-Kabana,

1986). There is a direct relation between the amount of nitrogen in organic amendments and

their effectiveness as nematode population suppressors (Mian and Rodriguez-Kabana,

1982).

The magnitude of microbial stimulation and the qualitative nature of the responding

microflora and fauna depends on the nature of the organic matter added. Since organic

amendments take a long time to decompose, the nematicidal properties persisted for a

longer period, sometimes more than six months (Alam et al., 1977). Tilak and Dwivedi

(1990) found that arbuscular mycorrhizal spores exhibited the property of nitrate reducing

ability. It is likely that the symbiotic effectiveness of the arbuscular mycorrhizal fungi is

enhanced in terms of N assimilation and translocation to the host plant. Fungal hyphae may

also increase the availability of nutrients like N and P from locked sources by decomposing

large organic molecules (George et al., 1995). Rao et al. (1997) also observed that

integration of VAM fungus, G. fasciculatum with castor cake caused significant reduction

in root-galling of M. incognita on tomato. Ray et al. (1998) studied the feasibility of

interaction of VA mycorrhiza (G. fasciculatum) and castor cake (R. communis) for the

management of M. incognita on Solanum melongena. Significant improvement in

colonization of G. fasciculatum on roots of egg-plant and chlamydospore densities in this

treatment indicated favourable effects of castor cake amendment.

Borah and Phukan (2004) conducted microplot experiment to know the

compatibility of G. fasciculatum with the application of neem cake and carbofuran 3G for

integrated management of M. incognita on brinjal cv. JV-2. Vesicular arbuscular

mycorrhizal fungus, neem cake and carbofuran alone or in various combinations

significantly decreased root-knot index and nematode population in soil as compared to

nematode alone treated plants.

Pandey et al. (2005) conducted an experiment to assessed the effects of organic

amendments on activity of nematodes and microflora of chickpea rhizospheres. The results

showed that organic amendments significantly increased growth parameters of chickpea.

Higher growth of plants was recorded in neem cake amended soil. The organic amendment

significantly reduced the root-knot (M. incognita) infection but the neem cake resulted the

maximum reduction. The Rhizobium and Azotobacter population increased significantly in

such soil amended with neem cake.

Bhardwaj and Sharma (2006) studied the combined effect of AM fungi with three

different oil-cakes. The oil-cakes of Azadirachta indica, Brassica campestris and Ricinus

communis reduced the damaging potential of the root-knot nematode, Meloidogyne

incognita. Combined use of AM fungi and oil-cakes resulted in reducing the galling and

nematode multiplication, thus improving plant growth and yield. The best results pertaining

to AM root infection, nematode reproduction and plant growth and yield were obtained with

the combination of AM fungi and R. communis oil-cake.

Goswami et al. (2007) compared the percentage response of colonization and

development of a vesicular arbuscular mycorrhiza (Glomus fasciculatum) on a number of

pulse crops such as, cowpea, chickpea, soybean, pigeonpea and lentil under glasshouse

condition. The results showed that the treatments constituting FYM, karanj cake and VAM

reduced the disease incidence to a greater extent with the most promising improvement in

plant-growth parameters as compared to all other treatments.