PEST-LEGUME PLANT INTERACTION

Jawwad Hassan MirzaPh.D. Scholar (ID# 435108485)Acarology LaboratoryDepartment of Plant ProtectionCollege of Food and Agriculture SciencesKing Saud University, AlRiyadh, KSA

INTRODUCTION

• Important crop of Southeast Asia, Sub-Saharan Africa

• Meat of the poor• Fix atmospheric nitrogen• High quality livestock fodder• Control Soil erosion• Fresh leaves, pods and seeds consumed• High Economic Importance

• Cowpea aphid = Aphis craccivora = Bean common mosaic virus

• Whitefly = Bemesia tabaci = Mungbean yellow mosaic virus (MYMV), Cowpea mild mottle virus (CPMMV), and Bean golden yellow mosaic virus (BGYMV)

• Bean foliage beetle = Ootheca spp = Cowpea yellow mosaic virus

• Southern green stink bug = Nezara viridula = carry the spores of fungal pathogens from plant to plant, and mechanically transmit plant pathogens while feeding

• The synthesis and accumulation of a variety of storage proteins have been shown to be closely related to plant defense since several of these proteins present entomotoxic properties such as α-amylase and proteinase inhibitors, lectins and globulins. These proteins are usually present in seeds and vegetative organs of leguminous plants (Negreiros et al., 1991; Sales et al., 2000; Franco et al., 2002).

• The common• bean (Phaseolus vulgaris) presents three classes of these• insecticidal proteins, phytohemagglutinins, arcelins and• α-amylase inhibitors which comprise the bean-lectin gene• family (Moreno and Chrispeels, 1989; Chrispeels and• Raikhel, 1991). The entomotoxic effect of plant lectins• has been evaluated in different insect orders. The jack• bean (Canavalia ensiforms) lectin was shown to interfere• in insect development in both the Lepidoptera• (Lacanobia oleracea) and Hemiptera (Myzus persicae and• Rhodnius prolixus) orders (Gatehouse at al., 1999;• Ferreira-da-Silva et al., 2000).

• Vicilins, which belong to the globulin family, are• another class of storage proteins found in leguminous• seeds (Oliveira et al., 1999). They bind strongly to several• chitin-containing structures found in insect midguts and• cell walls or plasma membranes of filamentous fungi and• yeast, interfering negatively in the growth and• development of the invader organism (Sales et al., 2000).• These proteins are responsible for the resistance of• cowpea (Vigna unguiculata) seeds to Callosobruchus• maculatus (Macedo et al., 1993). Part of this resistance• could be accounted for by the low rates of vicilins• hydrolysis by the C. maculatus midgut enzymes (Sales• et al., 1992).

• Arimura et al. (2000) showed that volatiles released from

• lima bean leaves infested with Tetranychus urticae• activated the expression of different classes of defense• genes such as: lipoxygenase (LOX) via the octadecanoid• pathway, phenylalanine ammonia-lyase (PAL) in the• phenylpropanoid pathway, farnesyl pyrophosphate• synthase in the isoprene biosynthetic pathway and• pathogen-related (PR) genes in receiver leaves

• A lso, Stubblebin&e• Langenheim(1 27) foundt hat legumer

esins,w hichi ncreaseds usceptibility• of the armywormS, . exigua, to viral

infection,m ay actuallyb etterf it the• definition of toxins-small, lipid-soluble

molecule

• Difficulty in reaching concealed hosts might be overcome through the• evolutiono f longero vipositorsA. lthought his has undoubtedlyo

ccurredi n• the coevolutionaryra ce,w e areu nawareo f any casest hat

demonstrateth is• strategy.P arasitoidtsh at attackb ruchidw eevilss eemt o haveo

vercomet he• problemt hroughb ehavioraal ndp henologicaal daptationB: ruchidsf

eeding• on maturing legume seeds are protected by thick, tough seed pods;

parasitoids• may thus be adapted to attack while the pod is still young, thin, and• soft, or after it has fallen to the ground and begun to ferment (14, 15).

• Our results demonstrate that plant species richness and the

• presence of legumes in plant communities affect the life history

• of aphids and their parasitoids both directly and indirectly via

• host plant biomass and nitrogen concentration.

• In an experiment• involving pure fallows and mixtures of these legume

species, the density of snout beetles was• significantly higher in maize planted after Se. sesban þ

Cr. grahamiana compared with maize• planted after natural grass fallow. The population of

beetles was significantly positively correlated• with the amount of nitrate and total inorganic nitrogen

content of the soil and cumulative litter fall• under fallow species (Sileshi and Mafongoya, 2003).

• In the same study in eastern Zambia, Sileshi and Mafongoya (2003) recorded lower termite

• damage (% lodged plants) on maize planted after Te. vogelii þ pigeon pea, Se. sesban þ pigeon pea,

• and pure Se. sesban than maize grown after natural fallow.

• According to Rao et al. (2000), chaffer grubs, which destroy maize seedlings, increased in maize

• planted after Se. sesban fallows in Kenya. Snout beetles (Diaecoderus sp.) that breed on Se. sesban,

• pigeon pea, Cr. grahamiana, and Te. vogelii during the fallow phase attacked maize planted after

• fallows with these plant species in eastern Zambia (Sileshi and Mafongoya, 2003)

• An intensively studied example of• an inducible, indirect defense response is the synthesis• and emission of volatile organic compounds• (VOCs), which are employed in the attraction of carnivorous• insects searching for their prey(Walling, 2000;• Gatehouse, 2002; Kessler and Baldwin, 2002). The insect• feeding-induced emission of VOCs has been demonstrated• for several plant species (for overview, see• Van Poecke and Dicke, 2004), including maize (Zea• mays; Turlings et al., 1990), cotton (Gossypium hirsutum;• Ro¨se et al., 1996), lima bean (Phaseolus lunatus; Dicke• et al., 1990; Ozawa et al., 2000), and tobacco (Nicotiana• attenuata; Kessler and Baldwin, 2001).

• Nevertheless, a detergent-like• effect of exogenously added N-acyl-Glns on

the cytosolic• calcium signature in soybean cell cultures

could• be shown (Maffei et al., 2004).

• SA signals the release of plant volatiles that attract

• the natural enemies of insect pests, e.g., Lima bean and tomato

• plants infested by spider mite attract the natural enemies of spider

• mite.97

• Isoflavonoids (judaicin, judaicin-7-O-glucoside,• 2-methoxyjudaicin, and maackiain) isolated from

the wild• relatives of chickpea act as antifeedant against

Helicoverpa armigera• (Hubner) at 100 ppm. Judaicin and maackiain

were also found• to be deterrent to S. littoralis and S. frugiperda,

respectively.41

• it is clear that wounding• responses in tomato (and other Solanaceae) and Arabidopsis• are significantly different; for example, ethylene is thought to• be a positive modulator of the wounding response in tomato,• but is a negative regulator of the local response in Arabidopsis• (Stotz et al., 2000), and makes the plant more susceptible to• herbivory by a generalist herbivore, armyworm (Spodoptera• littoralis). A similar effect was observed in the legume

Griffonia• simplicifolia (Zhu-Salzman et al., 1998).

• Herbivory by a chewing insect pest,• corn earworm (Helicoverpa zea) on soya bean

is known to• result in the production of hydrogen peroxide

in the plant as• a component of induced resistance (Bi &

Felton, 1995);

• the parasitoid wasp Aphidius ervi can distinguish between

• plants infested by its host, the pea aphid (Acyrthosiphon pisum)

• and nonhost bean aphids (Aphis fabae) on the basis of emitted

• volatiles (Du et al., 1996; Powell et al., 1998).

• In• a recent study (Hughes et al. 1981), we reported

that• exposure of bean plants, Phaseolus vulgaris L., to• a low level of SO, affected feeding preference and• reproduction of the Mexican bean beetle (MBB) on• this favored host.

• Medicago truncatula is attacked by a broad range of insect herbivores including sieve-element feeders, cell content feeders, and chewing insects. In M. truncatula, genetic resistance against insects has to date been identified only against aphids: single dominant resistance genes have been identified conferring resistance against the pea aphid, bluegreen aphid, and spotted alfalfa aphid. Aphids are readily maintained in the laboratory because of their clonal reproduction, and because they can be maintained on intact plants, excised leaves, or on artificial diet. Aphid host plant resistance studies should include host selection assays, measures of aphid growth and development, and also effects on plant vigor. Direct measurements of aphid feeding behavior can also be accomplished using the electrical penetration graph (EPG) technique. Recent studies of aphid-induced gene expression in M. truncatula implicate the octadecanoid pathway in resistance against the bluegreen aphid. Bioassays of cell content feeders and chewing insects generally focus on the performance of the herbivores, measuring individual development or population growth. Defence gene expression studies have also implicated jasmonic acid signaling and the octadecanoid pathway in defence against chewing insects. Calcium oxalate crystals may also function in chewing insect defence.