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Presenter: J.S. Prasad, Ch. Padmavathi, R.M. Kumar, and L.V.Subba Rao Institution: Directorate of Rice Research, Hyderabad Audience: 2nd National SRI Symposium, Agartala, India Subject Country: India
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Are Nematodes a Problem in SRI?
Directorate of Rice Research, Rajendranagar, Hyderabad-500 030
J.S. Prasad, Ch. Padmavathi, R.M. Kumar, and L.V.Subba Rao
High yields of rice declined in Brazil and China after 3-4 years under aerobic conditions, possibly due to nematodes or toxic substances (Bouman, 2002).
Yield differences between aerobic and flooded rice ranged from 8 to 69%, the differences attributed to the build-up of nematodes (Peng et al., 2006).
Under controlled irrigation, even small pest problems have great impacts on yields and farmers' income.
INTRODUCTION
Uncontrolled irrigation can be associated with the rice root nematode
Hirschmanniella spp. – yield loss 8-23% (Kuriyan and Sheela, 1981)
Nematode pests that could be associated with SRI
Controlled irrigation can be associated with the root-knot nematode Meloidogyne graminicola -- yield loss 21-64 % (Rao and Biswas, 1973)
Giant cell formation induced by the root-knot nematode in phloem
Materials and methods
Field Experiment – Split Plot
Treatments: SRI, Eco-SRI, and Conventional
Varieties: Rasi and Jaya
Greenhouse studies
Treatments:
• Continuous flooding
• Optimum moisture (OM)
• Flooding & OM alternated at weekly intervals
0102030405060708090
100
Vegetative Harvest Vegetative Harvest
Rasi Jaya
Soil nematodes
Nem
ato
de
po
pu
lati
on
SRI
SRI- Eco
Conventional
H. oryzae in soil as influenced by crop establishment methods
0
50
100
150
200
250
Vegetative Harvest Vegetative Harvest
Rasi Jaya
Nem
ato
de
po
pu
lati
ion
SRI
SRI- Eco
Conventional
H. oryzae in root as influenced by crop establishment methods
Roots of freshly uprooted plant from a continuously inundated rice field
Roots showing galls developed 7 days after uprooting
Incidence of root-knot nematode at various moisture levels
Treatment No. of galls
Root volume
Root length (cm)
Root weight
(g)
Control 0.00(0.707)
1.600(1.448)
8.080(2.928)
1.280(1.333)
Continuous flooding 0.760(1.119)
1.500(1.413)
14.620(3.887)
0.682(1.084)
Optimummoisture (OM)
8.80(3.048)
1.680(1.476)
3.180(1.911)
0.650(1.072)
Alternate flooding & OM at weekly intervals
2.32(1.662)
0.820(1.145)
15.840(4.040)
0.560(1.029)
CD (p = 0.05) 0.23 0.088 0.192 0.076
Figures in parentheses indicate √X+0.5 transformed values
CONCLUSIONS
• Under aerobic or saturated conditions, more gall formation on the roots by root-knot nematode was observed
• In conventional rice cultivation, H. oryzae population is more
• In SRI fields where no water control is possible, there is need to monitor for the root nematode H. oryzae
• Existing root knot nematode infection may not express itself, but when aerobic conditions prevail, symptoms do appear
Use of cono-weeder would destroy the nematodes that have invaded the roots of weed plants
The incorporation of weeds and organic nutrients deters movement, migration and infestation by nematode pests
Decomposing organic matter promotes beneficial predatory and saprophytic nematode populations
Possible impact of SRI cultivation on plant parasitic nematodes
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