Studies on sheath blight of rice caused by Rhizoctonia solani Kuhn
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Date
2006
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD
Abstract
Rice sheath blight pathogen Rhizoctonia solani Kuhn was isolated from
the infected plants and the Koch’s postulates were proved. The disease was
characterized by ovoid spots confined to leaf sheath and leaves. The pure
culture thus obtained was used in the course of present investigation.
Host range studies were carried out on graminaceous weeds commonly
found on rice field bunds, viz., Chloris giana, Cynodon dactylon, Cyperus
rotundus, Dactylactenium aegyptium, Digitaria sanguinalis, Echinochloa
colonum, Echinochloa crusgalli, Ischaemum indicum, Paspalum conjugatum,
Panicum javanicum, Pennesetum pedicillatum. All the 11 weeds were found to
be susceptible to Rhizoctonia solani. The fungus was readily isolated from the
artificially inoculated weed plants showing the typical symptoms of the disease
and was compared with the original isolate and both of them were found
identical.
From the studies carried out on influence of the fertilizers on the
development of Rhizoctonia solani, among the different treatments it was
found that the disease was more under FYM + N application. But the basal
application of FYM + K and FYM + PK reduced the disease considerably.
This indicated that N increased the disease and K decreased the disease. So the
basal application of potassium to rice crop as a regular practice would reduce
the disease incidence considerably.
The biological antagonists Trichoderma viride, T. harzianum, T.
koningii and T. resei were strongly antagonistic to Rhizoctonia solani in dual
agar culture and seeded agar culture. In dual agar culture Trichoderma viride
showed the best antagonistic effect followed by T. koningii, T. harzianum and
T. resei.
From the in vitro evaluation of plant extracts on Rhizoctonia solani
revealed that garlic bulb extract was proved to be the best at 5 per cent level
followed by Vinca rosea. At 15 per cent eucalyptus followed by neem and
calotropis checked the growth of the Rhizoctonia solani.
Among the fungicides tested in vitro against Rhizoctonia solani by
poisoned food technique Carbendazim, Edephenphos, Hexaconazole and
Propiconazole were found most effective at 100 ppm but Thiophanate methyl
was effective at 300 ppm concentration.
By Inhibition zone technique conducted in vitro at 100 ppm level the per
cent inhibition of fungal growth was maximum in the case of Carbendazim
followed by Propiconazole, Hexaconazole, Edephenphos and Thiophanate
methyl.
In vitro evaluation of plant products against Rhizoctonia solani by
poisoned food technique revealed that coconut cake checked the growth of the
fungus at 5 per cent level followed by neem cake, groundnut cake and sesame
cake.
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Keywords
Studies, sheath, blight, rice, caused, Rhizoctonia, solani, Kuhn