Studies on the management of black scurf of potato caused by rhizoctonia solani kuhn.
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Date
2005
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Publisher
CCSHAU
Abstract
The fungus Rhizoctonia solani Kuhn causing black scurf of
potato was isolated and purified. Among seven bioagents evaluated in
vitro against R. solani by dual culture method fungal bioagents viz.,
Trichoderma viride, T. harzianum and G. virens showed their maximum
potential at lower pH (5 and 6) while bacterial bioagents viz.,
Pseudomonas fluorescens, P. maltophila, Bacillus subtilis and
Azotobacter chroococcum were more active in the alkaline range.
However, T. viride was effective in wide pH range. Similarly when
bioagents were tested at different temperature regimes P. maltophila
and T. viride showed their potential over a wide temperature range
while others were effective in the temperature range of 20-30 oC. On
the basis of antagonistic potential of bioagents in vitro five bioagents
were selected for evaluation in the field both as seed and soil
treatment. Best results in terms of reduction of disease severity were
obtained in case of P. maltophila and T. viride. Further both the
antagonists increased the tuber yield appreciably in comparison to
check. Plant height was not affected by these treatments. Tubertreatment done with few resistance inducing chemicals viz., indole
acetic acid, indole butyric acid, salicylic acid, nicotinic acid and
benzoic acid at 0.125 and 0.25 per cent concentrations revealed
salicylic acid to be most effective in reducing the disease followed by
nicotinic acid. At 0.125 per cent concentration reduction in plant
height was noticed on IAA and IBA at 30 days after sowing which
recovered at 60 days after sowing. Effect of these chemicals on tuber
yield were not well marked.