Studies on Powdery Mildew of Cluster Bean Caused by Leveillula taurica (Lev.) Arn.
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Date
2018-07
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University of Agricultural Sciences, Dharwad
Abstract
Cluster bean is a versatile and multipurpose legume crop cultivated for vegetable, fodder and manure. Cluster bean powdery mildew caused by Leveillula taurica is the major limiting factor for its cultivation in India. The present investigation involving roving survey in five districts, molecular characterization of pathogen, epidemiological studies, in vitro evaluation of botanicals, bioagents and fungicides, field screening of 41 genotypes and management studies were carried out at University of Agricultural Sciences, Dharwad during the year 2017-18.
During survey maximum disease severity was observed in Dharwad (39.70 PDI) and least in Haveri district (22.92 PDI). The rDNA sequencing of L. taurica indicated that Dharwad isolate is having 94 per cent homology with Iran and Turkey isolates.
Highest conidial germination was observed at 25 °C (63.16 %) and 85 per cent relative humidity. Sowing during first fortnight of November recorded maximum disease severity. Maximum temperature was positively correlated with disease development whereas, minimum temperature, minimum and maximum relative humidity, rainfall and number of rainy days showed negative correlation. Among different botanicals and bioagents tested, maximum conidial germination inhibition was observed with nimbecidine (80.13 %) and Bacillus subtilis (56.72 %).
Among different fungicides tested, maximum inhibition was observed with hexaconazole @ 0.1 (100.00 %), wettable sulphur (95.78 %) and tebuconazole 50 % + trifloxystrobin 25 % (94.72 %). None of the genotypes were immune or resistant whereas, two, 37 and two genotypes were found to be moderately susceptible, susceptible and highly susceptible respectively. Field evaluation of fungicides revealed that two sprays of hexaconazole @ 0.1 % resulted in least PDI of 11.75 % with an yield of 6.20 t/ha and C: B ratio of 1:3.23 which was significantly superior over other treatments followed by two sprays of tebuconazole 50 % + trifloxystrobin 25 % (14.27 PDI) with an yield of 5.98 t/ha.