Investigations on Leaf Spot of Greengram Caused by Cercospora canescens Ellis and Martin
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Date
2012
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UAS, Dharwad
Abstract
Greengram [Vigna radiata (L.) Wilczek], an ancient and well known
leguminous crop of Asia, commonly called as mungbean is an important pulse crop of
India. Cercospora leafspot is of common occurrence in India. Leaf spot was noticed
in all the locations surveyed with the range of 62.25 to 86.18 per cent. The maximum
disease severity was noticed in Dharwad district (78.52%) followed by Belgaum
district (71.35%) and disease was absent in Bagalkot and Gulbarga districts.
Potato dextrose broth was used to study the growth phase of C. canescens.
Maximum dry mycelial weight was recorded on 14th day of inoculation. Maximum
mycelial growth was observed on Richard’s agar. The temperature of 250C was found
to be the best for fungal growth.
Maximum vigour index of sorghum was noticed in 16 days old culture filtrate
at 200C indicating the maximum toxin production. Among different isolates,
Amargola isolate produced more toxin with minimum vigour index. In host extract
medium, maximum colony diameter was observed in Amargola isolate and
sporulation was observed in Nippani isolate. Sporulation was observed in PDA with 6
and 8 % dextrose and maximum radial growth was observed in 6% dextrose. Among
different isolates, the large sized conidia and more number of septa were found in
Dharwad isolate.
Screening of fifty four genotypes under natural condition revealed that none of
the genotype was immune, three cultivars viz., IC 283869, R-86 and RM-8-6 were
resistant to leaf spot disease. Under in vitro condition, hexaconazole, mancozeb and
mancozeb+ carbendazim were effective fungicides. Ocimum sanctum at 15 and 20%
botanical and Trichoderma spp. were able to reduce the growth of pathogen to a
remarkable extent. In vivo studies revealed that spraying with 0.1% hexaconazole and
difenconazole helped to manage the leaf spot successfully and recorded highest yield
and yield parameters. Achook was least effective in managing the leaf spot.