Assessment of Variability and Epidemiology of Curvularia Leaf Spot of Maize
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Date
2016-06
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University of Agricultural Sciences, Dharwad
Abstract
Curvularia leaf spot of maize caused by Curvularia lunata Wakker (Boedijn) is an important foliar disease which results in significant yield loss. Laboratory and field experiments were carried out to study the variability and epidemiological aspects of the disease. An intensive roving survey was carried out to know the severity of the disease. Maximum disease severity was recorded in Kerimattihalli village of Haveri district (61.20 PDI), followed by Hosalli village of the same district (53.33 PDI) and mean least severity (7.42 PDI) was recorded from Kurlageri village of Gadag district.
Among the seven solid media tested, potato dextrose agar and Czapek’s agar media were found best for the growth of C. lunata. Among the fifteen C. lunata isolates assessed for cultural, morphological and pathogenic variability studies, the isolates viz., Cl Dha and Cl Ker found highly virulent. Based on sequence comparison in NCBI (National Centre for Bioinformatics) all the ITS rDNA sequences of isolates were confirmed as C. lunata. There is high level of similarity is present among the isolates indicating less diversity.
Epidemiological studies revealed that, initially severity was low during 37th to 39th standard week and moderate during 40th to 42nd standard week. However disease progressively increased from 43rd standard week onwards and reached maximum at maturity stage (78.00 %). Maximum temperature (30.8°C - 32.4°C), minimum temperature (17.9°C - 19.3°C), with more than 85 per cent relative humidity and cumulative rainfall of 182.00 to 189.60 were very much congenial for disease development. Among weather parameters selected for correlation on development of curvularia leaf spot of maize, cumulative rainfall and maximum temperature showed significantly positive correlation. The multiple regression equation developed for PDI was Y = 37.34+4.49 X1 -11.55 X2 +1.23 X3 -0.37 X4 +0.09X5 with R2 =0.96.