Prevalence and biology of Cercospora sojina causing frogeye leaf spot disease of soybean in HimachalPradesh

摘要

Present investigation was conducted with the aim to generate information on the status of frogeye leaf spot disease of soybean and standardize the techniques of isolation, growth, sporulation for its causal agent Cercospora sojina. The status and distribution of frogeye leaf spot (FLS) of soybean was assessed in major soybean growing districts of Himachal Pradesh. The disease severity ranged between 0.50 to 66.7 per cent, maximum being at Palampur (66.8%) followed by Nagari (55.6%) areas of Kangra district, whereas it was minimum at Bajaura and Kalehli (0.5%) areas of Kullu district. Disease symptoms of FLS were described based on samples from infected plants in field and artificial inoculation under green house conditions. Seven isolates were raised from samples collected during survey and their pathogenicity was proved. They were further identified on the basis of morpho-cultural features. Potato dextrose cellulose agar (PDCA) was found best culture medium for the growth and sporulation of C. sojina followed by soybean flour agar and potato dextrose agar as compared to other media whereas, soybean leaf extract agar media was found best for sporulation of C. sojina followed by Potato dextrose cellulose agar. Effect of different temperature levelson mycelial growth and sporulation was studied and 25"C temperature was found optimum temperature for both mycelial and sporulation of pathogen. Effect of different pH levels revealed that pH in the range of 6.5-7.5 was optimum for growth and sporulation of the pathogen. Study on effect of three different light regimes on growth and sporulation of C. sojina revealed that maximum mycelial growth was observed under continuous dark conditions whereas, continuous light conditions favoured sporulation of the pathogen.