Variability in cauliflower stalk rot pathogen Sclerotinia sclerotiorum

Abstract

Genetic and pathogenic variability of Sclerotinia sclerotiorum causing stalk rot of cauliflower were studied. Ten isolates collected two from each of the five states namely Chhattisgarh (Ch1, Ch2), Delhi (D1, D2), Himachal Pradesh (HP1, HP2), Uttaranchal (U1, U2) and West Bengal (WB1, WB2) were used to study genetic variability of S. sclerotiorum infecting cauliflower in terms of Mycelial Compatibility Groups (MCGs). Four arbitrary MCGs were formed based on compatible and incompatible reaction. MCG 3 comprised of four isolates and the other MCGs (MCG 1, 2 AND 4) comprised of two isolates each. Isolates belonging to one MCG were compatible among each other but incompatible to isolates belonging to other MCGs. In terms of pathogenicity a narrow range of disease index values were obtained from the ten isolates. Highest disease index value of 36.1 was recorded with U1 isolate followed by D1 isolate when tested on cauliflower variety Pusa Synthetic in an artificial epiphytotic condition. The lowest disease index value of 28.9 was recorded with WB1 isolate. Based on pathogenicity reaction three groups were formed out of ten isolates. Isolates belonging to ten MCG differed significantly in terms of pathogenicity.