Diversity and association of isolates and symptoms of spot blotch caused by Bipolaris sorokiniana of barley (Hordeum vulgare L.)

Abstract

A three year (2003-2005) survey was conducted to study the occurrence of spot blotch symptoms on barley genotypes grown in the eastern Gangetic plains of India. Nine types of symptoms were recorded. The two most prevalent symptoms were - oval to elongate surrounded by yellow margin (type A) and, narrow, elongated dark brown spots (type D). It was also observed that symptom type D changed to type A after a week from its appearance. The pathogen Bipolaris sorokiniana isolated from these symptom types were categorized in to four pathogenic groups viz., 1, 2, 3, and 5. These pathogenic groups were distributed among all symptom types. However, groups 1 and 5 were the most common and comprised of around 74% of the total spot blotch pathogen population recovered from all symptom types.