Identification and Genetic Diversity Analysis of Ascochyta Species Associated with Blight Complex of Pea in a Northwestern Hill State of India

Abstract

Forty isolates of Ascochyta spp. infecting pea collected from different commercial pea growing areas of Himachal Pradesh were characterized into three species—Ascochyta pinodes, A. pisi and A. pinodella—based on symptoms, morphological and cultural traits. The identity of the isolates was confirmed by studying the rDNA sequence patterns. Based on various cultural and morphological trait combinations, 36 isolates were identified as A. pinodes, one isolate as A. pisi and one isolate as A. pinodella. Whereas two isolates, As3 and As14, could not be placed in any of the species as equal number of characters matched with A. pisi and A. pinodes. However, sequencing of ITS region of these isolates resolved the ambiguity and placed them in A. pinodes. This necessitates ITS sequencing as one of the criteria to establish the taxonomic status of Ascochyta species infecting pea. RAPD, RAMS, and Rep-PCR analysis with 10, 4 and universal ERIC, and BOX-AIR primers categorized different isolates according to their geographical locations. This study established the predominance of A. pinodes in Himachal Pradesh where edible pea is one of the remunerative off-season vegetable crops. This also constitutes first report of genetic variability of Ascochyta species infecting pea in India.