PHENOTYPIC AND MOLECULAR VARIABILITYAMONG ALTERNARIA SOLANI CAUSING POTATOEARLY BLIGHT IN GUJARAT, INDIA

Abstract

Early blight, caused by Alternaria solani, is an important foliar disease of potato andcan cause substantial yield losses. This study assessed phenotypic and molecular variability amongthirty-six A. solani isolates collected from major potato-growing regions of Gujarat, India. Thirty-sixAlternaria isolates obtained from six major potato-growing districts of Gujarat exhibited substantialcultural, morphological and molecular variability. Conidial dimensions varied from 12.5–89.4 √4.6–30.5 μm on potato dextrose agar and from 12.1–82.4 √ 4.1–27.7 μm on Richard’s agar. ITS1/ITS4amplification and sequencing of representative isolate As1 produced an amplicon of approximately 540bp and showed 98–99% similarity with A. solani sequences in Gen Bank, supporting its identification.RAPD analysis of all 36 isolates using five informative primers generated 30 scorable loci, of which28 were polymorphic (93.3%). UPGMA analysis resolved the isolates into two major clusters. AMOVAattributed 20% of molecular variation to differences between the two geographic populations and80% to variation within populations. The results demonstrate substantial phenotypic and RAPD-basedgenetic variability in the Gujarat isolate collection and provide baseline information relevant topathogen surveillance, resistance breeding and early-blight management.