Prevalence, incidence and molecular characterization of Phomopsis vexans (Diaporthe vexans) causing leaf blight and fruit rot disease of brinjal in Karnataka (India)

Abstract

The distribution, prevalence and incidence of Phomopsis vexans in six major brinjal growing agro-climatic zones of southwest India is reported. P. vexans was isolated from diseased leaf and fruit samples from six zones and was studied for its morpho-cultural and molecular characteristics. Eighteen isolates were tested for their pathogenicity on 30-days old brinjal seedlings. The ITS regions of these fungal isolates were used for the molecular identification followed by phylogenetic analysis. The incidence of leaf blight and fruit rot disease was high in northern transition zone (NTZ: 10.625.3% and 2133.3%) followed by southern dry zone (SDZ: 8.318% and 22.362%) and central dry zone (CDZ: 1017% and 2939%). All the isolates exhibited similarities in colony morphology. Variation was observed with regard to number of pycnidia, colony growth and type. Among the 24 isolates, 18 belonged to G-type and the rest could not be ascertained to either colony type. The 18 G-type isolates produced leaf blight and fruit rot symptoms 2528 and 4555 days post inoculation, respectively. In the phylogenetic analysis, all the 24 isolates formed a single clade, thus confirming their close genetic relatedness, though they were isolated from different agro-climatic zones of southwest India. Phylogenetic analysis of complete ITS2 sequence showed the presence of two distinct groups based on substitutions and indels observed among the populations where six isolates from NDZ and CDZ formed a distinct group from the rest of the isolates.