Characterization of Alternaria brassicae causing black leaf spot disease of cabbage (Brassica oleracea var. capitata) in the southern part of Kazakhstan

Abstract

Cabbage plants showing symptoms of leaf spot were detected from various fields in the Almaty region of Kazakhstan in the winter seasons of 2015 and 2016. The disease incidences of approximately 50% were recorded in various fields visited in the Almaty region. The pathogen was aseptically isolated from the symptomatic leaves and maintained in an in vitro culture media. Morphological characteristics and sporulation of the fungus was determined under both light and electron microscopy. The extracted genomic DNA of the fungi was subjected to Polymerase Chain Reaction (PCR) using ABCsens/ABCrev and ITS1/ITS4 primers amplifying ABC transporter (Atr1) gene and the internal transcribed spacer regions, respectively. The amplified products of PCR were sequenced, aligned, blasted and compared for similarity with other species in the NCBI GenBank. The cluster analysis result showed 99% homology with related fungi retrieved from the NCBI GenBank for the ITS region. The fungal isolate was pathogenic towards twenty-two-day-old plants, namely, Brassica oleracea, Lycopersicon esculentum, Solanum melongena, and was established as the causal agent of leaf spot on these plants. This is the first record implicating A. brassicae for black leaf spot disease of cabbage in Kazakhstan.