Diversity assessment and molecular characterization of Alternaria species infecting oleiferous Brassica species from different regions

Abstract

The work was initiated to understand the spectrum of diversity in the pathogen population of Alternaria blight, one of the most ravaging fungal diseases of oilseed brassicas, resulting in up to 60% yield losses all over the world. Fifty five single spore isolates of Alternaria species (32 isolates of A. brassicae, 20 of A. brassicicola and 3 of A. alternata) were isolated from infected leaf samples collected from eight states of India and were evaluated for their morphological, cultural, biochemical, molecular and pathological characteristics. Significant variations (Plt 0.05) were observed in sporulation intensity, spore morphology, radial growth and carbohydrate concentration among the isolates of each species. Analysis of RAPD banding profiles also showed a high level of genetic diversity varying between 57-78%, 78-92% and 89-100%, among the A. brassicae, A. brassicicola and A. alternata isolates, respectively. Pathological assessment showed varied response by all the isolates on the selected host differentials ranging from highly aggressive to moderately aggressive, to non-aggressive. Extensive variations were observed in the isolates for all the parameters studied, however, no correlation could be established among various parameters. The study thus indicates that there exists a non- specific relation between the isolates interacting and infecting with different species and varieties of Brassica spread over different North West regions of India. To the best of our knowledge this is the first report of comparative evaluation of the three Alternaria species from different locations, their growth pattern on three different media and cryopreservation. newline