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Alternaria belongs to the family of Pleosporaceae, the order of Pleosporales, the class of Dothideomycetes in the phyllum of Ascomycota. This fungal genus is characterized by its ability to produce a number of enzymes able to injured many types of crops. The symptoms of Alternaria blight on different agricultural crops such as cabbage, cauliflower, coriander, fenugreek, brinjal, onion, faba bean, dahlia, dracaena, hollyhock, carrot, marigold, tomato and wheat were observed. Alternaria produces distinctive "bulls eye" patterned leaf spots in almost all the infected plants. Nineteen Alternaria isolates were obtained from fourteen infected plant samples. The observations were recorded from the seven day old culture for colony characteristics on PDA. Based on morphology 10 isolates of Alternaria alternata, two isolates Alternaria tenuissima and Alternaria longipes and one Alternaria porri, Alternaria brassicae, Alternaria brassicicola and Alternaria sp. were identified. Alternaria species grow rapidly and produced flat, downy to woolly grayish green to black colonies. All the isolates exhibited characteristics dark-coloured multicelled conidia with longitudinal and transverse septa (phaeo-dictyospores) and a beak or tapering apical cells. DNA isolation of all isolates of Alternaria was carried out using CTAB method. Isolated DNA was subjected to amplification with ITS1 and ITS4 primers in a thermal cycler. The amplified products ranged from 580-600bp. These amplified products were sequenced and identify the species of different Alternaria isolates using BLASTn in NCBI online. All the sequences were published in NCBI public domain. The resulting sequences of all isolates were compared to other sequences in the GenBank as 90-100% identical. Genetic variability was conducted by phylogenetic analysis. |
