Pathogenic and genetic diversity among Alternaria alternata isolates of potato from Himachal Pradesh, Madhya Pradesh and Uttar Pradesh
2017
A. JEEVALATHA, GARIMA THAKUR, V.U. PATIL | S.K. CHAKRABARTI, SANJEEV SHARMA*, V. SAGAR, B.P. SINGH,
Early blight of potato caused by species of Alternaria is one of the most important diseases of potato worldwide. The occurrence of A. solani and A. alternata varies from region to region. The samples were collected from Himachal Pradesh, Uttar Pradesh and Madhya Pradesh states of India during 2009 and 2010. The identity of all the isolates was confirmed as A. alternata by morphological characters and sequencing. PCR amplification using universal primers ITS 4 and ITS 5 resulted in an amplicon of 594 bp which showed high similarity with reference ITS sequences of A. alternata in GenBank. Analysis of sequences revealed presence of partial sequence of ITS 1 and ITS 2 and complete sequence of 5.8S rRNA gene. All the isolates of A. alternata showed 100% similarity among themselves (except ALT 43) and with other A. alternata isolates in the GenBank. Three major clusters each were obtained when isolates were genotyped for RAPD and for AFLP markers. Pathogenicity was proved by detached leaf inoculation method and all the isolates were found pathogenic with varying degree of aggressiveness. Isolates were grouped into four groups on the basis of aggressiveness. No correlation was observed between aggressiveness and the clusters made on the basis of genotyping.
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