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Sheath blight disease of rice caused by Rhizoctonia solani is one of the most dreaded plant diseases faced by the rice farmers all over the world. None of the commercially cultivated rice varieties have sufficient level of field resistance, and the disease is presently being managed by chemical pesticides. In this study, 40 isolates of rice sheath blight pathogen, collected from diverse rice ecosystems from 12 different states of India, were characterized for their morphological, pathological and genetic variation. The isolates showed wide morphological variation in terms of size of sclerotia and abundance of sclerotia production. The virulence of each pathogen isolate was studied on four rice varieties, that is TN1, IR 64, Tetep and Swarnadhan in glasshouse, and observations were taken by measuring the relative lesion height. The relative lesion heights produced by these isolates on four different rice varieties varied widely. Genetic variation of the isolates was analysed using ISSR markers. The primers based on AG, GA, AC and CA repeats were informative and revealed polymorphism among the isolates. The polymorphism information content ( PIC) of the primers ranged from 0.80 to 0.96, while the resolving power ( Rp) ranged from 3.7 to 15.35. Largely, grouping of the isolates happened based on their geographical origin. One isolate from Titabar, Assam, and another from Adialabad, Telangana, were quite distinct from rest of the isolates. [ABSTRACT FROM AUTHOR]

SSR markers targeting (GATA) n motifs are known to be highly polymorphic and useful in many organisms. (GATA) n motif specific SSR markers covering the whole rice genome are not available. The present study was carried out with an objective to identify class I rice microsatellites in the rice genome with (GATA)n motifs, in-silico, and validate their potential as molecular markers. A total of 243 such motifs were identified; 65 of these were present in the genic region, 59 were in the upstream region and the remaining motifs were found in the intergenic regions. Many of the (GATA) n motifs were found within and/or upstream of genes associated with biotic or abiotic stress tolerance. A total of 230 PCR-based markers targeting all the class I (GATA) n microsatellites were developed and 35 of these markers spread across the rice genome were validated in a set of 24 representative rice varieties belonging to five distinct cultivar groups. All the markers were polymorphic, with average polymorphism information content (PIC) value of 0.61, and the rice cultivars could be uniquely distinguished into different cultivar groups based on marker analysis. These informative markers targeting (GATA) n motifs representing a new set of markers in rice will be highly useful for genetic studies and marker-assisted selection. [ABSTRACT FROM AUTHOR]