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The bacterial leaf blight of rice caused by Xanthomonas oryzae pv. oryzae is one of the most devastating pathogenic diseases responsible for extensive crop loss across different rice growing regions of the world. Presently, new X. oryzae strains have emerged which have managed to overcome the resistance conferred by major genes like xa5 and xa13. Under such circumstances the current paper evaluates rice genotypes belonging to diverse origins, viz. high yielding varieties, indigenous landraces and IR24 near isogenic lines, in terms of their resistance against three widely available strains of X. oryzae in India vis-à-vis West Bengal. The genotypes were also screened using molecular markers which are tightly linked with four major resistance conferring genes, namely Xa4, xa5, xa13 and Xa21. The overall analysis revealed that the three gene combination i.e.xa5 + xa13 + Xa21 was essential for maintaining stability in resistance against all the three pathogenic strains used for inoculation in the current study. A deviation from the above mentioned gene combination resulted in variable degree of pathogenesis, depending upon the Xoo strain used for inoculation. The investigation also identified the presence of dominant Xa4 gene among many of the popular cultivars in West Bengal, as well as in indigenous landraces like Kalabhat and Chamarmani; which showed strong resistance against the local Xoo strain. However, the genotypes failed to show any significant resistance against newly introduced strains indicating that the popular cultivars in West Bengal are still vulnerable towards new pathogenic strains of Xanthomonas oryzae. Thus, introgression of multiple resistance gene into popular cultivars in the region is necessary for ensuring durable resistance against the disease. [ABSTRACT FROM AUTHOR]

Eighty one rice genotypes were studied using 30 SSR markers and data obtained were analyzed using STRUCTURE software which classified the population into two sub groups or subpopulations, designated as subpopulation 1 and 2. Subpopulation 1 mostly comprised of 60 germplasms majority of which are Indica in origin, whereas subpopulation 2 mostly comprised of tropical and temperate Japonica subspecies. Cluster analysis was performed using UPGMA and Dendrogram was constructed which consisted of 4 clusters comprising of Indica accessions in majority and 3 clusters of tropical and temperate Japonica subspecies, thereby suggesting large diversity in the population. [ABSTRACT FROM AUTHOR]

The current study extensively evaluates 51 genotypes for their fertility restoration potential using test crosses with five WA (wild abortive) Cytoplasmic Male Sterile lines namely IR58025A, IR6897A, IR79156A, IR80559A and APMS6A. Also the genotypes were screened using SSR markers RM6100 and RM10313, tightly linked with the fertility restorer genes Rf4 and Rf3 respectively. The two way approach helped in identifying potential restorers for five WA-CMS lines and also detected the presence of dominant Rf genes in their genetic background. The R-lines identified can be safely presumed to be strong restorers for consecutive A-lines they were crossed with. The study also identified a potential maintainer CN1039-9 for the A-line IR58025A. The maintainer line identified can be later exploited for developing new CMS lines. [ABSTRACT FROM AUTHOR]