Identification of BLB resistant genes in some rice varieties for development of high yielding bacterial leaf blight tolerant types

Aim: To identify bacterial leaf blight resistant genes in some rice varieties so that these resistant varieties can be used as a good source of donor for BLB resistant genes in genetic enhancement program.Methodology: A total of sixty-one rice genotypes including resistant and susceptible checks were screened in field condition by artificial inoculation using IX020 strain of Xoo for two years (Kharif 2016 and 2017). These varieties were also genotyped for seven SSR markers tagged with major BLB resistant genes, i.e., Xa4, xa5, xa13 and Xa7. Results: In artificial screening, significant disease development was recorded and the varieties were categorized using disease scoring scale of IRRI, 1996 where seven cultivars exhibited resistance, while twenty-seven were found to be moderately resistant. In genotyping, there was distinct difference in banding position for resistant and susceptible genotypes. Genotypes having resistant disease reaction, carrying BLB resistant genes were identified. Interpretation: Genotypes IR-64, IR-68144-2b-2-2-3-1-127, Ratna, Surjamukhi, Kalinga-2, Azucena and Zheshan-2 expressed bands of RM markers closely linked to Xa4, xa5, xa13 and Xa7 BLB resistant genes and field testing also confirmed resistant host reaction against pathogens.

Haemagglutinating property & cell surface hydrophobicity of Vibrio cholerae 0139.

Cell-associated haemagglutinating activity was detected in all the epidemic strains of V. cholerae 0139 and 01, isolated in different parts of the country, with erythrocytes from rabbit, rat, chicken and guinea pig. Sheep erythrocytes were unresponsive to both groups of strains. While D-mannose, alpha-methyl-D-mannoside, glucosamine, N-acetyl-D-glucosamine, thyroglobuline were effective inhibitors of the haemagglutinating activity of the V. cholerae 0139 and 01 strains, galactose and N-acetyl-D-galactosamine sensitive haemagglutinins (HAs) were detected in the V. cholerae 01 but not in the V. cholerae 0139 strains. The best medium for expression of HAs in V. cholerae 01 and 0139 strains were observed to be penassay broth and tryptic soy broth respectively. The expression of HA in V. cholerae 01 was stimulated by Ca++ and Fe in the growth medium unlike that of V. cholerae 0139 which remained unaffected by these ions.