Genetic diversity of rice cultivars by microsatellite markers tightly linked to cooking and eating quality

Abstract Improving cooking and eating quality of rice is one of the important objectives of many breeding programs. The study of genetic diversity in specific regions of rice genome using molecular markers is an important index that can be used for the application of marker assisted selection (MAS) in rice breeding programs. In this study, 48 rice genotypes were grouped using 7 microsatellite (SSR) markers tightly linked to major QTLs controlling three major components of rice cooking and eating quality (i.e. amylose content, gelatinization temperature and gel consistency). The number of polymorphic alleles produced by each microsatellite marker ranged from 3 alleles at RM314 locus to 10 alleles at RM276 locus. The total number of polymorphic alleles was 41 alleles with the average of 5.86 alleles per SSR locus. Effective number of alleles varied from 2.68 to 5.25 alleles at RM314 and RM276, respectively, with an average of 3.74 alleles per locus. The average heterozygosity based on Nei's gene diversity was 0.72 indicating high genetic variation among the studied varieties. Cluster analysis with UPGMA method based on simple matching (SM) similarity coefficient divided the genotypes into four groups and separated the landrace cultivars with good cooking and eating quality (based on Iranian taste) from others. Cophenetic correlation coefficient between similarity matrix and cophentic matrix was 0.93 indicating that the used similarity coefficient and cluster analysis method were suitable to use the information derived from markers to group rice genotypes. Results of this research indicated that microsatellite markers linked to genes or QTLs controlling grain cooking and eating properties are suitable tools for marker assisted selection (MAS) to identify rice grain quality

Assessment of Rice Genotypes Response to Drought Stress at the early Reproductive Stage Using Stress Tolerance Indices

Drought stress is one of the major abiotic stresses that limits rice productivity in the world. In this study 83 diverse rice genotypes were evaluated under reproductive-stage drought stress and non-stress conditions in a completely randomized design with three replications. Eleven well known stress tolerance and susceptibility indices were calculated based on the grain yield under stress and non-stress conditions. Also rank mean (RM) indices were calculated based on the ranks of genotypes for the former calculated indices. The highest seed yield under non-stress condition belonged to the genotypes Sangjo, Zenith, IR70445-146-3-3, Norin 22 and Ghasroldashti. Under stress condition, however, IR83750-131-1, IR74718-24-2-3, Sepidrood, TETEP and IR71739-24-3-5 genotypes showed the highest seed yield. STI, GMP, MRP and REI indices with positive and significant correlations with grain yield in stress and non-stress conditions were found to be the most suitable indices for selection of drought tolerant rice genotypes. According to these indices, IR83750-131-1, Sangjo, Sepidrood, Zenith and IR58 genotypes showed the highest ranks and had a higher tolerance to drought stress. Based on RM index, IR83750-131-1, IR74718-24-2-3, Sepidrod, TETEP and IR74720-13-1-2 obtained the highest ranks. Cluster analysis grouped the most drought tolerant genotypes in the second cluster