STUDY ON VARIABILITY, SSR MARKER BASED GENETIC DIVERSITY ANALYSIS AND MARKER TRAIT ASSOCIATION IN RICE UNDER RAINFED CONDITION

Abstract

An investigation was carried out with 24 rice genotypes to identify drought tolerant genotypes at Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh during kharif season, 2018-19 in Split Plot Design with three replications. The analysis of variance revealed significant differences among the genotypes for all the characters studied. Phenotypic coefficient of variation was higher than the genotypic coefficients of variation indicating environmental influence on the traits. High heritability coupled with high genetic advance as percent of mean was observed for proline content, number of productive tillers per plant, panicle breadth and yield per plant and moderate genetic advance as percent of the mean for days to 50% flowering, panicle breadth, number of grains per plant, number of filled grains per plant, number of unfilled grains per plant and 1000 grains weight. These characters can be further used for selection of superior genotypes. Character association through correlation analysis studies revealed that the character grain yield per plant showed significant positive association with all the traits studied except 1000 grains weight in both control and drought condition. Character association through regression analysis studies revealed that the character grain yield per plant showed strongly significant positive linear association with proline content, panicle length, number of grains per plant and number of filled grains per plant in both control and drought condition and showed slightly significant positive linear relationship with days to 50% flowering, number of productive tillers per plant, panicle length and number of unfilled grains per plant in both control and drought conditions. This indicated that simultaneous selection of all these characters was important for yield improvement under drought stress conditions. Apart from morphological analyses, molecular markers (SSRs) were also applied in order to characterize these rice germplasms at DNA level. 12 SSR markers were evaluated in 24 rice varieties for molecular characterization. A total of 48 alleles were detected with an average number of alleles of 4 per locus (range 2 to 8 per locus). The marker RM303 produced the highest number of alleles per locus of eight (8 alleles). RM303 and RM304 were the best markers for identification and diversity estimation of drought tolerant rice genotypes as stated by PIC values. The gene diversity observed in this study ranged from 0.22 (RM455) to 0.84 (RM303) with an average of 0.59 which compliance with PIC values. A dendrogram revealed six clusters with a similarity coefficient of 0.15. The cultivars BRRI dhan 56 and Surjamukhi, Dular and BRRI Dhan 71, Pukhi and BRRI Dhan 56 were found far away from, and distributed around, the centroid of the cluster. Cluster I and cluster II showed maximum inter-cluster distance and thus they can be a potential parent in the future breeding programs. The structured marker trait association revealed that there were nine significant (p<0.01) marker trait associations (MTA) for six traits among the ten traits studied. These QTLs could therefore be of interest for rice breeders to use as targets to improve grain yield under drought stress through the selection of QTLs by molecular markers. The findings of this study are useful for varietal identification, thus assisting plant breeders in selecting the suitable genetically diverse parents for future crossing programs.