COMBINING ABILITY AND HETEROTIC STUDIES IN AROMATIC RICE THROUGH LINE BY TESTER ANALYSIS

Abstract

Estimating combining ability helps to evaluate genotypes and determine the nature and degree of gene activities. This study aimed to identify the best parental genotypes and superior hybrids of aromatic rice using a line × tester mating design. Five CMS (cytoplasmic male sterility) lines and four testers of local and exotic origins of aromatic rice were studied in this experiment. The unweighted pair group method with arithmetic mean (UPGMA) cluster analysis revealed genetic variability among the studied CMS and restorer lines. The analysis of variance showed that parental lines, testers, and their line by testers populations had enough genetic variability. Five out of 20 hybrids found positive heterosis for grain yield, and the hybrid BRRI1A × BUdhan2R had the maximum heterosis. In terms of the agronomic traits evaluated, specific combining ability (SCA) effects were higher than general combining ability (GCA) effects. Genotypes IR58025A, BRRI1A, and BUdhan2R were identified as superior parents based on their performances for yield traits and GCA effects in the desired direction. IR58025A × BUdhan2R and BRRI1A × BUdhan2R were chosen as promising genotypes due to their highest grain yield, heterosis, and desirable SCA. Low ratios of σ2gca/σ2sca and (σ2D/σ2A)1/2, and low to high estimations of narrow-sense heritability indicated that both additive and non-additive gene effects predominated in the inheritance of the studied traits. Pearson's correlation showed that among the 10 studied traits, grain yield plant-1 was highly significant and positively correlated with flag leaf area, spikelet fertility (%), and filled grains panicle-1, as well as, significant and negatively correlated with days to flowering and days to maturity. Superior parental genotypes and hybrids that have been identified can be employed as donor parents to improve the grain yield in aromatic rice.