Combining ability test : a search for desirable traits

Evaluating the combining ability of parent line is exceptionally useful in a hybrid rice breeding program, especially when a large number of potential parental lines are available and most promising ones are to be identified on the basis of their ability to give superior hybrids. The study was conducted at PhilRice CES, to identify the combining ability of three CMS lines, 11 restorer lines, and 33 generated F1 hybrids as product of line x tester mating design. Specifically, it aimed to (a) determine the general and specific combining ability of the 14 parents for different quantitative characters, (b) measure the level of heterosis, and (c) identify the heterotic hybrids generated. Analysis of variance revealed significant differences between lines, testers, crosses, parent versus crosses and interaction between line x testers for all measured traits, therefore, further partitioning into GCA and SCA were done. As product of good line and tester combiners for different traits (GCA effect), strong positive significant effect were obtained by Milyang 23 (maturity), PR35749-HY-R and PR36246-HY-1-19-2-2R (plant height), PR36246-HY-1-19-2-2R (filled grains and total number of grains), PR34302 (panicle length), and PR36248-HY-2-5-1R and PJ23 (1000 grain weight). Only IR80559A and IR73328A for testers had positive significant effect for maturity and plant height respectively. For specific combining ability (SCA), combination of IR80559A x PR36246-HY-1-19-2-2R for plant height and IR80559A x PJ23 for spikelet fertility obtained strong positive significant effect. Among the top three hybrids, identified crossed were IR73328 A x PR36246-HY-1-19-2-2R (11373.44 kg/ha), IR68897 A x PR36248-HY-2-5-1R (10569.13 kg/ha), and IR73328 A x PR31559-AR-32-4-3-2R (10551.13 kg/ha). Correlation analysis revealed that GCA effect and per se. performance had significant positive relationship. Moreover, lines that did not show its high per se performance to all the traits can also be a good combiner.