Abstract
BackgroundCombining ability effects are very effective genetic parameters in deciding the next phase of breeding programs. Although some breeding strategies on the basis of evaluating combining ability have been utilized extensively in hybrid breeding, little is known about the genetic basis of combining ability. Combining ability is a complex trait that is controlled by polygenes. With the advent and development of molecular markers, it is feasible to evaluate the genetic bases of combining ability and heterosis of elite rice hybrids through QTL analysis.Methodology/Principal FindingsIn the present study, we first developed a QTL-mapping method for dissecting combining ability and heterosis of agronomic traits. With three testcross populations and a BCRIL population in rice, biometric and QTL analyses were conducted for ten agronomic traits. The significance of general combining ability and special combining ability for most of the traits indicated the importance of both additive and non-additive effects on expression levels. A large number of additive effect QTLs associated with performance per se of BCRIL and general combining ability, and dominant effect QTLs associated with special combining ability and heterosis were identified for the ten traits.Conclusions/SignificanceThe combining ability of agronomic traits could be analyzed by the QTL mapping method. The characteristics revealed by the QTLs for combining ability of agronomic traits were similar with those by multitudinous QTLs for agronomic traits with performance per se of BCRIL. Several QTLs (1–6 in this study) were identified for each trait for combining ability. It demonstrated that some of the QTLs were pleiotropic or linked tightly with each other. The identification of QTLs responsible for combining ability and heterosis in the present study provides valuable information for dissecting genetic basis of combining ability.
Highlights
Since rice (Oryza sativa L.) is a staple food for more than half of the population worldwide, the ability to increase its yield potential would be a key factor in achieving the global rice requirement of 810 million tons in 2025 [1]
The means of most of traits, except plant height (PH), heading date (HD) and seed setting rate (SS), in the TC populations were higher than the corresponding values in the BCRIL populations
The mean value of heading date of BCRIL population was lower than that of the Hua888sTC population, while higher than that of the other two TC populations. These results suggested that the three TC populations might possess a high level of special combining ability and heterosis
Summary
Since rice (Oryza sativa L.) is a staple food for more than half of the population worldwide, the ability to increase its yield potential would be a key factor in achieving the global rice requirement of 810 million tons in 2025 [1]. There have been great achievements since the first intra-subspecific hybrid rice was developed in China in 1973 [2], the yield potential of hybrid rice has apparently reached a plateau due to the limited genetic diversity [3]. Combining ability effects are very effective genetic parameters in deciding the phase of breeding programs. Some breeding strategies on the basis of evaluating combining ability have been utilized extensively in hybrid breeding, little is known about the genetic basis of combining ability. With the advent and development of molecular markers, it is feasible to evaluate the genetic bases of combining ability and heterosis of elite rice hybrids through QTL analysis
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