Abstract
BackgroundCombining ability is a measure for selecting elite parents that make the highest contributions to hybrid performance. However, the genetic bases of combining ability and how they contributed to heterosis is seldomly known.ResultsWe constructed a both NCII and NCIII population derived from an indica-japonica cross to study the relationship among parental performance, combining ability and hybrid performance of 11 agronomic traits. Among them, specific combining ability is more important to grain yield than parental performance and general combining ability. We performed linkage analyses to phenotypic values and combining ability of all 11 traits in Doubled haploid lines and its two backcross populations and identified 108 QTLs in total. Among these QTLs, four known loci, Sd1, Ghd7, Ghd8 and DEP1 contribute a lot to GCA effects of agronomic traits except grain yield and seed setting rate. Three QTLs, Ghd8, S5 and qS12, contribute a lot to SCA effects of grain yield and present overdominace.ConclusionsOur study provides insights into the genetic bases of combining ability and heterosis and will promote the improvements of indica-japonica hybrid breeding.
Highlights
Combining ability is a measure for selecting elite parents that make the highest contributions to hybrid performance
Though a few quantitative trait locus (QTLs) contributed to combining ability has been indentified, the genetic bases of combining ability are still not clear and how they contributed to hybrid performance was totally unknown. We developed a both NCII and NCIII population derived from an indica-japonica cross, performed linkage analysis to both general combining ability (GCA) and special combining ability (SCA) effects, and explored how QTLs of combining ability contributed to hybrid performance of hybrid rice
The design of a both NCII and NCIII population The F1 generation of an indica line ZS97B (ZS97) and a japonica line Wuyugeng2 (WYG) has heterosis in PH, HD, KGW and spikelet per panicle (SP), but has hybrid weakness in seed-setting rate (SS) (Table 1). This hybrid sterility phenomenon leads to the lower yield per plant (YD) of F1 than both parents
Summary
Combining ability is a measure for selecting elite parents that make the highest contributions to hybrid performance. The potential for creating high heterosis progenies of an inbred line is called combining ability, a concept proposed by Sprague and Tatum and has been widely used in cross breeding for elite parent selection (Comstock and Robinson 1948; Griffing 1956; Sprague and Tatum 1942). The first attempt to unveil the genetic basis of combining ability was done by Griffing (1956) He proposed the methods of using diallel-cross to dissect the genetic variance into additive variance and non-additive variance, and estimated the GCA and SCA effects. His study provide theory basis for estimating genetic variance and combining ability effect in various mating design, including complete or incomplete diallel (Griffing 1956), North Carolina design (Comstock et al 1949), and top crossing (Hill et al 1998). Later study conducted transcriptome analysis and molecular markers to reveal the relationship between combining ability and genetic diversity
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