Identification of important genomic regions for foundational parent Chuanmai 42 of southwest wheat-growing zone and their genetic contribution
[Objective]Chuanmai 42,an elite wheat cultivar with high-yield potential and good adaptability,is derived from synthetic hexa-ploid wheat and has been widely used in wheat breeding program in Southwest China.By identifying the important genomic segments of Chuanmai 42 and its genetic contributions to the derivatives,the study provided molecular design basis for the breeding of breakthrough vari-eties in southwest wheat region.[Method]Chuanmai 42 and its seven derived cultivars were genotyped using 170 SSR markers and 2268 DArT markers for analyzing the distribution of Chuanm 42's genomic components and their transmissibility in Chuanmai 42-derived culti-vars.Based on constructed genetic map and the mapped QTLs for yield traits,the genetic contribution of Chuanmai 42 genomic components to seven derived varieties was identified.[Result]The distribution frequency of Chuanmai 42's genetic components were alternative in its derived cultivars.Among seven Chuanmai 42-derived 1st generation cultivars,Chuanmai 56,Chuanmai 58,Chuanmai 64,Chuanmai 104,Chuanmai 90 and Chuanmai 91 inherited more than 50％genetic components of their breeding parent Chuanmai 42,and Chuanmai 92 was less than 25％.A total of 92 introgression loci from Chuanmai 42 involved on 17 chromosomes were distributed highly among seven derived cultivars.Based on a linkage map from Chuanmai 42 containing 148 SSR and 644 DArT markers and previous-identified QTLs,eleven ge-nomic regions were found to carry QTLs for important agronomic traits on chromosomes 2A,2B,4A,4D,5B,5D,5A,6D,7A and 7D.The high-frequency introgression loci from Chuanmai 42 on chromosomes 4A,4D,5B,5D and 7D were associated with increasing grain number per spike,thousand-kernel weight and grain yield.Especially,the region of Xgwm234-Xgivm371 on chromosome 5B harbored a ma-jor QTL for thousand-kernel weight,and Chuanmai 42 haplotype increased the thousand-kernel weight by 2.21 g.The genomic regions on chromosome 4D,5D and 7D carried QTLs for increasing grain yield,with the Chuanmai 42 haplotype increasing rate of grain yield by 8.92％,6.33％,4.79％,respectively.[Conclusion]The chromosomal regions of high-frequency transmission harboring QTLs for yield-re-lated traits are deduced to be the genetic basis of Chuanmai 42 serving as a foundational breeding parent.The identification of important ge-nomic regions in Chuanmai 42 provides an important theoretical reference for breeding breakthrough wheat varieties and screening foundation-al parents in the southwest China.
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