Table_2_Overcoming Cabbage Crossing Incompatibility by the Development and Application of Self-Compatibility-QTL- Specific Markers and Genome-Wide Background Analysis.XLS

Cabbage hybrids, which clearly present heterosis vigor, are widely used in agricultural production. We compared two S5 haplotype (Class II) cabbage inbred-lines 87–534 and 94–182: the former is highly SC while the latter is highly SI; sequence analysis of SI-related genes including SCR, SRK, ARC1, THL1, and MLPK indicates the some SNPs in ARC1 and SRK of 87–534; semi-quantitative analysis indicated that the SI-related genes were transcribed normally from DNA to mRNA. To unravel the genetic basis of SC, we performed whole-genome mapping of the quantitative trait loci (QTLs) governing self-compatibility using an F2 population derived from 87–534 × 96–100. Eight QTLs were detected, and high contribution rates (CRs) were observed for three QTLs: qSC7.2 (54.8%), qSC9.1 (14.1%) and qSC5.1 (11.2%). 06–88 (CB201 × 96–100) yielded an excellent hybrid. However, F1 seeds cannot be produced at the anthesis stage because the parents share the same S-haplotype (S57, class I). To overcome crossing incompatibility, we performed rapid introgression of the self-compatibility trait from 87–534 to 96–100 using two self-compatibility-QTL-specific markers, BoID0709 and BoID0992, as well as 36 genome-wide markers that were evenly distributed along nine chromosomes for background analysis in recurrent back-crossing (BC). The transfer process showed that the proportion of recurrent parent genome (PRPG) in BC4F1 was greater than 94%, and the ratio of individual SC plants in BC4F1 reached 100%. The newly created line, which was designated SC96–100 and exhibited both agronomic traits that were similar to those of 96–100 and a compatibility index (CI) greater than 5.0, was successfully used in the production of the commercial hybrid 06–88. The study herein provides new insight into the genetic basis of self-compatibility in cabbage and facilitates cabbage breeding using SC lines in the male-sterile (MS) system.

白菜杂交种因其显著的杂种优势而广泛应用于农业生产。本研究比较了两种S5单倍型（II类）白菜自交系87-534和94-182：前者具有较高的自交不亲和性（SC），而后者具有较高的自交亲和性（SI）；对包括SCR、SRK、ARC1、THL1和MLPK在内的与SI相关的基因进行序列分析，发现87-534中的ARC1和SRK存在一些SNPs；半定量分析表明，与SI相关的基因从DNA转录到mRNA的过程正常。为揭示SC的遗传基础，我们利用由87-534与96-100杂交产生的F2群体对控制自交不亲和性的数量性状位点（QTLs）进行了全基因组定位。共检测到8个QTLs，其中三个QTLs的贡献率较高：qSC7.2（54.8%）、qSC9.1（14.1%）和qSC5.1（11.2%）。杂交组合06-88（CB201 × 96-100）产生了一个优良的杂交种。然而，由于亲本共享相同的S单倍型（S57，I类），在花蕾期无法产生F1种子。为了克服杂交不亲和性，我们利用两个自交不亲和性-QTL特异性标记BoID0709和BoID0992，以及沿九条染色体均匀分布的36个全基因组标记，在重复回交（BC）中快速引入87-534中的自交不亲和性性状。转移过程显示，在BC4F1中，重复亲本基因组（PRPG）的比例超过94%，SC植株的比例在BC4F1中达到100%。新创制的自交不亲和性系SC96-100，不仅表现出与96-100相似的农艺性状，且兼容指数（CI）超过5.0，成功应用于商业杂交种06-88的生产。本研究对白菜自交不亲和性的遗传基础提供了新的见解，并促进了在雄性不育（MS）系统中利用SC系进行白菜育种。