A major and stable QTL for wheat spikelet number per spike validated in different genetic backgrounds

The spikelet number per spike (SNS) contributes greatly to grain yield in wheat. Identifying various genes that control wheat SNS is vital for yield improvement. This study used a recombinant inbred line population genotyped by the Wheat55K single-nucleotide polymorphism array to identify two major and stably expressed quantitative trait loci (QTLs) for SNS. One of them (QSns.sau-2SY-2D.1) was reported previously, while the other (QSns.sau-2SY-7A) was newly detected and further analyzed in this study.QSns.sau-2SY-7Ahad a high LOD value ranging from 4.46 to 16.00 and explained 10.21–40.78% of the phenotypic variances.QSns.sau-2SY-7Awas flanked by the markersAX-110518554andAX-110094527in a 4.75-cM interval on chromosome arm 7AL. The contributions and interactions of both major QTLs were further analyzed and discussed. The effect ofQSns.sau-2SY-7Awas successfully validated by developing a tightly linked kompetitive allele specific PCR marker in an F2:3population and a panel of 101 high-generation breeding wheat lines. Furthermore, several genes including the previously reportedWHEAT ORTHOLOG OF APO1(WAPO1), an ortholog of the rice geneABERRANT PANICLE ORGANIZATION 1(APO1) related to SNS, were predicted in the interval ofQSns.sau-2SY-7A. In summary, these results revealed the genetic basis of the multi-spikelet genotype of wheat line 20828 and will facilitate subsequent fine mapping and breeding utilization of the major QTLs.

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