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-7A had a high LOD value ranging from 4.46 to 16.00 and explained 10.21-40.78%of the phenotypic variances.QSns.sau-2SY-7A was flanked by the markers AX-110518554 and AX-110094527 in a 4.75-cM interval on chromosome arm 7AL.The contributions and interactions of both major QTLs were further analyzed and discussed.The effect of QSns.sau-2SY-7A was successfully validated by developing a tightly linked kompetitive allele specific PCR marker in an F_(2:3) population and a panel of 101 high-generation breeding wheat lines.Furthermore,several genes including the previously reported WHEAT ORTHOLOG OF APO1(WAPO1),an ortholog of the rice gene ABERRANT PANICLE ORGANIZATION 1(APO1)related to SNS,were predicted in the interval of QSns.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.

A major vernalization-independent QTL for tiller angle on chromosome arm 2BL in bread wheat

Tiller angle(TA)strongly influences plant architecture and grain yield in cereals.However,the genetic basis of TA in wheat is largely unknown.We identified three TA-related quantitative trait loci(QTL).One of them was QTa.sau-2 B-769,a major QTL localized on chromosome arm 2 BL.QTa.sau-2 B-769 was detected in seven environments,explaining 18.1%–51.1%of phenotypic variance.We developed a linked Kompetitive Allele-Specific Polymerase chain reaction(KASP)marker,KASP-AX-108792274,to further validate this locus in three additional populations in multiple environments.QTa.sau-2 B-769 increased TA by up to 24.9%in these populations.There were significant and positive correlations between TA and flag leaf angle(FLANG).However,TA was not correlated with plant height or anthesis date,suggesting that expression of QTa.sau-2 B-769 is independent of vernalization.Traes CS2 B01 G583800,a gene known to be involved in leaf angle regulation,was identified as the most likely candidate gene for QTa.sau-2 B-769.These results enrich our understanding of the mechanisms regulating wheat TA at maturity and may support precise mapping and cloning of gene(s)underlying QTa.sau-2 B-769.