Spikelet number per spike (SNS) is the primary factor that determines wheat yield. Common wheat breeding reduces the genetic diversity among elite germplasm resources, leading to a detrimental effect on future wheat production. It is, therefore, necessary to explore new genetic resources for SNS to increase wheat yield. A tetraploid landrace “Ailanmai” × wild emmer wheat recombinant inbred line (RIL) population was used to construct a genetic map using a wheat 55K single- nucleotide polymorphism (SNP) array. The linkage map containing 1,150 bin markers with a total genetic distance of 2,411.8 cm was obtained. Based on the phenotypic data from the eight environments and best linear unbiased prediction (BLUP) values, five quantitative trait loci (QTLs) for SNS were identified, explaining 6.71–29.40% of the phenotypic variation. Two of them, QSns.sau-AM-2B.2 and QSns.sau-AM-3B.2, were detected as a major and novel QTL. Their effects were further validated in two additional F2 populations using tightly linked kompetitive allele-specific PCR (KASP) markers. Potential candidate genes within the physical intervals of the corresponding QTLs were predicted to participate in inflorescence development and spikelet formation. Genetic associations between SNS and other agronomic traits were also detected and analyzed. This study demonstrates the feasibility of the wheat 55K SNP array developed for common wheat in the genetic mapping of tetraploid population and shows the potential application of wheat-related species in wheat improvement programs.

Optimizing root system architecture (RSA) allows crops to better capture water and nutrients and adapt to harsh environment. Parental reproductive environment (PRE) has been reported to significantly affect growth and development throughout the life cycle of the next generation. In this study, 10 RSA-related traits were evaluated in seedling stage from five independent hydroponic tests using seeds harvested from five different PREs. Based on the Wheat55K SNP array-based genetic map, quantitative trait loci (QTL) for these traits were detected in a recombinant inbred line population. Twenty-eight putative QTL for RSA-related traits were detected, covering thirteen chromosomal regions. A major QTL, QTrl.sicau-2SY-4D for total root length (TRL), which was likely independent of PREs, explained 15.81–38.48% of phenotypic variations and was located at 14.96–19.59 Mb on chromosome arm 4DS. Interestingly, it showed pleiotropic effects on TRL, root area, root volume, root forks, root dry weight, and shoot dry weight. The functional marker KASP-Rht-D1 for Rht-D1 was used to genotype 2SY population and remapping QTL for TRL showed that QTrl.sicau-2SY-4D was not linked to Rht-D1. The kompetitive allele-specific PCR (KASP) marker, KASP-AX-110527441 linked to this major QTL, was developed and used to successfully validate its effect in three different genetic populations. Further analysis suggested that the positive allele at QTrl.sicau-2SY-4D was mainly utilized in wheat breeding of northwest China where precipitation was significantly lower, indicating that wheat requires longer TRL to capture water and nutrients in arid or semi-arid regions due to deficient precipitation. Additionally, four genes (TraesCS4D03G0059800, TraesCS4D03G0057800, TraesCS4D03G0064000, and TraesCS4D03G0064400) possibly related to root development were predicted in physical interval of QTrl.sicau-2SY-4D. Taken together, these results enrich our understanding on the genetic basis of RSA and provide a potentially valuable TRL QTL for wheat breeding.

Background: Increasing wheat yield is an urgent task to solve the global food shortage. Spikelet number per spike (SNS) is a key factor in determining kernel number per spike which has a great effect on wheat grain yield. However, modern wheat breeding narrows genetic diversity among cultivars leading to a detrimental effect on future wheat improvement. It is thus of great significance to explore new genetic resources for SNS to increase wheat yield.Results: A tetraploid landrace ‘Ailanmai’ × wild emmer wheat recombinant inbred line (RIL) population was used to construct a high-density genetic map using the wheat 55K single nucleotide polymorphism (SNP) array. The results showed that 94.83% (6204) of the mapped markers had consistent genetic and physical chromosomal locations. Subsequently, fourteen quantitative trait loci (QTL) for SNS explaining 4.23-27.26% of the phenotypic variation were identified. QSns.sau-AM-2B.3 and QSns.sau-AM-3B.2 were considered as major and novel QTL and their combination had the largest effect and increased SNS by 17.47%. In the physical intervals of QSns.sau-AM-2B.3 and QSns.sau-AM-3B.2, some development-related genes were predicted to participate in the spikelet growth and affect SNS. Additionally, significant correlations between SNS and other agronomic traits like significant and positive correlation between SNS and thousand kernel weight were detected and analyzed. Conclusions: Our study demonstrated the feasibility of wheat 55K SNP array in genetic mapping of tetraploid wheat and provided an example of exploring outstanding genetic resources from wheat related species for further utilization in common wheat improvement.

Spikelet number per spike (SNS) is a key factor in determining kernel number per spike which has a great effect on wheat grain yield. Modern wheat breeding narrows genetic diversity among cultivars leading to a detrimental effect on future wheat improvement. It is thus of great significance to explore new genetic resources for SNS to increase wheat yield. Here, a tetraploid landrace Ailanmai mult wild emmer wheat recombinant inbred line (RIL) population was used to construct a high-density genetic map using the wheat 55K single nucleotide polymorphism (SNP) array. Our results showed that the genetic and physical locations of 94.83% (6204) of the mapped markers were consistent. Subsequently, fourteen quantitative trait loci (QTL) for SNS explaining 4.23-27.26% of the phenotypic variation were identified. QSns.sau-AM-2B.3 and QSns.sau-AM-3B.2 were considered as major and novel QTL and their combination had the largest effect and increased SNS by 17.47%. In the physical intervals of QSns.sau-AM-2B.3 and QSns.sau-AM-3B.2, some development-related genes were predicted to participate in the spikelet growth and affect SNS. Additionally, significant correlations between SNS and other agronomic traits like significant and positive correlation between SNS and thousand kernel weight were detected and analyzed. Our findings demonstrated the feasibility of wheat 55K SNP array in genetic mapping of tetraploid wheat and provided an example of exploring outstanding genetic resources from wheat related species for further utilization in common wheat improvement.