Wheat kernel shape and size has been under selection since early domestication. Kernel morphology is a major consideration in wheat breeding, as it impacts grain yield and quality. A population of 160 recombinant inbred lines (RIL), developed using an elite (ND 705) and a nonadapted genotype (PI 414566), was extensively phenotyped in replicated field trials and genotyped using Infinium iSelect 90K assay to gain insight into the genetic architecture of kernel shape and size. A high density genetic map consisting of 10,172 single nucleotide polymorphism (SNP) markers, with an average marker density of 0.39 cM/marker, identified a total of 29 genomic regions associated with six grain shape and size traits; ~80% of these regions were associated with multiple traits. The analyses showed that kernel length (KL) and width (KW) are genetically independent, while a large number (~59%) of the quantitative trait loci (QTL) for kernel shape traits were in common with genomic regions associated with kernel size traits. The most significant QTL was identified on chromosome 4B, and could be an ortholog of major rice grain size and shape gene GS3 or qGL3. Major and stable loci also were identified on the homeologous regions of Group 5 chromosomes, and in the regions of TaGW2 (6A) and TaGASR7 (7A) genes. Both parental genotypes contributed equivalent positive QTL alleles, suggesting that the nonadapted germplasm has a great potential for enhancing the gene pool for grain shape and size. This study provides new knowledge on the genetic dissection of kernel morphology, with a much higher resolution, which may aid further improvement in wheat yield and quality using genomic tools.

A population developed from an exotic line with supernumerary spikelets was genetically dissected for eight quality traits, discovering new genes/alleles with potential use in wheat breeding programs. Identifying new QTLs and alleles in exotic germplasm is paramount for further improvement of quality traits in wheat. In the present study, an RIL population developed from a cross of an elite wheat line (WCB414) and an exotic genotype with supernumerary spikelets (SS) was used to identify QTLs and new alleles for eight quality traits. Composite interval mapping for 1,000 kernels weight (TKW), kernel volume weight (KVW), grain protein content (GPC), percent of flour extraction (FE) and four mixograph-related traits identified a total of 69 QTLs including 19 stable QTLs. These QTLs were located on 18 different chromosomes (except 4D, 5D, and 6D). Thirteen of these QTLs explained more than 15% of phenotypic variation (PV) and were considered as major QTLs. In this study, we identified 11 QTLs for TKW (R (2) = 7.2-17.1 %), 10 for KVW (R (2) = 6.7-22.5%), 11 for GPC (R (2) = 4.7-16.9%), 6 for FE (R (2) = 4.8-19%) and 31 for mixograph-related traits (R (2) = 3.2-41.2%). In this population, several previously identified QTLs for SS, nine spike-related and ten agronomic traits were co-located with the quality QTLs, suggesting pleiotropic effects or close linkage among loci. The traits GPC and mixogram-related traits were positively correlated with SS. Indeed, several loci for quality traits were co-located with QTL for SS. The exotic parent contributed positive alleles that increased PV of the traits at 56% of loci demonstrating the suitability of germplasm with SS to improve quality traits in wheat.

Branched spike or supernumerary spikelet (SS) is a naturally occurring variant in wheat and holds great potential for increasing the number of grains per spike, and ultimately, increasing wheat yield. However, detailed knowledge of the molecular basis of spike branching in common wheat is lacking. In the present study, a recombinant inbred line (RIL) population derived from the cross of an SS accession and an elite non-SS line was developed and evaluated over four to six environments for seven SS-related traits to identify the genetic basis of SS in wheat. A framework linkage map was generated using 939 diversity arrays technology (DArT) markers. Composite interval mapping (CIM) identified a total of seven consistent quantitative trait loci (QTL) located on five chromosomes (2D, 5B, 6A, 6B, and

In wheat, exotic genotypes harbor a broad range of spike-related traits, and can be used as a source of new genes for germplasm enhancement in wheat breeding programs. In the present study, a population of 163 recombinant inbred lines was derived from a cross between an elite line (WCB414) and an exotic line (WCB617) with branched spike (supernumerary spikelet; SS) head morphology. The population was evaluated over four to six environments to identify quantitative trait loci (QTL) associated with nine spike-related traits and 10 agronomic traits. A genetic map consisting of 939 diversity arrays technology (DArT) markers was constructed. Composite interval mapping identified a total of 143 QTL located on 17 different wheat chromosomes and included 33 consistent and definitive QTL. The amount of phenotype variation explained (PVE) by individual QTL ranged from 0.61 to 91.8%. One major QTL for glume pubescence was located in a QTL-rich region on the short arm of chromosome 1A, where loci for other traits such as for kernels per spike (KS) and spike length (SL) were also identified. Similarly, a cluster of QTL associated with yield-related, agronomic and spike-related traits contributing up to 40.3% of PVE was found on the short arm of chromosome 2D, in the vicinity of a major QTL for SS-related traits. Consistent and major QTL identified in the present study may be useful in markerassisted breeding programs to facilitate transfer of desirable alleles into other germplasm. Desirable QTL alleles were also contributed by the exotic line, suggesting the possibility of enriching the breeding germplasm with alleles from SS genotypes. The wheat (Triticum aestivum L.) spike (also termed ear) is the most readily identifiable characteristic of common wheat and is the source of the primary crop product, grain. Spike architecture is defined by spikerelated traits, which contribute to pronounced phenotypic differences among wheat subspecies. For instance, the spikes of spelt wheat (T. aestivum ssp. spelta) have a long and fragile rachis, lax density with spikelets well separated from each other on the rachis, and are not free threshing (Percival, 1921;Jantasuriyarat et al., 2004). The spikes of club wheat (T. aestivum ssp. compactum) however, have a tough rachis, short length, are laterally compressed with spikelets closely packed, and are