Evidence from principal component analysis for improvement of grain shape- and spikelet morphology-related traits after hexaploid wheat speciation

Abstract

Grain shape and size are involved in the main components of the domestication syndrome in cereals. Wheat grain shape has been dramatically altered at each stage of the domestication of tetraploid wheat and through common wheat speciation. To elucidate the evolutionary change of wheat grain shape, principal component (PC) analysis of grain shape-related traits was first conducted using wild and cultivated tetraploid, synthetic hexaploid, and common wheat accessions. The synthetic hexaploid wheat lines were previously produced through interspecific crosses between two common wheat progenitors, tetraploid wheat and Aegilops tauschii, and produced grains similar to those of cultivated tetraploid wheat. To identify genetic loci related to the difference in grain shape between common wheat and the synthetic wheat, the 15 traits related to grain and spikelet shape were measured in 108 F 2 individuals between Norin 61 and a synthetic wheat line, and the first three PC values for the 15 traits, PC1, PC2 and PC3, were mapped as quantitative traits in the F 2 population. In total, six QTLs, found on chromosomes 1A, 5A, 1D, 2D and 7D, showed significant LOD scores. Among them, a QTL for PC2, located on the 2DS chromosomal region near the Ppd-D1 locus, mainly contributed to the phenotypic difference in grain shape. Tg-D1, controlling tenacious glume phenotype, was located at a similar region to the 2DS QTL, which suggested that the Tg-D1 locus pleiotropically affects not only glume toughness but also spikelet and grain shape in hexaploid wheat. Therefore, it was predicted that wheat grains were rapidly improved toward a shorter and rounder phenotype accompanied with free-threshing wheat formation.

Quantitative trait locus analysis for flowering-related traits using two F₂ populations derived from crosses between Japanese common wheat cultivars and synthetic hexaploids

“…On the other hand, when Ldn was used as the single AB donor parent for production of synthetic wheat, D-genome variation for some morphological and physiological traits including flowering-related traits in Ae. tauschii was at least partly expressed in the hexaploid background (Kajimura et al, 2011;Okamoto et al, 2012). In the present study, QTL analyses revealed only two chromosomal regions controlling flowering-related traits in each mapping population, and failed to find any QTL previously identified using mapping populations of the synthetic hexaploid wheat lines.…”

“…tauschii to common wheat through synthetic hexaploids (Kerber, 1987;Ma et al, 1995;Mujeeb-Kazi et al, 1996). Our empirical studies using a series of wheat synthetics have also shown enriched diversity of the D genome for some morphological and physiological characters (Takumi et al, 2009;Kajimura et al, 2011;Okamoto et al, 2012). The wide variation in HT observed among Ae.…”

The cuticular wax inhibitor locus Iw2 in wild diploid wheat Aegilops tauschii: phenotypic survey, genetic analysis, and implications for the evolution of common wheat

“…WE6 and TE6 are EST-derived STS markers that are linked to Iw2 in two mapping populations [7,9]. In three of our mapping populations, linkage of the non-glaucousness loci to WE6 and TE6 were confirmed.…”

“…In common wheat ( Triticum aestivum L., 2n = 6x = 42, genome constitution BBAADD), dominant alleles W1 and W2 , control the wax production and have been assigned to chromosomes 2B and 2D, respectively [5,6]. Additionally, dominant homoeoalleles for non-glaucousness, Iw1 and Iw2 , have also been mapped to the short arms of chromosomes 2B and 2D, respectively [6-9]. Wheat plants with either the w1, w2 , Iw1 or Iw2 allele show the non-glaucous phenotype, indicating that W1 and W2 are functionally redundant for the glaucous phenotype and that a single Iw dominant allele is sufficient to inhibit the glaucous phenotype even in the presence of a W1 or W2 allele [3,6].…”

Grain morphology, texture and colour-related compounds of bread wheat cultivars in relation to cultivation regimes and growing location

“…Dubey et al (2006), using 45 morphometric features and ANN, correctly identified from 84% to 94% of the analysed wheat cultivars. The possibility of wheat cultivar discrimination / classification is the result of the inheritance of genes related to dimension and shape (Bergman et al, 2000;Okamoto et al, 2012), colour (Himi, Noda, 2005;Ficco et al, 2014) and endosperm hardness (Morris, Beecher, 2012), which accounts for the inter-cultivar differentiation. However, it is well known that these kernel features are highly affected by the conditions of plant vegetation, with the main impact being climate and fertilization regimes (Li et al, 2012;Lukow et al, 2012).…”