Search

Key Message: Major QTL on LG 1 and 3 control seed filling and seed coat development, thereby affecting seed shape, size, color, composition and weight, key determinants of crop yield and quality. A chickpea (Cicer arietinum L.) population consisting of 189 recombinant inbred lines (RILs) derived from a cross between medium-protein ICC 995 and high-protein ICC 5912 genotypes of the desi market class was analyzed for seed properties. Seed from the parental lines and RILs was produced in four different environments for determination of seed shape (SS), 100-seed weight (100-SW), protein (PRO) and starch (STA) concentration. Polymorphic genetic markers for the population were identified by Genotyping by Sequencing and assembled into a 522.5 cM genetic map. Phenotype data from the different growth environments were analyzed by QTL mapping done by single and multi-environment analyses and in addition, single marker association mapping. The analyses identified in total 11 QTL, of which the most significant (P < 0.05) loci were located on LG 1 (q-1.1), LG 2 (q-2.1), LG 3 (q-3.2, q-3.3), LG 4 (q-4.2), and LG 5 (q-5.1). STA was mostly affected by q-1.1, which explained 19.0% of the phenotypic variance for the trait. The largest QTL effects were demonstrated by q-3.2 that explained 52.5% of the phenotypic variances for 100-SW, 44.3% for PRO, and 14.6% for SS. This locus was also highly associated with flower color (COL; 95.2% explained) and showed q-3.2 alleles from the ICC 5912 parent conferred the blue flower color and production of small, round seeds with relatively high protein concentration. Genes affecting seed filling at q-1.1 and seed coat development at q-3.2, respectively, were considered to underlie differences in seed composition and morphology in the RIL population.

An in vitro spike culture method was optimized to evaluate Fusarium head blight (FHB) resistance in wheat (Triticum aestivum) and used to screen a population of ethyl methane sulfonate treated spike culture-derived variants (SCDV). Of the 134 SCDV evaluated, the disease severity score of 47 of the variants was ≤30%. Single nucleotide polymorphisms (SNP) in the UDP-glucosyltransferase (UGT) genes, TaUGT-2B, TaUGT-3B, and TaUGT-EST, differed between AC Nanda (an FHB-susceptible wheat variety) and Sumai-3 (an FHB-resistant wheat cultivar). SNP at 450 and 1,558 bp from the translation initiation site in TaUGT-2B and TaUGT-3B, respectively were negatively correlated with FHB severity in the SCDV population, whereas the SNP in TaUGT-EST was not associated with FHB severity. Fusarium graminearum strain M7-07-1 induced early expression of TaUGT-2B and TaUGT-3B in FHB-resistant SCDV lines, which were associated with deoxynivalenol accumulation and reduced FHB disease progression. At 8 days after inoculation, deoxynivalenol concentration varied from 767 ppm in FHB-resistant variants to 2,576 ppm in FHB-susceptible variants. The FHB-resistant SCDV identified can be used as new sources of FHB resistance in wheat improvement programs.

Wheat grain development is a complex process and is characterized by changes in physicochemical and structural properties of starch. The present study deals with endosperm starch physicochemical properties and structure during development in different granule-bound starch synthase I (GBSSI) null also known as waxy (Wx) genotypes. The study was conducted with pure starch isolated from wheat grains at 3-30 days post anthesis (DPA), at 3-day intervals. Amylose concentration increased throughout grain development in non-waxy (7.2-30.5%) and partial waxy genotypes (6.0-26.8%). Completely waxy genotype showed 7.0% amylose at 3 and 6 DPA, which declined during development and reached non-detectable quantities by 30 DPA. Amylopectin structure had a higher content of short chains at 3 DPA, which decreased continuously until 12 DPA, after which there were only minor changes in amylopectin chain length distribution. Similarly, the average degree of polymerization (DP) increased from 3 DPA (12.3) to 12 DPA (15.0), and then did not differ significantly up to 30 DPA (15.0). This suggests the formation of basic amylopectin architecture in wheat by 12 DPA. Wx-B and Wx-D affected amylopectin short chains mostly of DP 6-8 at 3 and 6 DPA. Wx-A affected the same fraction of chains at 9 and 12 DPA, and Wx-D affected DP 18-25 chains from 18 to 30 DPA, suggesting differential effect of waxy isoproteins on amylopectin structure formation., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Autumn-seeded winter cereals acquire tolerance to freezing temperatures and become vernalized by exposure to low temperature (LT). The level of accumulated LT tolerance depends on the cold acclimation rate and factors controlling timing of floral transition at the shoot apical meristem. In this study, genomic loci controlling the floral transition time were mapped in a winter wheat (T. aestivum L.) doubled haploid (DH) mapping population segregating for LT tolerance and rate of phenological development. The final leaf number (FLN), days to FLN, and days to anthesis were determined for 142 DH lines grown with and without vernalization in controlled environments. Analysis of trait data by composite interval mapping (CIM) identified 11 genomic regions that carried quantitative trait loci (QTLs) for the developmental traits studied. CIM analysis showed that the time for floral transition in both vernalized and non-vernalized plants was controlled by common QTL regions on chromosomes 1B, 2A, 2B, 6A and 7A. A QTL identified on chromosome 4A influenced floral transition time only in vernalized plants. Alleles of the LT-tolerant parent, Norstar, delayed floral transition at all QTLs except at the 2A locus. Some of the QTL alleles delaying floral transition also increased the length of vegetative growth and delayed flowering time. The genes underlying the QTLs identified in this study encode factors involved in regional adaptation of cold hardy winter wheat.

D hordein, a prolamin storage protein of barley endosperms, is highly homologous to the high molecular weight (HWM) glutenin subunits, which are the major determinants of bread-making quality in wheat flour. In hexaploid wheat (AABBDD), each genome contains two paralogous copies of HMW-glutenin genes that encode the x- and y-type HMW-glutenin subunits. Previously, we reported the sequence analysis of a 102-kb genomic region that contains the HMW-glutenin locus of the D genome from Aegilops tauschii, the donor of the D genome of hexaploid wheat. Here, we present the sequence analysis of a 120-kb D-hordein region of the barley genome, a more distantly related member of the Triticeae grass tribe. Comparative sequence analysis revealed that gene content and order are generally conserved. Genes included in both of these orthologous regions are arranged in the following order: a Xa21-like receptor kinase, an endosperm globulin, an HMW prolamin, and a serine (threonine) protein kinase. However, in the wheat D genome, a region containing both the globulin and HMW-glutenin gene was duplicated, indicating that this duplication event occurred after the separation of the wheat and barley genomes. The intergenic regions are divergent with regard to the sequence and structural organization. It was found that different types of retroelements are responsible for the intergenic structure divergence in the wheat and barley genomes. In the barley region, we identified 16 long terminal repeat (LTR) retrotransposons in three distinct nested clusters. These retroelements account for 63% of the contig sequence. In addition, barley D hordein was compared with wheat HMW glutenins in terms of cysteine residue conservation and repeat domain organization.