QTLs for seedling traits under salinity stress in hexaploid wheat

<div><p>ABSTRACT: Soil salinity limits agricultural production and is a major obstacle for increasing crop yield. Common wheat is one of the most important crops with allohexaploid characteristic and a highly complex genome. QTL mapping is a useful way to identify genes for quantitative traits such as salinity tolerance in hexaploid wheat. In the present study, a hydroponic trial was carried out to identify quantitative trait loci (QTLs) associated with salinity tolerance of wheat under 150mM NaCl concentration using a recombinant inbred line population (Xiaoyan 54×Jing 411). Values of wheat seedling traits including maximum root length (MRL), root dry weight (RDW), shoot dry weight (SDW), total dry weight (TDW) and the ratio of TDW of wheat plants between salt stress and control (TDWR) were evaluated or calculated. A total of 19QTLs for five traits were detected through composite interval mapping method by using QTL Cartographer version 2.5 under normal and salt stress conditions. These QTLs distributed on 12 chromosomes explained the percentage of phenotypic variation by individual QTL varying from 7.9% to 19.0%. Among them, 11 and six QTLs were detected under normal and salt stress conditions, respectively and two QTLs were detected for TDWR. Some salt tolerance related loci may be pleiotropic. Chromosome 1A, 3A and 7A may harbor crucial candidate genes associated with wheat salt tolerance. Our results would be helpful for the marker assisted selection to breed wheat varieties with improved salt tolerance.</p></div

Island Cotton <em>Gbve1</em> Gene Encoding A Receptor-Like Protein Confers Resistance to Both Defoliating and Non-Defoliating Isolates of <em>Verticillium dahliae</em>

<div><p>Verticillium wilt caused by soilborne fungus <em>Verticillium dahliae</em> could significantly reduce cotton yield. Here, we cloned a tomato <em>Ve</em> homologous gene, <em>Gbve1</em>, from an island cotton cultivar that is resistant to Verticillium wilt. We found that the <em>Gbve1</em> gene was induced by <em>V. dahliae</em> and by phytohormones salicylic acid, jasmonic acid, and ethylene, but not by abscisic acid. The induction of <em>Gbve1</em> in resistant cotton was quicker and stronger than in <em>Verticillium</em>-susceptible upland cotton following <em>V. dahliae</em> inoculation. <em>Gbve1</em> promoter-driving GUS activity was found exclusively in the vascular bundles of roots and stems of transgenic <em>Arabidopsis</em>. Virus-induced silencing of endogenous genes in resistant cotton via targeting a fragment of the <em>Gbve1</em> gene compromised cotton resistance to <em>V. dahliae</em>. Furthermore, we transformed the <em>Gbve1</em> gene into <em>Arabidopsis</em> and upland cotton through <em>Agrobacterium</em>-mediated transformation. Overexpression of the <em>Gbve1</em> gene endowed transgenic <em>Arabidopsis</em> and upland cotton with resistance to high aggressive defoliating and non-defoliating isolates of <em>V. dahliae</em>. And HR-mimic cell death was observed in the transgenic <em>Arabidopsis</em>. Our results demonstrate that the <em>Gbve1</em> gene is responsible for resistance to <em>V. dahliae</em> in island cotton and can be used for breeding cotton varieties that are resistant to Verticillium wilt.</p> </div

<i>Gbve1</i> confers Verticillium wilt resistance in transgenic <i>Arabidopsis</i>.

<p>(A). The resistant levels of transgenic <i>Arabidopsis</i> (left panel) to <i>V. dahliae</i> was related to the expression levels of the <i>Gbve1</i> gene in the T₃ independent transgenic lines (right panel). The disease indices were presented means±SE from three replications with at least 16 plants per replication. (B). Phenotype comparison of transgenic line R5 and WT infected with <i>V. dahliae</i> isolates V991 and BP2. (C).The <i>Gbve1</i> transgenic <i>Arabidopsis</i> were resistance to <i>V. dahliae</i> through cell death response. Bar = 200 µm. (D). Expressional levels of genes relative to pathogen resistance in transgenic line R5.</p

Expression patterns of the <i>Gbve1</i> and <i>Ghve1</i> genes.

<p>(A). Expression patterns of <i>Gbve1</i>/<i>Ghve1</i> genes in H7124 (Gb) and Yumian 1 (Gh) under infection by <i>V. dahliae</i> isolate V991 and BP2. dpi means days post inoculation. (B). Expression patterns of the <i>Gbve1</i> gene by different phytohormones.</p

The <i>Gbve1</i> gene endowed Verticillium wilt resistance in cotton.

<p>(A). The cotton <i>chlI</i> gene was used as a positive control with a phenotype of yellow-colored leave after VIGS in cotton (Left: 3 weeks; Right: blossom stage). (B). The phenotypes of H7124 under infection by <i>V. dahliae</i> isolates V991 and BP2 after VIGS with CLCrV containing a fragment of <i>Gbve1</i> gene. Photos were taken at 42 d after <i>V. dahliae</i> inoculation (55 d after VIGS). (C). The disease indices <i>Gbve1</i> gene-silence lines. The results were presented as means±SE from three replications with at least 25 plants per replication. (D). Expression levels of the <i>Gbve1</i> gene and its homolog (the <i>Gbve</i> gene) in the silenced lines.</p

GUS activities in transgenic <i>Arabidopsis</i> plants containing the PGbve1:GUS construct.

<p>(A). GUS activities in the <i>Arabidopsis</i> plantlet. (B). Magnified view of vascular bundles in roots and stems.</p

<i>Gbve1</i> confers Verticillium wilt resistance in transgenic upland cotton.

<p>(A). Relative expression level of <i>Gbve1</i> genes in T₁ transgenic cotton lines. (B). The disease indices of T1 transgenic cottons with infection by <i>V. dahliae</i> defoliating isolate V991 (upper panel) and non-defoliating isolate BP2 (down panel). Results were presented as means±SE from three replications with at least 10 plants per replication. (C). The phenotypes of transgenic cotton lines with infection by <i>V. dahliae</i> isolates.</p