Wheat DH Population Agronomic Traits And Pre-harvest Sprouting Resistance QTL Genetic Study

Many agronomic traits of wheat, such as plant height, ear length, flag leaf length, the number of spikelet, tiller number and period of duration are quantitative trait loci (QTL) which are controlled by polygene. In the work of QTL mapping, perpetual populations are usually selected. For example, DH population is formed after chromosome doubling, every lines in the population are completely homozygous, and so that can hardly affected by the environmental factors. With this advantage, DH population that can exclude the dominant effect and can fulfill the need of the experiment in different year and different place is a good choice for QTL mapping.In this study, Y08-21and Y08-159 were selected as the parents. Chromosome doubling the anther of the F1 to develop the DH population for mapping. For genetic map construction,460 SSR and DArT markers and the software Jionmap4.0 were been used. Combined with the phenotype data of ear length, plant height, the number of spikelet, the form of awn, flag leaf length, flag leaf width, tiller number and the pre-harvest sprouting (PHS) resistance and so on, using MapQTL4.0 for QTL mapping. In this way, the genetic effect analysis can be analyzed and this may provide useful reference for wheat breeding. In order to anchor the candidate genes which can affect PHS for further expressing and regulatory network development research, some genes related to the PHS resistance were analyzed in selected lines with different PHS resistance by quantitative expression analysis. The result of the research are as follows:1. With the use of Joinmap4.0, these 460 SSR and DArT markers were used for the li-nkage map construction. These markers were assigned to 21 chromosomes of wheat inclu-ding A, B and D homologous. The total length of the genetic map is 1758.307 cM, and the average distance between makers across all genetic map was 3.822cM. The average numbe-r of markers on every chromosome was 21.09. In the chromosome 1B, there are 59 marker-s but on the D genome, the number of markers were limited.2. For QTL mapping used by the software MapQTl4.0,17 QTL have been found over two years. Of these QTLs, two QTL control the length of ear, one of them are on the chromosome 4A, in the region between wPt5108 and wPt9445 which can explain 21.8% of the phenotypic variation in 2011 and 22.3% in 2012, the other one is located in the interval between wPt2266 and wPt8957 on chromosome 2B can explain 25.1% phenotypic variatio-n in 2011. And QTLs related to the plant length also have been found on the chromosome 2B, in the interval ta0029-wpt7619 and wpt8957-wpt0981, which can explain 32.7% and 29.6% phenotypic variation respectively in 2011, and in the year 2012, that can explain 25.3% phenotypic variation in the region ta0029-wpt7619. For the number of spikelet, one QTL in the ta0214-wpt2160 located on the chromosome 2D can explain 19.9% phenotypic variation in 2011, and 19.1% in 2012. As for the length and width of the flag leaf, there are five QTLs, QTL on the chromosome 4A in the wPt1961-wPt5935, controls the length of th-e flag leaf with the rate of contribution at 19.6% in 2012, on the chromosome 2B, there are 4 QTLs can control the width of the flag leaf, the position of these QTLs were in the in-tervalsta0029-wpt7619、wpt 8957-wpt0981、wpt 5296-wpt5878 and wpt4426-wpt2266, which with the rate of contribution at 29.5%,27.6%,19.4%　and19.6%　in 2011. In the year 2011, two QTLs for the tiller have been located on the chromosome 3B (between wpt 1834 and wpt6834, can explain 16.1% phenotypic variation) and 5D (in the interval wpt0927-w pt5870, with 17.7% contribution rate). Another QTL located on the chromosome 5A, a QT L controls the form of the awn also been found in the wpt9094-wpt8182 which can explain 22.6% phenotypic variation in 2011 and 19.8% in 2012.3. With the identification for the PHS resistance in the 160 lines, both parents of the population were PHS-susceptible, but QTLs for the PHS resistance have been found on the chromosome 3 A (in 2011, there are two QTL are located in the interval wpt8699-wpt4725 and wpt2967-ta0201, which can explain 33.9% and 36.8% phenotypic variation respective-ly, and one QTL located in the interval wpt8699-wpt4725 in 2012, with the contribution rate at 22.6%). The main effect QTL in the interval wpt8699-wpt4725 was stable in the tw-o years test, the resistance gene comes from, but this parent was PHS-susceptible, so we can speculate that there must be some inhibitor genes in Y08-21 which made the resistance gene doesn’t work. On the basis of this speculate, some lines (rely on the genetic and phenotypic data), L11、L27、L47 (PHS-resistance lines), L6、L96、L117 (PHS-susceptible lines),and the parents of the DH population Y08-21,Y08-159 were selected out and with the 6 candidate genes, ABI1、AB15、VP1、AIP2、AMY3、MY2 which are related to PHS for expression difference analysis. As a result, the candidate gene VP1 and ABI5 have sign-ificant difference in these lines, because VP1 is the upstream regulatory factors of ABI5, we can draw a conclusion that VP1 is the major gene that affect the resistance of the lines.