Analysis Of QTL And Genetic Basis Of Heterosis Of Plant Height In Wheat

Plant height is one of the important traits in wheat breeding. It is important for breeding favorable plant type with high lodging resistance and high-harvest index. Meanwhile, the mechanism is relatively simple, and easy to observe and measure, so it can be used as a model trait to investigate genetic mechanisms of quantitative traits. An"immortalized F2"(IF2) population was produced in our study, based on the population of 188 recombinant inbred lines derived from the cross between common wheat (Triticum. aestivum L.) Nongda 3338 and spelt wheat (Triticum. spelta) Altgold. We conducted research on the developmental Behavior and epistasis of plant height. The main results are as follows:1. A genetic linkage map containing 287 SSR polymorphic markers was constructed, covering a total of 3905.9 cM with an average interval of 13.6 cM. Among the 287 polymorphic markers, 70 markers showed significantly segregation distortion (P<0.05), the frequency of segregation distortion markers was 24.39%2. In RIL population, ten QTLs were detected by composite interval mapping (LOD>2.5) using multiple years and sites phenotype data of plant height, locating on chromosome 2D,4A,4B,5A, respectively, and explained variation ranged from 6.45% to 18.96%. In IF2 population, 7 QTLs were detected, with explained variation ranging from 3.00% to 14.47%. Two interval xcfd44-xgwm539 and xcau69-xgwm251 were detected both in RIL and IF2 population, and genetic effect of the QTL in the two intervals was similar. And it suggested that there was real QTL which controls plant height in the intervals.3. 11 conditional and unconditional QTLs were detected using data from five different growth stages through two-year field trials. Genetic contribute of the single QTL was from 4.81% to 16.13% at various developmental stages. As a result, plant height was affected by different QTLs at different developmental stages.4. Two heterotic loci were detected by improved composite interval mapping using over mid-parent value of the IF2 population. They were located on chromosome 4A and 6B, respectively, increasing 4.38 cm and 3.75 cm for plant height, and the total explained variation was 7.68%. Both of the two loci showed over-dominance.5. 62 significant digenic interaction pairs were identified in IF2 population by two-way ANOVA. Three types of interaction were all detected, and a ratio of them was as follows: AA:AD(DA):DD=87.1%:32.26%:11.29%.6. Each significant digenic interaction was further partitioned into four terms, in AA and AD/DA interactions, most of the best genotype was either the complementary two-locus homozygotes (11/22 or 22/11) (37.04%) or two parental genotypes (11/11 and 22/22) (40.74%). It suggested that heterozygote was not always advantageous to performance of traits.