Genetic Analysis And Mapping Of QTLs For Wheat Resistance To Sharp Eyespot(Rhizoctonia Cerealis) By Recombinant Inbred Lines

Sharp eyespot caused by Rhizoctonia cerealis is a widespread wheat disease and resulted in severe yield and quality losses. Developing resistant varieties is an efficient solution way to control the disease. Unfortunately, the inheritance of resistance to sharp eyespot is still poorly understood so far. This study was conducted to elucidate the inheritance of resistance to sharp eyespot in a population of Fft-derived recombinant inbred lines (RILs) from a cross of 'ARz' (resistant) /'Yangmai 158' (susceptible) by using the major gene plus polygene mixed inheritance model. Response of the RILs and their parents to R. cerealis infection was evaluated in field trial by inoculating R. cerealis on cultured short toothpicks and on cooked seeds. The results indicated that two linkage major genes with additive - additive additive epistatic effect (Model B-2-1) governed the inheritance of resistance to sharp eyespot in the RILs. The recombinant rate between two major genes is about 0.1996. These two major genes showed different additive effect, one was about 10.10% and the other 2.32%. respectively. The heritability of the major genes was about 72.31%.The F6 RILs population containing 137 lines was developed from the cross ARzxyangmai 158 through the method SSD. Resistance evaluation was carried out by two methods, employing both toothpick and cooked seed with Rhizoctonia cerealisinoculation. Results indicated that the evaluation data meet the requirement to perform the mapping of QTLs. 86 pairs of SSR primer by PCR showed 97 loci with polymorphism bands among the RIL population Using marker regression analysis, 10 SSR markers associated with sharp eyespot resistant QTLs were found based on the disease index from two inoculation methods. 11 linkage groups were constructed on 2, 3, 7 homoeologous group chromosomes using MapMaker3.0. 3 resistance QTLs (LOD>2.3) to sharp eyespot in wheat were detected on 3B(one), 7D(two) chromosomes by one-factor analysis method and compound interval mapping repeatedly. Each QTL could explain 6.93%, 48.97% and 14.36% of the phenotypic variance, respectively. We consider at least one major QTL resistance to wheat sharp eyespot was located on 7D chromosome.In order to connect the relationship of SSR markers with sharp eyespot resistance in wheat. 5 SSR markers selected by one-factor analysis method were testified in two different samples. One contained the offsprings derived from hybrids of ARz with different parents, the other including 4 resistant and 4 susceptible varieties. Based on the result of the first sample, genotypes in higher generations are showed in accord with their disease indices. While some polymorphism bands for 4 resistant varieties are not completely identical with ARz as resistant, polymorphism bands of 4 susceptible varieties also showed difference with Yangmai 158 as susceptible parent in the second sample. However, the tendency of polymorphism bands appeared in ARz can still be observed in other resistance genotypes, in the same way, the bands associated with Yangmai 158 were also found in other susceptible varieties.