Identification Of QTL For Resistance To Powdery Mildew In Pepper

Powdery mildew is the most common fungal disease in pepper,caused by Leveillula taurica.The fungus are both endogenous and external,and the hyphae is mainly endogenous at the early stage of infection of pepper,so it is difficult to detect the disease.When powdery mildew appears on leaves,the disease has developed to a certain extent,and it is difficult to prevent and treat with chemical agents.Breeding disease resistant variety to powdery mildew is an important way to alleviate the risk of powdery mildew in pepper production.In this study,QTL mapping of resistance to powdery mildew in pepper was completed,laying a foundation for marker-assisted breeding of resistance to powdery mildew in pepper,and accelerating the breeding of new resistant varieties to powdery mildew in pepper.In this study,susceptible parent material 83-60（C.annuum）,disease-resistant parent material H3（C.annuum）and 142 RIL（H3×83-60）F₈ generation populations were selected to develop SNP molecular markers by KASP technology and construct the genetic map.In 2016 and 2017,the incidence of powdery mildew in RIL（H3×83-60）F₈ generation group was investigated and statistically analyzed.MapQTL6.0 software was used to locate QTL.The main results are as follows:1、A genetic linkage map of pepper containing 16 linkage groups was constructed.The map contains 289 KASP markers with a total map distance of 1356.5 cM,an average map distance between markers of 4.69 cM.The length of the linkage group ranged from 19.1 to 183.6cM,and the number of markers on each linkage group was 2-44.2、In 2016 and 2017,the phenotypic identification results showed that there was a significant difference in the index of powdery mildew between the two parents.The disease index of RIL（H3×83-60）F₈ generation group showed continuous distribution.Genetic analysis of two-year phenotypic data found that the inheritance of anti-powdery mildew in RIL population was 3 pairs of additive major genes+additive polygene model in 2016.In 2017,there were 2 pairs of recessive epigenetic gene+polygenic genetic model.It indicated that the resistance of pepper powdery mildew was controlled by at least two pairs of genes,and was also controlled by some minor genes.Phenotypic analysis showed that powdery mildew resistance was a quantitative genetic trait and could be analyzed by QTL.3、Five QTL loci for powdery mildew resistance were obtained by QTL localization analysis:PMR5.1,PMR6.1,PMR9.1,PMR11.1,and PMR11.2.PMR6.1 and PMR9.1 were detected in two years,with phenotypic contribution rates were 14.6%-21.4%and 10.8%-17.3%respectively.