Fine Mapping And Candidate Gene Analysis Of Powdery Mildew Resistant In Squash(Cucurbita Pepo L.)

Squash?Cucurbita pepo L.?is an important vegetable cultivar of Cucurbita.The prevalence of powdery mildew is widespread,and it is harmful to cucurbit crops,As one of the main diseases affecting the growth efficiency of squash,powdery mildew often leads to serious yield loss.Breeding resistant cultivars is the most economical and effective means to control powdery mildew,and is one of the main targets in the study of squash breeding.However,there are many physiological races of powdery mildew in squash.In addition,there are few studies on the powdery mildew resistance of squash because of the lack of resistant breeding materials.These lead to the low breeding efficiency of new disease resistant varieties and very few resistant varieties on the market.In this paper,based on the preliminary gene mapping of powdery mildew resistance gene of squash,we conducted fine mapping of resistance gene using BC₆F₂ population and re-sequencing technology,Then the prediction,cloning and expression analysis of candidate genes.These results have important significances for broadening the breeding application of candidate disease resistant genes,improving the breeding efficiency of new disease resistant varieties,reducing pesticide application,increasing planting efficiency and analyzing the molecular mechanism of disease resistance.The main results are as follows:1?High quality sequence information was obtained by re-sequencing the resistant susceptible parentsBy using the C.pepo genome sequence as reference,we re-sequenced the resistant parent63-32?P₁?and the susceptible parent inbred line 8?P₂?of the mapping population.After sequencing,9.8 Gb and 8.5Gb reads was obtained respectively.Then,the initial location area was spliced and 4.7 Mb,fine sequence was obtained.By analyzing the sequence differences between two parents,4256 In Dels and 12330 SNPs were obtained.2?The molecular markers obtained by re-sequencingn were screened,and the disease resistance gene was finely localized in the region of 157 Kb.By screening the polymorphic markers obtained by re-sequencing in 193 individuals of BC₆F₂ resistant segregating population,the disease resistance genes were gradually finely localized on the tenth chromosome between marker 836 and 356,within 157 Kb region.3?Prediction and expression analysis of candidate disease resistance genes.In combination with genome-wide annotation analysis of C.pepo,the fine mapping region contains 32 coding genes,among which chr10-29 gene has powdery mildew resistance related function and may be a candidate disease resistance gene.There is a sequence difference in the region of chr10-29 between resistant and susceptible parents,resulting in altered coding proteins.The result of tissue expression analysis showed that this candidate gene was expressed in stem and leaf.After inoculation with powdery mildew,the expression of 18h in resistant parents increased significantly.4?Marker assisted selection breeding using molecular markers associated with disease resistance gene.To cultivate of disease resistant squash inbred lines marker assisted selection breeding for resistance to powdery mildew was conducted using marker 023associated with disease resistance gene,combined with backcross breeding After screening more than 5000 individuals at seedling stage,the field observation of powdery mildew resistance was onsistent with the results of molecular marker screening.As a result,the marker can be used for marker assisted breeding and improving breeding efficiency.