| Cucurbita pepo L.belongs to the Cucurbita genus Cucurbita.It is an annual herb with abundant nutrients,high yield,high edible and medicinal value.,and is widely cultivated.Powdery mildew is one of the important diseases in the Cucurbita pepo L.production,which is common occurred all over the world.The occurrence of powdery mildew affects the growth of Cucurbita pepo L.crops.In the later stage of the disease,the photosynthesis is not available to provide nutrients for Cucurbita pepo L.,result in insufficient grain,fruit yield and quality decline during harvest.At present,the prevention and control of Cucurbita pepo L.powdery mildew is mainly based on chemical control.However,chemical fungicides are easy to pose a threat to the environment and human health,it can also cause resistance to powdery mildew and increase the difficulty of prevention.Isolation and cloning of Cucurbita pepo L.powdery mildew resistance ralated gene,and breeding of resistant varieties by Marker-assisted selection(MAS)became one of the main research directions of Cucurbita pepo L.breeding.In this study,the pathogens and physiological races of Cucurbita pepo L.powdery mildew were identified,and the interaction between pathogens and Cucurbita pepo L.was explored.The resistance identification of 64 germplasm resources was carried out.From the identified anti-pathogenic materials,the powdery mildew high resistance inbred line'X10'and the high-sensitivity inbred line'JIN234'were selected as parents to construct the 6th generation group.The isolated population was analyzed by genetic law.The BSA-seq strategy,KASP typing technique and GASP molecular marker were combined to fine mapping the related resistance genes.The developed molecular markers can be used for molecular marker-assisted breeding.The results are as follows:(1)The pathogen of the powdery mildew disease caused by powdery mildew pathogens was identified as Podosphaera xanthii,and the pathogen of the pathogen was identified by the internationally recognized pathogen of the powdery mildew pathogen.The physiological race is 2France·Resistance to 64 Cucurbita pepo L.germplasm resources was identified by using purified powdery mildew pathogens.Among them,13 germplasm resources showed high resistance to the pathogen,and 15 materials showed high sensitivity.In the identified material,the high-resistance material'X10'was selected as the female parent,and the highly susceptible material'JIN234'was used as the male parent for subsequent experiments.(2)Using the disease-resistant inbred line'X10'and the susceptible inbred line'JIN234'as materials,the interaction between the pathogen of powdery mildew and the Cucurbita pepo L.was observed by the brilliance transparent staining method.The susceptible material'JIN234' spores germinated and grew out of the germ tube at 6h after Inoculation.The hyphae of the pathogenic bacteria began to grow for 24h after Inoculation,and the conidial spores of the pathogen began to germinate in 96h after Inoculation;The disease-resistant material'X10'was germinated in the spores of at 48h after inoculation,and the mycelium grew at 120h after inoculation.Compared with the susceptible material'JIN234',,the disease-resistant material'X10'was less in number of germ cells,late in time of occurrence and slower growth of the mycelial when infected by the pathogen.As the germination of the spore bud tube was blocked,the anti-The disease material'X10' showed higher disease resistance.(3)The experiment used the powdery mildew high resistance inbred line'X10'and the susceptible inbred line'JIN234'to prepare the six generations of the parental material for genetic analysis.The resistance phenotype survey was divided into 6 grades(0,1,3,5,7,9),F1 showed resistance(grade 1),F2 population phenotype had disease resistance type(grade 0,1,3),intermediate type(grade 5),susceptible type(grade 7,9),plant resistance ratio For the 3:1,BC1P2 population phenotypes were disease-resistant(grade 1,3),intermediate(grade 5),and susceptible(grade 7,9),and the plant resistance ratio was 1:1.It is indicated that the resistance of Cucurbita pepo L.powdery mildew is controlled by a pair of dominant major genes.(4)The BSA-seq strategy was used to map the disease resistance related genes,and the anti-sensory pool and two parental pools were constructed,and the four pools were re-sequenced.The results of sequencing analyze shows that,the disease resistance gene was mapped on 4.85 Mb range of chromosome 10.In the interval,210 individuals of the F2 population were scanned using the KASP genotyping technique,and the target gene was mapped between the M1940027 and M2716228 marker.The 1300 strains of F2 were scanned by CASP markers to screen the recombinant plants,and the corresponding F2:3 phenotype was used to map the disease resistance genes between PM.C2448658 and PM.C2551764.The distance between markers was 103,106 bp.There are 18 coding genes in the gene.(5)Analysis of 18 gene annotations in the finely mapped segment revealed that three genes had the disease resistance domain RPW8.In this study,the gene expression levels of four genes in the localization interval were analyzed.The trend of Cp4.1LG10g02500 gene irrelevant to disease resistance was not obvious in the 0-48h trend of high-resistance materials and high-sensitivity materials.It is speculated that it is not related to resistant disease.The expression of Cp4.1LG10g02780 gene was increased in 6h-48h after inoculation of high-resistance material.The expression of Cp4.1LG10g02780 gene was down-regulated after inoculation for 6h-48h.The other two genes were low in P1 plants within 0-48h.Based on the expression level of the P2 plant,the Cp4.1LG10g02780 gene was initially identified as a candidate gene for disease resistance.(6)The molecular marker PM.C2448658 was used to screen 2000 F2 populations,and the disease resistance of each individual was identified.The results of field planting phenotype were consistent with the molecular marker screening genotype,which proved that the marker could be used for molecular marker-assisted breeding selection. |
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