Isolation And Identification Of Phytophthora Pathogens And Screening Of Resistant Germplasm Resources In Pumpkin

Pumpkin is an important horticultural crop,which has a long planting history and a wide cultivation area in China.With the continuous expansion of pumpkin planting area,the occurrence of Phytophthora blight is becoming more and more frequent,especially in the northeast production area of seed-used pumpkin.Phytophthora blight has caused serious economic losses to biology and agriculture and becoming one of the main obstacles to the development of pumpkin planting industry.The impact of Phytophthora blight can be reduced to a certain extent through chemical,biological,agricultural and other control measures,but these methods can not fundamentally solve the problem,and even caused environment damage.Breeding of resistant varieties is an economical,effective and environmentally friendly control method,and screening of resistant germplasm resources is the basis of this work.Therefore,this study started with the pathogen identification of pumpkin Phytophthora blight.First,the pathogen of pumpkin Phytophthora blight were identified by morphological and molecular biological methods,and then a simple and effective methods for identifying resistant resources was constructed.Based on it,the resistance of 99 pumpkin germplasm resources was screened.The results are as follows:1.Five strains were isolated from pumpkin fruits naturally infected with Phytophthora blight,and morphological and molecular biological identification were performed.The pathogen of Pumpkin Phytophthora blight was identified as Phytophthora capsici.Result of pathogenicity test showed that all the five strains of Phytophthora capsici had pathogenicity,and there were obvious differences in the pathogenicity among the five strains.2.The effects of different factors on the severity of Phytophthora blight was researched with orthogonal experimental design method,and the resistance identification of pumpkin Phytophthora blight was established.The inoculation method was root irrigation at 1-2-leaf seedling plant stage with density of 1×10~6/m L,at 20-25℃and 90-100%humidity condition.3.According to the established identification method of pumpkin disease resistance,99 pumpkin germplasm resources were identified,and 6 resistant materials were selected,accounting for 6%of the test materials,which were Indian pumpkin D7-14,D17-20,D18-15,R119,D15-3,D13-9.There were55 susceptible materials,accounting for 56%of the tested materials.There were 38 highly susceptible materials,accounting for 38%of the tested materials.4.28 germplasm resources were identified with inoculation of isolated leaves and root irrigation inoculation methods,and the correlation between disease index of the two inoculation methods was analyzed.The results showed that the correlation coefficient between the disease index of detached leaf inoculation and seedling root inoculation was 0.656,reaching a very significant positive correlation.The two inoculation methods were used for screening of resistant germplasm resources in pumpkin.Compared with the root irrigation inoculation method,the inoculation of isolated leaves was easy to control the experimental conditions,easy operation,and had fast and accurate identification results.Therefore,the inoculation of isolated leaves method could be used for resistance screening of a large number of germplasm resources in pumpkin.