Pathogen Identification Of Pumpkin Anthracnose And Evaluation Resistance Of Germplasm Resources

Pumpkin,an important vegetable crop,is an annual herbaceous plant belonging to Cucurbita which is a genus in the gourd family Cucurbitaceae.Pumpkins are highly adaptable and have high nutritional and medicinal values.Therefore,it has a wide cultivation area worldwide.Anthracnose is one of the main diseases in pumpkin production.The yield and quality of pumpkin can be seriously reduced by its presence in all growth stages.At present,research on pumpkin anthracnose mainly focuses on comprehensive prevention and control.The fundamental solution is breeding resistant varieties,and screening and identification of resistance to anthracnose in pumpkin germplasm resources are particularly important.In this study,we isolated and purified pumpkin anthracnose from Xiangyang Base of Northeast Agricultural University in Heilongjiang Province.Based on morphological characteristics and molecular biology,the pathogen was identified and biological characteristics of pathogen were analyzed.A set of method for identifying resistance to anthracnose was constructed,and the resistance screening of pumpkin germplasm resources was carried out.The results are as follows:1.In this study,three pathogen strains were isolated from pumpkin fruits naturally infected with anthracnose,and were named as TZ0,TZ02,and TZ15,respectively.Through morphological and molecular identification,the pathogen of pumpkin anthracnose was identified as Colletotrichum magnum.The results of pathogenicity test showed that all the three strains had pathogenicity,and there were significant differences in pathogenicity among the three pathogen strains.Among them,the most pathogenic strain was TZ02,and it was used for the future study.2.The pathogenic biological characteristics of pumpkin anthracnose were studied.The results showed that the optimum growth conditions of mycelium were in a dark culture environment at 28℃.The optimum initial pH was 6,the optimal carbon source was soluble starch and the best nitrogen source was peptone.The lethal conditions of pathogen were 55℃for 10minutes.3.Through in vitro leaves inoculation and spray inoculation at seedling stage methods,42pumpkin germplasm resources were identified for the resistance to anthracnose pathogen.7materials showed moderate resistance（MR）to anthracnose by in vitro leaf inoculation method.1material was high resistance（R）and 9 materials were moderate resistance（MR）to anthracnose by spray inoculation at seedling stage method.Correlation analysis of identification results using the two methods was performed,and the results showed that there was a positive correlation between disease index of the two methods,and the correlation coefficient was 0.643.4.The influence of pathogen concentration,seedling age,temperature and humidity on pumpkin anthracnose infection was analyzed using L₉（3⁴）orthogonal experimental design method.A set of method for identifying resistance to anthracnose was preliminarily constructed.The inoculation method was spray inoculation method at 2-leaf seedling stage with density of 1×10⁷/m L,at 25-30℃and 90-100%humidity condition.5.A total of 113 germplasm resources were screened for resistance to anthracnose using the above established method,and 3 high resistance resources（R）and 19 moderately resistance resources（MR）.