Leaf Structure Difference Analysis Of Different Powdery Mildew Resistance Of Seed-used Pumpkins And Evaluation Of Combining Ability Of Seed-used Pumpkin Inbred Lines(Cucurbita Pepo L.)

With the high-generation inbred lines of seed-used pumpkin and powdery mildew pathogen as materials,13 internationally accepted melon physiological race identification hosts and standard systems were used to identify the powdery mildew physiological races in Hohhot,Inner Mongolia in 2020.The pathogenicity of powdery mildew pathogen to pumpkin inbred lines in two years was determined by artificial inoculation,and the correlation between leaf structure and powdery mildew resistance was analyzed.At the same time,the combining ability,heterosis and heritability of pumpkin materials were analyzed by incomplete diallel cross design,which provided a theoretical basis for the hybrid breeding of seed pumpkin powdery mildew control in the future.The main research results are as follows:1.The physiological races of Inner Mongolia in 2020 were identified as 2US,compared with 2019,the pathogenicity of physiological races changed,and significantly improved.2.The results of leaf structure study showed that the resistance of pumpkin leaves to powdery mildew was positively correlated with wax content,negatively correlated with stomatal density,and had no correlation with villus density.The epidermal cell length and the ratio of palisade tissue to spongy tissue of resistant leaves were significantly higher than those of susceptible leaves.After inoculation,the number of layers of cells in each tissue increased,and the large cells became multiple small cells,which changed from long to round,and the change of susceptible materials was more intense.3.The comprehensive evaluation of the general combining ability of parent H was relatively high,and C×E was the best combination for single melon yield and grain traits;A×D is the best combination of quality traits.4.Cluster analysis is used to divide all parents into three categories,among which parents A,B and C are the first category,parents E and E are the second category,and parents D,H and G are the third category.5.The 15 selected combinations showed uniform positive super-parent heterosis in single fruit seed yield and crude fat traits,and negative super-middle or super-parent heterosis in longitudinal diameter.