Identification And Evaluation Of Resistance To Downy Mildew In Grape Varieties

In this study,105 grape varieties were used as test materials,and the resistance to downy mildew was identified by indoor in vitro leaf inoculation method.The dynamic changes of physiological and biochemical indexes and microscopic section observation were carried out on some varieties after inoculation.At the same time,real-time quantitative PCR(q RT-PCR)was used to analyze the relative expression of grape downy mildew resistance gene in disease-resistant and susceptible varieties.The main results are as follows:1.In this study,105 grape varieties were used as test materials,and the resistance and identification of grape downy mildew were carried out by indoor in vitro leaf inoculation method.The results showed that different grape varieties had different resistance to downy mildew.Among the 105 grape resources,susceptible and high-sensitivity individuals are mostly V.vinifera L.species,15 V.vinifera L.×V.labrusca L.are resistant to downy mildew,and only 9 V.vinifera L.resources are expressed as medium-resistant,’V.riparia Michx..And the V.rupestris Scheele are resistant to disease and high resistance.This study screened out 10 varieties of high-resistance downy mildew,namely: V.riparia Michx.No.1,V.riparia Michx.No.6,V.riparia Michx.No.7,’Freedom’,’SO4’,V.riparia Michx.No.5,V.riparia Michx.No.8,Shuang qing,Zuoshanyi,’Concord’.2.After inoculation of grape downy mildew on different varieties of resources,the activities of two enzymes PPO and POD were studied.The results showed that the enzyme activity of resistant varieties increased significantly at 1 d,while the enzyme activity of susceptible varieties did not change or decreased.At the 5th and 7th days later,most of the susceptible varieties showed PPO,and the POD enzyme activity increased.In the auxiliary identification of downy mildew resistance,it can be seen that the disease index after grape inoculation of downy mildew has a significant correlation with POD,PPO activity and stomatal density before inoculation on the 1st day after inoculation,which is negatively correlated.POD,PPO activity and stomatal density of grape leaves after inoculation of downy mildew on 1 d may be an auxiliary method for identification of grape downy mildew resistance.3.After inoculation of downy mildew,the PR1 gene has a high expression level in’Bronx Seedless’,’V.riparia Michx No.7’ and ’Double Red’,and the highest is 2000 times of the ’Canadice Seedless’ period.The highest expression level of the PR1 gene in the susceptible and medium resistant varieties was less than 600 times that of the ’Canadice Seedless’ period.However,the correlation between gene NPR1 and gene PAL expression was significant,and the same trend was observed in the same variety.The three disease resistance genes had peak expression levels during the same period.