Resistance Of Different Strawberry Varieties To Powdery Mildew And Gray Mold And Tissue And Physiology Characteristics

The yield and quality of strawberries can be affected seriously by powdery mildewand gray mold.The long-term use of chemical pesticides can lead to many problems,such as the reduced susceptibility of pathogens to pesticides,lower control effect,and higher residue and more serious environmental pollution.Screening and promoting resistant strawberry varieties is one of the important measures to control powdery mildew and gray mold.There is a lack of strawberry germplasm resources resistant to powdery mildew and gray mold in China,and there are relatively few studies on screening strawberry resistant varieties and its resistance mechanisms.Therefore,screening strawberry resistant varieties and studying the resistance mechanism has an important significance for the sustainable development of strawberry.In this study,the resistance of 29 different strawberry varieties to powdery mildew and gray mold was determined by indoor and field experiments.The upper and lower epidermis and palisade tissues of high resistant,middle resistant,middle susceptible and high susceptible species were observed using paraffin section technology.The structure of sponge and spongy tissue was used to determine the physiological indexes of chlorophyll,total phenols,flavonoids and soluble protein content in different resistant strawberry varieties by spectrophotometry.The relationships between tissue structure,physiological indexes and disease resistance with resistance were analyzed.The main results are as follows:1.From 29 strawberry varieties,6,15,6 and 2 varieties were identified to high resistant,middle resistant,middle susceptible and high susceptible to powdery mildew,with the representative varieties of Meiho,All Star,Shiberry No.2 and Red Pearl,respectively.Meanwhile,5,14,6 and 4 varieties were identified to high resistant,middle resistant,middle susceptible and high susceptible of gray mold,with the representative varieties of Shuofeng,Akihime,Dana and Mei Xiangsha,respectively.The resistant varieties to powdery mildew and gray mold were Sweet Charlie and Meiho.But,the susceptible variety to powdery mildew and gray mold was only Red Pearl.2.There were some differences between the growth indicators of the different varieties in field experiment,such as high resistant varieties to powdery mildew and gray mold including Meiho,Sweet Charlie and Shuofeng,and high susceptible varieties,such as root number,stem diameter,fresh dry weight above ground,and fresh dry weight of roots,but with no relation to the resistance.At the harvest stage,the occurrence of powdery mildew and gray mold disease of Meiho,Sweet Charlie,and Shuofeng were all lower than 15.The disease index of powdery mildew and gray mold were all above 30,andwere all significantly higher than those of other varieties.The above results were consistent with the results of indoor identification.3.The epidermis and palisade tissues of the resistant strawberry varieties were arranged neatly,tightly and regularly,while the epidermis cells of susceptible strawberry varieties were arranged loosely,irregularly with multiple voids.There was a significant negative correlation between the disease index and leaf thickness,palisade tissue thickness and compactness of leaf structure,respectively,but there was a significant positive correlation with sponge tissue thickness,structural porosity,and stomatal density,respectively.4.After 10 days of inoculation with Sphaerotheca aphanis,the chlorophyll content of resistant varieties,Meiho and Sweet Charlie,decreased by 9.6% and 12.5%,respectively,which were significantly lower than those of high sensitive varieties,Toyonoka and Red Pearl.The total phenol content flavonoids increased by 202.5% and 171.3%,respectively,and the content of flavonoids increased by 34.1% and 44.3%,respectively,while the total phenol content of Toyonoka and Red Pearl increased by 86.5% and 73.6%,respectively,and the content of flavonoids increased by 17.9% and28.7%,respectively.The increase was significantly higher than that of resistant varieties.The soluble protein content showed a downward trend with the increasing days of inoculation,while Meiho and Sweet Charlie increased significantly,and both were significantly higher than those high-inductance varieties.There was no relationship between the leaf water content and the resistance in resistant and susceptible varieties.5.After 10 days of inoculation with Botrytis cinerea,the chlorophyll content of the resistant varieties Shuofeng and Sweet Charlie decreased by 7.1% and 11.5%,respectively,which were significantly lower than those of the susceptible varieties Red Pearl and Meixiangsha.Compared to the pre-infection,the content of total phenols increased by 175.6% and 168.3% with the increase by33.3% and 42.7% in flavonoid content,by 65.4% and 67.6% in total phenolic content and by 17.4% and19.7% in flavonoid content,respectively.,where the increase was significantly higher than those of resistant varieties.With the extension of inoculation time,,the soluble protein content of the resistant varieties showed a downward trend,while the susceptible varieties showed an upward trend.There was no relationship between in the resistant and susceptible varieties in leaf water content.