Transcriptome Analysis And Disease-resistant Germplasm Identification Of Summer Squash In Response To Powdery Mildew Infection

Zucchini(Cucurbita pepo L.)is an annual herb of the Cucurbitaceae Cucurbita genus,and it is also an important vegetable crop of the Cucurbita genus.In recent years,as the planting area and output of zucchini in my country have increased year by year,it has greatly increased the income of farmers and also has great significance for the adjustment of agricultural structure.Powdery mildew is the main fungal disease that affects the yield loss of summer squash.It has a wide range of distribution and has gradually become an important factor limiting the yield of summer squash.Therefore,analyzing the regulation of summer squash in response to powdery mildew infection will make it have important theoretical and application value in the production of summer squash.In this study,the zucchini inbred lines with high resistance and high susceptibility to powdery mildew were used as materials.By inoculating them with powdery mildew bacteria,the physiological and biochemical response characteristics of summer squash after powdery mildew infection were first analyzed,and then the transcriptome was used to participate in the analysis.The related genes of summer squash in response to powdery mildew infection were systematically identified,and finally the main domestic summer squash varieties were systematically evaluated and screened for resistance to obtain powdery mildew-resistant germplasm.This study provides an effective basis for zucchini disease resistance breeding and the mining of important disease resistance candidate genes,and provides usable germplasm materials for zucchini resistance to powdery mildew breeding.The main findings are as follows:(1)Perform superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),and phenylpropanase on zucchini leaves 0 h,12 h,24 h,and 48 h after powdery mildew inoculation.Determination of the activity of acid ammonia lyase(PAL)and the content of malondialdehyde(MDA),protein quantification,these physiological and biochemical indicators,analysis of the physiological change trend of zucchini in response to powdery mildew infection,within 48 hours after inoculation with powdery mildew,SOD activity,POD activity and CAT activity gradually increase with the increase of time,and disease-resistant materials are higher than those of susceptible materials,indicating that the resistance of zucchini to powdery mildew is related to the activities of these three enzymes;PAL activity value sense The change of diseaseresistant materials is not obvious,while the PAL activity value of disease-resistant materials shows a trend of first decline,then increase,and finally decline again.The range of changes is large,but the PAL value of disease-resistant materials is much larger than that of disease-resistant materials,indicating that PAL activity will not directly affect Powdery mildew has an effect,but it still plays an important role in the physiology of powdery mildew resistance;the MDA value first rises and then decreases,and the disease-susceptible materials are higher than the disease-resistant materials,which further shows that the MDA content and zucchini powder There is a certain correlation between disease resistance.(2)Transcriptome sequencing analysis of susceptible and resistant zucchini leaves at 0 h and 24 h after powdery mildew inoculation,1442 differentially expressed genes were identified in susceptible materials,and 3,510 differentially expressed genes were identified in resistant materials.Based on enrichment analysis of differentially expressed genes,genes that control phytohormone signal transduction and plant pathogen interactions were significantly up-regulated in disease-resistant materials,and genes that control phytohormone signal transduction and circadian rhythm changes in plants were significantly up-regulated in disease-resistant materials.,Indicating that these genes may be highly related to the resistance to powdery mildew of zucchini;analysis of the differentially expressed genes involved in hormone transmission shows that there are a total of 56 genes that express the hormone transmission of diseased materials,of which 32 genes Up-regulated expression;a total of 125 genes are expressed through hormone transmission in anti-disease materials,of which 76 genes are up-regulated.(3)Using the indoor seedling stage artificial inoculation spray method,the resistance level of 58 zucchini varieties to powdery mildew was systematically identified.11 disease-resistant varieties were identified by the comprehensive disease index method and cluster analysis method of resistance evaluation methods,respectively: ’Heatwave’,’Green Beauty’,’Xia Li’,’French Green Bei 9810’,’Excellent’,’Wansheng Jiaozi’,’Lilang No.3’,’Xiyu’,’Chaoyan No.4’,’Jinghu 42’,’Cuihu 336’.