Study On Genetic Analysis And Copper Resistance Of Different Germplasm In Melon

In recent years,bacterial fruit spot disease has had a more serious impact on melon production in Xinjiang,and the control of bacterial fruit spot disease mostly relies on copper preparations,which can easily cause copper damage by improper application of copper preparations and affect plant growth and development,and at the same time,copper accumulation can also be harmful to human health.Therefore,it is necessary to screen copper-resistant melon germplasm resources and study the genetic law of copper resistance.The 245 melon germplasm resources were used as experimental materials,and copper preparations were sprayed on melon seedlings to investigate the occurrence of copper damage in the experimental materials,to identify the copper resistance of melon germplasm based on resistance indexes and systematic cluster analysis,and to select copper-resistant parental materials for melon.The copper-susceptible materials of two thick-skinned melons（pure lines of high generation self-crosses）were sprayed with copper preparations at different periods of melon plants to compare the differences in copper susceptibility of melons at different periods;four resistant and susceptible melon materials were selected and configured in two sets of crosses（P_A×P_B,P_C×P_D）for six generations of genetic populations,and their progeny were statistically analyzed for resistance and susceptibility performance.The results of the experiment were as follows.（1）By identifying different melon germplasm resources for copper resistance in the field and evaluating and analyzing melon related resistance indexes,the results showed that 245 melon germplasm resources were classified into four categories,with HR（77）accounting for 31.43%of the total test materials,MR（72）accounting for 29.39%of the total test materials,MS（42）accounting for17.14%of the total test materials,HS（54）accounted for 22.04%of the total test materials.Among them,77 melon germplasm resources,including TM181,TM206,BM195,TM30,BM191,H120,TM21,BM159,TM226 and BM167,had lower incidence and disease index,and the average relative resistance index was higher than 80%.In addition,245 melon germplasm resources were divided into two clusters,A and B,by systematic cluster analysis of the incidence and copper damage index of melon materials,where cluster A included a and b and cluster B included c and d.The clustering results were highly consistent with the results of copper resistance evaluation based on the resistance index.（2）By studying the effects of different copper preparations at different concentrations on the growth of melon,the results showed that the foliar spraying of six copper systems（46%cotrimoxazole3,000 water dispersible granules,99%copper sulfate,99%copper acetate,33.5%quinoline copper suspension,30%copper amberate wettable powder,23%copper turpentine emulsion）at different concentrations on the main vine length,stem thickness,maximum functional leaf area,maximum functional leaf node,maximum functional leaf relative chlorophyll content SPAD value,single melon weight,leaf disease rate and disease index of melon plants.The effects of different copper preparations at 1000 times dilution on growth index and weight of single melon were relatively small,among which46%cortisone 3,000 wettable powder had the least effect,and the leaf disease rate and copper damage index were 9%and 14.83%,respectively.Among the six copper preparations,99%copper acetate was highly susceptible to copper damage on melon plants,followed by 99%copper sulfate,33.5%copper quinoline suspension,30%copper amberate wettable powder,and 23%copper pine tar emulsion.Among the six copper preparations,99%copper acetate was very susceptible to copper damage to melon plants,99%copper sulfate was second,33.5%copper quinoline suspension,30%copper amberate wettable powder,23%copper pine tar emulsion and 46%cortisone 3,000 water dispersible granules were relatively safe for melon.（3）The effects of copper treatments on vine length,stem thickness,maximum functional leaf area,maximum functional leaf node,maximum functional relative chlorophyll content SPAD value,single melon weight,central sugar content,leaf disease rate and copper damage index were investigated at different periods（pre-sowing dip,seedling stage,vine extension stage and melon setting stage）,and the results showed that copper treatments at different periods reduced the vine length,stem thickness,maximum functional leaf area,relative chlorophyll content SPAD value,yield and quality of both melon materials to different degrees.M625 and M44 were the most sensitive to copper preparations at the seedling stage,with the most severe copper damage,followed by the second most severe at the melon stage.The difference between the preemergence treatment and CK was not significant,and M625 was more sensitive to copper preparation compared with M44.The differences in the effects of copper preparations on the growth,yield,quality and copper damage indexes of the two melon materials at different periods were basically the same,with the order of copper sensitivity being seedling stage>melon sitting stage>vine extension stage>pre-sowing stage.（4）Statistical analysis of resistance and susceptibility of the progeny of the six-generation genetic population of the two sets of cross combinations showed that the separation ratios of resistance and susceptibility of the progeny of the six-generation genetic population of the two sets of cross combinations were in accordance with the Mendelian inheritance law,and in the 2 sets of cross combinations,the separation ratios of susceptibility and resistance of F₂plants were in accordance with the Mendelian 3:1 inheritance law by chi-square test,and the separation ratios of the F₁and parent backcross progeny were in accordance with the Mendelian 1:1 inheritance law by chi-square test.