| Melon(Cucumis melo L.)was infected by Gummy stem blight(GSB)during growth period,and GSB was one of disease in melon production.The most economical and effective control method was GSB resistance breeding of melon.The main method was resistance identification screening resistant materials at present,the less study on selection and identification on aspects of expression levels of defense related genes and morphological structure.In my study,the expression levels of defense related genes and morphology structure in different melon genotypes resistance to GSB were compared and analyzed,and study on the relationship between melon genotypes resistance to GSB and the expression levels of defense related genes and morphological structure.Providing the theoretical basis for a further study on melon GSB resistance mechanism.1.Relationship between difference of resistant among melon genotypes resistance to Gummy stem blight and leaf morphology structureIn order to investigate the relationship of disease index and leaf structure,stomata,pubescence and wax content in eight different resistant melon genotypes resistance to gummy stem blight(GSB),including four melon genotypes high resistance to GSB,three melon genotypes resistance to GSB and melon genotype susceptible to GSB by paraffin section,epidermal tearing,collodion methods.The results showed that the correlation coefficient between leaves back of stomatal density,pubescence density,thickness of spongy tissue,structure porosity and structure compactness and disease index was r = 0.86264>0.8,r = 0.97672>0.8,r = 0.85612>0.8,r = 0.90701>0.8respectively,it meant that the ability of resistance to GSB in melon materials had a significantly positive correlation to leaf back of stomatal density,pubescence density,thickness of spongy tissue and structure compactness,namely the lower of leaf back of stomatal density,pubescence density,thickness of spongy tissue and structure compactness of melon resistant genotypes.The correlation coefficient between leaf wax content and thickness of lower epidermis and disease index was r =-0.92240>-0.8,r =-0.92064>-0.8 respectively,it meant that the ability of resistance to GSB in melon genotypes had a significantly negative correlation to leaf wax content,thickness of lower epidermis,namely the higher of leaf wax content and thickness of lower epidermis in resistant genotypes.Under fluorescence microscope to investigating the defense reaction of melon leaf after point inoculating GSB race A1 by utilization of aniline blue fluorescence staining method to stained the infected melon leaves,including high resistance to GSB 145-471 and susceptible to GSB baipicui.The results showed that callose deposition in and around the epidermal cell of melon leaf.It meant that callose deposition in infected epidermal cells wall when the GSB pathogen infected melon leaves.2.Relationship between difference of resistant among melon materials resistance to Gummy stem blight and expression patterns of defense related genesIn my study,In order to analyze for the transcript levels of six defense related genes among the high resistant genotypes 145-471 and 082-398,resistant genotype 145-082 and susceptible genotype baipicui after inoculating GSB race Al,including pathogenesis-related protein(PR)-1 gene,-3 gene,-9 gene,lipoxygenase 2 gene,super-oxide dismutase gene and ascorbate peroxidase gene.The results showed that:the expression patterns of the six defense related genes were achieved the maximum in high resistant genotype 145-471,and the expression patterns of pathogenesis-related(PR)-1 gene,-9 gene,lipoxygenase 2 gene and superoxide dismutase gene in resistant genotypes are higher than the expression of those genes in susceptible genotype.The early expression levels of PR-1 gene,PR-3 gene in melon genotypes resistance to GSB,and compared with melon genotype susceptible to GSB,increased expression of PR-1 gene,PR-3 gene after inoculation 24h,12h respectively.At the seven time point in 0-72h,the expression patterns of PR-9 gene,LOX-2 gene,SOD gene and APX gene of melon genotypes resistance to GSB were higher than those genes in susceptible genotype,and the maximum expression patterns of PR-9 gene,LOX-2 gene,SOD gene and APX gene in 145-471 genotype high resistance to GSB were approximately 11.81 times,5.78 times,3.43 times and 11.84 times of those genes in susceptible genotype respectively.At the most inoculation time points,the expression patterns of pathogenesis-related(PR)-1 gene and Ascorbate Peroxidase gene in resistant genotypes were higher than those genes in susceptible genotype.In addition to pathogenesis-related(PR)-1 gene,the rest of five defense related genes in high resistant genotypes 145-471 and 082-398 had higher expression pattern than those genes in resistant genotype 145-082.This study indicated that:the resistance degree of plant resistance to given pathogen were more related to reaction time and expression magnitude of defense related genes than various defense related genes. |
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