Research On Disease Resistance Mechanism Of Postharvest Infecting Alternaria Alternata And Salicylic Acid Treatment To Melon

Melon is one of the most famous fruit in Xinjiang.However,it is easily infected by pathogenic microorganism in the postharvest,ablity of disease resistance reduce during the storage and goes to rot finally,causing great economic losses each year,seriously affect the sustain and stable industry development of melon in Xinjiang.Jiashi melon and 86-1 melon are used as test materials in this paper.Good preservation mechanism of Jiashi melon through analysising differenence of melon against A.alternata was discussed.Provide theoretical basis for the research and development for controlling disease of melon and preservation technology in the postharvest,as well as breeding for improving disease resistantance of melon.The research contents are as follows:?1?Jiashi melon and 86-1 melon were inoculated with A.alternata,the materials were transferred to cold storage at 6-8 degree,phenylpropanoid pathway in muskmelon fruit was investigated.The results showed that the incidence of disease and the lesion diameter of fruit inoculated were lower than that of 86-1 melon.Enzyme activity was significantly higher than86-1 melon.These findings suggested that phenylpropanoid pathway played a positive role at early stages of A.alternata muskmelon interaction,however,the resistance role of phenylpropanoid metabolism decreased with the expansion of dry rot.The activities of phenylpropanoid pathway Jiashi melom were significantly higher than in the 86-1 melon.Jiashi melon fruit has a stronger resistance to A.alternata infection.?2?Using Jiashi melon and 86-1 melon cDNA as a template and cloned GLU?PAL genes sequence.Sequence length of GLU are 2055 bp,encoded 684 amino acids,the complete open reading frame,there is signal peptide MEETCKQSPFSILFFFLLLTAAPVSA,contain Glyco_hydro₈1 super family type conserved domain;sequence length of PAL are 928 bp,encoded 294 amino acids,had the complete open reading frame,no signal peptide,Secondarystructure PAL genes are in composition prediction alpha helix,random coil-based,extension chain,beta fold.The phylogenetic tree showed that the PAL amino acid sequence of the amino acid sequence was the highest.?3?Jiashi melon and 86-1 melon were inoculated with A.alternata,the materials were transferred to cold storage at 6-8 degree,determination of lesion size,the activities of CHT,GLU and the gene expression rules for CHT and GLU.The results showed that the incidence and the lesion size of Jiashi melon were lower than that of 86-1 melon during the inoculated with A.alternata after 15 days.During the infection period,the activities of CHT,GLU was significantly increased with a trend from rise to decline.The activities of CHT,GLU in Jiashi melon significantly higher than 86-1 melon.Jiashi melon to resist the infection of A.alternata by enhancing the activity of protease and maintaining the enzyme activity at a higher level;The relative expressions for CHT1,CHT2,GLU1 were higher in Jiashi melon than 86-1 melon during the whole infection period.These results suggest that the pathogenesis related proteins play a key role in the early and middle stage of plant pathogen resistance.?4?To research the effect of postharvest salicylic acid dipping on A.alternata of Jiashi melon and 86-1 melon.Muskmelon fruit were dipped at 3 mmol/L,6 mmol/L,9 mmol/L SA of 10 min,inoculated with A.alternata.Placing at 6-8 degree,relative humidity 85%-90%,of the refrigerator for storage.Apricot fruit soaked in distilled water were used as a blank.The results indicated that: Salicylic acid treatment increased the activities of PAL,SOD,CAT,POD,GLU,CHT.After a treatment of SA,the Muskmelon has a significantly enhanced disease resistance to pathogens.3 mmol/L SA treatment can significantly improve the disease resistance of Jiashi melon fruit during storage.6 mmol/L SA treatment can significantly improve the disease resistance of 86-1 melon fruit during storage.