Study On Control Of Alternaria Toxins In Jujube Based On Biological Inducer And Fungicides

With the rapid development of the jujube industry in Xinjiang,black spot disease has caused a decrease in jujube yield,deterioration in quality,and serious economic losses,while the toxins produced by black spot disease pose a threat to the health of humans,animals,and the environment.In this study,dates from Alal jujube orchards were used as test materials for the treatment of Streptomyces spp.with bioinducers 5000 μM salicylic acid(SA)and 100μM methyl jasmonate(Me JA),and biogenic fungicides 25 μM Trichoderma harzianum Selenium nanoparticle(TSNP)as the test agent and 200 μM Tebuconazole(WZ)as the control chemical fungicide were sprayed in the field,and the dates were inoculated with Alternaria alternata(A.alternata)at the full red stage(in the field)and at the harvest and storage stage(in vitro).We collected samples at different days after inoculation and investigated the effects of different treatments on the virulence production and virulence gene expression,disease resistance related enzyme activity and enzyme gene expression,and the evaluation of nutritional quality of jujube at maturity,and explored the growth and virulence production mechanism of different bioinducers and fungicides on Streptomyces jujube in the field and in vitro experiments.The results were as follows:(1)The effects of different treatments on nutritional quality,Me JA and TSNP treatments reduced the reducing sugar content of jujube by 3.38% and 12.51%,respectively;SA and WZ increased the fructose and glucose content by 16.73%,5.55% and 18.23%,19.37%,respectively;WZ reduced the protein and amino acid content of jujube by 12.09% and 8.80%,respectively.(2)In the field and in vitro experiments,the toxicity production of the streptogram toxins alternariol(AOH),alternariol monomethyl ether(AME)and tenuazonic acid(Te A)was basically the same,with the highest level of Te A in the CK group,reaching 1239.79 μg/kg in the field test and 50653.22 μg/kg in the in vitro experiment.In the field test,Me JA and TSNP treatments were the most effective in inhibiting the synthesis of AOH and AME,with 47.72%-63.01% reduction compared to CK,while SA treatment and WZ control were the most effective in inhibiting the synthesis of Te A,with 96.89% and 98.89% reduction compared to CK,respectively.The best effect of SA and Me JA treatment on the inhibition of toxinproducing genes mot I and aom R was reduced by 3.77～13.09 times compared with CK,and the best effect of Me JA and TSNP treatment on the inhibition of toxin-producing genes pks A and pks J was reduced by 2.25～9.81 times compared with CK.In the in vitro experiment,SA and TSNP treatments had the best inhibitory effect on AOH and AME synthesis,with89.97%～95.79% reduction compared with CK;SA treatment and WZ control had the best inhibitory effect on Te A synthesis,with 86.41% and 99.28% reduction compared with CK.SA and TSNP treatments had the best inhibitory effect on toxin-producing genes omt I,aoh R,pks A and pks J gene expression were best suppressed by SA and TSNP treatments,with23.8～43.4-fold and 14.5～18.6-fold reductions,respectively,compared with CK.(3)The different treatments increased the activity of disease-resistance-related enzymes(Peroxidase(POD),polyphenol oxidase(PPO),Superoxide dismutase(SOD),Catalase(CAT),Ascorbate peroxidase(APX),Phenylalamine ammonialyase(PAL))to varying degrees in both field and in vitro experiments.),Ascorbate peroxidase(APX),and Phenylalamine ammonialyase(PAL)activities,and up-regulated the expression of disease-resistance-related enzymes(POD,PPO,SOD,CAT,APX,and PAL)genes,thereby increasing the resistance of jujube fruits to The pathogen resistance of jujube fruits was improved.In field experiments,the different treatments increased the activity of disease-resistance-related enzymes by1.1～14.0-fold and up-regulated the expression of disease-resistance-related enzyme genes by1.3～1.8-fold compared with CK;in in vitro experiments,the different treatments increased the activity of disease-resistance-related enzymes by 1.2～2.2-fold and up-regulated the expression of disease-resistance-related enzyme genes by 1.3～3.9-fold compared with CK.In conclusion,preharvest spray treatment with different bioinducers and fungicides is not only a safe and effective way to control streptavidin in red dates,but also as an effective measure to preserve the freshness of fruits and vegetables.