| The application of chemical fungicides is one of the most important ways to the storage and preservation of fruits after harvest.However,the use of chemical fungicides will lead to pesticide residues in fruits,threatening fruit safety and human health.Bamboo vinegar(BV)is a natural plant liquid,which possess a positive application prospect in fruit disease control and storage.In this thesis,BV and three fungicides pyraclostrobin(Py),thiophanate-methyl(Th),tebuconazole(Te)are selected as raw materials.The aims are: to prepare four kinds of bamboo vinegar mixtures;to explore the dissipation dynamics of chemical fungicides in the bamboo vinegar mixtures in pear under different storage conditions;to determine the storage preservative effect of the four mixtures on pears under different application methods;and preliminarily reveal the preservative mechanism using transcriptomic sequencing technique.The results of this study will provide basic data for the development and application of BVbased storage fresh-keeping compounds,which is of great significance for reducing the use of chemical storage fresh-keeping agent and ensuring fruit safety and human health.The main research results are as follows:(1)A total of four kinds of preservative and fresh-keeping mixtures were prepared.They were 77.3% Py·Te·BV water emulsion(w.e.),92.8% Th·Te·BV suspension concentrate(s.c.),93.0% Py·Th·BV suspension concentrate(s.c.),and 93.0% Te·Th·BV suspension concentrate(s.c.),respectively.The control indexes of thermal storage stability,p H value,suspension rate,and lasting foaming property all met the national standards.(2)The dissipation dynamics of fungicides in the four mixtures in pears were clarified under normal room temperature and refrigeration conditions.The dissipation of Th,Te,and Py in pears followed the first-order kinetic equation under both two conditions,with the dissipation half-lives of 3-47,14-32 and 11-33 d(room temperature)and 37-67,75-187 and70-144 d(refrigerated),respectively.The initial residues of Th,Te,and Py were 0.13-0.31,0.08-0.20 and 0.11-0.24 mg/kg in the mixtures,respectively,while those in the commercial fungicides were 0.59-1.05,0.57-0.77 and 0.58-1.47 mg/kg,respectively.The initial residues of the three chemical fungicides in the mixtures was much lower than the commercial fungicides and the maximum residue limit.(3)The weight loss rate,rot rate,hardness number,titrable acid,soluble solid,respiratory rate and Vitamin C were measured.The preservation effects of BV mixtures on pears were investigated under two different application methods.After spraying with BV mixtures,the weight loss rates and bad fruit rates of pears were 4.32%-5.70% and 16.67%-38.33% at normal temperature for 30 d,respectively;and the weight loss rates and bad fruit rates of pears were 3.01%-3.95% and 1.67%-8.33% under refrigeration for 90 d,respectively.After soaking with BV mixtures,the weight loss rates and bad fruit rates of pears were 3.83%-5.32% and 15.00%-41.67% at normal temperature for 30 d,respectively;and the weight loss rates and bad fruit rates of pears were 3.11%-4.01% and 1.67%-8.33% under refrigeration for 90 d,respectively.The preservation effect of the four BV mixtures was better than that of commercial chemical fungicides.Among which,93.0% Py·Th·BV s.c.possessed the best preservation effect.(4)Transcriptomic sequencing technique was used to reveal the storage and preservation mechanism of 93.0% Py·Th·BV s.c.A total of 1450 differentially expressed genes were identified after treatment with 93.0% Py·Th·BV s.c.KEGG pathway analysis showed that the aforementioned differentially expressed genes were mainly enriched in the plant hormone signal transduction pathway.In which the expression of ethylene receptor ETR and EBF protein genes and the regulatory gene NPR1 in salicylic acid signal were significantly up-regulated after the application of the mixture,which may be involved in the delaying of the ripening and senility and enhancement in disease resistance of pear fruit. |
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