Screening,identification Of Antagonistic Yeast And Effect Of Its Biocontrol Agents On Postharvest Loquat During Storage

Loquat(Eriobotrya japonica Lindl)is one of characteristic fruit in Southeast China, loquat easily decay postharvest and is not easy to storage. Antagonistic yeast has been proven can effectly inhibite the disease caused by pathogens on postharvest fruits. This paper is mainly about screening of antagonistic yeast that significantly against pathogen which causes loquat anthracnose, and about exploring the biocontrol mechanism of antagonistic yeast, and made the antagonistic yeast into liquid dosage forms and solid dosage forms and applied of preservation of loquat, study the effects of these two forms in loquat fruit during storage.The main contents and results of the research are as follows:(1) Screening of antagonistic yeast from loquat fruit surface that are not injured or decayed, the method of two-step screening and in vivo screening are used to obtain an antagonistic yeast named Y35-1, yeast Y35-1 can be effectively suppress loquat anthracnose caused by Colletotrichum gloeosporioides; through the tests of morphological characteristics, physiological and biochemical characteristics, molecular characteristics, according to the identification results, yeast Y35-1 is identified as Pichia guilliermondii.(2) According to the results of in vitro test on PDA plates and in vivo testing of loquat fruit, the best effect of suppressing concentration of yeast Y35-1 is 1×108cfu/ml; the study find yeast Y35-1 can be capable of inhibiting pathogenic fungi spore germination; Under an optical microscope, yeast Y35-1 can be attached to the pathogenic fungal hyphae and inhibited the growth of pathogenic fungal hyphae; yeast Y35-1 is able to secret antimicrobial substances, so pathogenic fungal hyphae present similar dissolved state, also can produce volatile antimicrobial substances to inhibit pathogenic fungal hyphae expansion and growth.(3) This paper also study the method of yeast Y35-1 loquid dosage forms and active freeze-dry powder, by measuring its viability and effectiveness of biocontrol yeast cell during storage, evaluating the feasibility of the method and biocontrol agents; the results show that biocontrol agents made by the methods can apply to aspects of loquat fruit postharvest disease control, both show the methods of preparation is valid; And 4℃ is the most suitable for storage for yeast Y35-1 liquid formulation,-20℃ is the most suitable for storage for yeast Y35-1 activity freeze-dry powder; To maintain the viability and biocontrol effect of yeast Y35-1 during storage, trehalose has played a positive role in protection.(4) The selection of these two biocontrol agents are used to soak treatment loquat fruit, studying the effects of these two biocontrol agents in terms of loquat storage, the result show: these two biocontrol agents can effectively inhibit decay incidence of loquat fruit during storage, when the 25 th day in the storage, decay index is only 3.89% and 4.06%, respectively. And these two biocontrol agents on the loquat weight loss, firmness, soluble solids, skin cell membrane permeability, vitamin C content, total sugar content, total acid cintent, POD activity and SOD activity played a certain respects positive effects. These two biocontrol agents exist a positive impact on aspects of loquat postharvest storage, and are worth to further research and spread.