Studies On The Application And Antagonistic Mechanism Of Biocontrol Medicament In The Storage Of Grapes

Postharvest dieases of grapes have lead huge losses. Anciently, these diseases are primarily controlled by application of methodssulfur dioxide. The widespread usage of synthetic fungicides exists the chemical residues, environment pollutions, fungicide-resistant by pathogens, etc, many malpractices. Alternative methods which was effective and innoxious were imminently demanded in the storage of grapes. Microbial biocontrol agents have shown great potential as an alternative to fungicides for the control of postharvest decay of fruits and vegetables.A strain of yeast that has highest biocontrol efficacy on postharvest diseases of grapes in several yeasts which were isolated before were selected to produce biocontrol preparation. The capability of growth of yeasts, the separation and dryness methods in medicament producing,the antagonistic mechanism, the enhancive method of biocontrol efficacy were studied in this paper.The main results are as following1.In all isolated yeasts, Pichia guilliermondii exhibited the best inhibitory activity in vivo,the perfect efficiency of growth on the surface of grapes,and the great potential to produce biocontrol preparation.2. Pichia guilliermondii does not inhibit the pathogens by producing antibiotics;mode of action of P. guilliermondii is competitive for nutrients and space.3.It was made sure by microscope and electron microscope that Pichia guilliermondii could close adsorbed on the mycelium of Botrytis cinerea pers. The filtrate of P. guilliermondii culture medium could not restrain the growth of B. cinerea. The activity ofβ-1,3-glucanase and chitinase could not be seted out in the culture medium of B.cinerea and P.guilliermondii. The antagonistic mechanism of mycoparasitism could not be made sure.4. The activity ofβ-1,3-glucanase and chitinase in grapes could not be enhanced by inoculating P.guilliermondii. Pichia guilliermondii did not inhibit the pathogens by inducing disease resistane of graps.5.The composition of culture medium for Pichia guilliermondii were PDB, fructosel 8g/L, yeast extract paste 2.0g/L, carbamide 2.0g/L, L-D-L- leucine 0.2g/L, KH₂PO₄5.5g/L, MnSO₄4.5mg/L, ZnSO₄ 25 mg/L, niacinamide 0.4mg/L , inositol 120mg/L6.The optimum culture condition for Pichia guilliermondii were 28℃,pH 4.0, inoculum 6%,30h, ventilation volume 2.0 V.V.m, rotate speed 100rpm.7. The optimum protectant for Pichia guilliermondii were sorbierite2% + sucrose ester4% + PG 0.45%.Milk powder was the best carrier in producing yeast medicament.8.The livability of Pichia guilliermondii was 91.6% after Freeze drying. Vaciceprocess was the best drying technics in yeast medicament producing.9. The period of validity of yeast medicamen produced with the culture mediumand condition which were ascertained in this study was 12 monthes. The rotting rate ofgrapes could be reduced to 18% after 12 monthes in cold storage by the treatment of yeast medicament at 1% alone.10. The efficacy of Pichia guilliermondii for control to postharvest mold decay of grapes could not be enhanced by the addition of 2% calcium chloride (CaCl₂), or 2% sodium bicarbonate (NaHCO₃). The efficacy of Pichia guilliermondii for control to postharvest mold decay of grapes was not improved when combined with heat treatment, microwave treatment, edible coating. The rotting rate of grapes could be reduced to 48 % after 4 monthes in cold storage by the treatment of yeast medicament at 1% combined with dimethyl fumarate at 0.025% and MeJA at 0.3%. The combinations could got the same control results as general-dose fungicide got.