Isolation, Screening And Biocontrol Efficacy Assessment Of Antagonism Yeast Against Postharvest Mango Anthracnose

Anthracnose, caused by Colletotrichum gloeosporioides(Penz.)Penz.&Sacc, is the major postharvest disease of mango in all mango producing areas of the world. The disease seriously affects the quality and appearance quality of mango fruits, and accounts for over70%of the total fruit diseases. Chemical fungicides are the main method used to control the disease. But with the extensive use, C. gloeosporioides has developed resistance to the pesticides and such problems as environmental safety and food safety were increasing seriously, which decreased the control efficiency. Biological control has advantages over fungicides, including safer for the environment and human health, less insecticide resistance, etc. The application of antagonism yeasts instead of fungicides in controlling postharvest disease has being a promising application. However, recent findings showed that little antagonism yeasts were used on mango anthracnose, with less intensive studies and applications. The purpose of this research is to screen out effective antagonism yeasts, enriching the strains resources. The study of inhibition effect and fruit quality was also investigated. The results of the experiments were drawn as following:1-.359strains of yeasts which isolated from the surface, wound, leaf and soil of various fruits in Hainan province were screened for antagonistic activity against postharvest anthracnose of mango fruit caused by C. gloeosporioides.4strains of yeasts screened through the in vitro and in vivo method showed to have stronger antagonistic action on postharvest anthracnose decay of mango fruit. Among them, the yeast strain (number T18) which had the best biocontrol efficacy against postharvest anthracnose of mango fruit was identified as Debaryomyces nepalensis by morphology, physiology, and molecular biology (ITS) method. The inhibition zone reached14.33mm under in vitro condition and in vivo only reached1.58mm.2? At1*107CFU/mL concentration, the inhibitory action of D.nepalensis can bring effective prevention and control of mango anthracnose. The concentrations of D.nepalensis had significant effects on biocontrol effectiveness:the higher the concentrations of D.nepalensis, the lower the disease incidence and the smaller lesion diameter. Considering the economy and fruit quality, the yeast cell suspension at1*1O8CFU/ml was the best concentration.3? Inhibitory action of D. nepalensis immersing time directly influences the disease incidence. Immersing for too short or too long time will increase the incidence of mango anthracnose. The inhibitory action was the best when the immersing time was1h, with the incidence of16.67%, significantly less than the control of75%. 4? After storing at28?for6days, yeasts inoculated48hours before pathogen of mango had a inhibition zone of0.83mm, while the inhibition zone of yeasts inoculated48hours later than pathogen was4.30mm. This demonstrated that yeast inoculated earlier has the better control of diseases than the others.5? After soaking in D.nepalensis suspension, treated mangos had lower disease incidence, and better maintaining of the fruit hardness, soluble solids and ascorbic acid content compared with the control, which effectively slowed down the rise of mango skin cell membrane permeability and the accumulation of MDA, and delayed the maturity of the fruit's ageing process. In terms of two storage temperatures,25?can better maintain the soluble solids, ascorbic acid and MDA content.