Study On Screening Biocontrol Yeast Against Anthracnose And Stem-end Rot Of Mango In Postharvest

Mango in postharvest is affected by its rapid metabolizing and pathogen attacks. Anthracnose and stem-end rot are primary postharvest diseases of mango fruits. Synthetic fungicide was an effective means of controlling these diseases. However, chemical demerits such as the serious polluting on gas, soil, water, agricultural products and the influence of people's health have been concerned. In addition, the diseases' resistance to common synthetic fungicide increased, which decreased the effects. It's important to study new controlling means.The aims of this research are: screening effective antagonistic yeasts against anthracnose and stem-end rot of mango in postharvest, studying the inhibition effects of the yeasts against mangos' postharvest diseases, then identifying the yeasts which were screened. Main conclusions were drawn as follows:1. A strain against anthracnose and one against stem-end rot of postharvest mango were isolated and screened. After primary and further screening in vitro, 8 strains exhibited inhibitory activity to C. gloeosparioides and 8 strains to B. theobromae. Through Fruits-inoculation test in vivo, it was found that isolates X-1 was the most effective antagonist against C. gloeosparioides and Mo-7 was the best one against B. theobromae. The incidences of disease were 40% and 16.7%.2. Inhibition effects of yeast suspension in different concentration were tested. The results indicated that the inhibition effects increased with the increase of concentration of yeast suspension, the inhibition effect of yeast suspension in 10 CFU/mL was equal to fungicide carbendazim in 200 mg/L. The yeast suspensions in 10~6 and 10~7 CFU/mL also had inhibition effect, the incidence of disease seemed significantly lower than the control.3. Rapid colonization of the isolates was tested. Both the isolates X-1 and Mo-7 colonized rapidly in wounds, the population of antagonists cell increased 10~3～10~4 times within 48h. Pathogenic spores inoculated, the colonization of isolated X-1 became slower, and the population of Mo-7 increased more rapidly than strain inoculated only, the population of every moment was more than the latter.4. The antagonists were identified. Isolates X-1 and Mo-7 through photomicrography and physiological testing. The isolate X-1 was identified as Candida valdiviana, belonging to Beuteromvcotina, Cryptococcaceae, Candida. And Mo-7 was identified as Debaryomyces hansenii, belonging to Ascomycetes, Debaryomyces.