Screening, Identification Of A Antagonistic Yeast Against Mango Anthracnose And Evaluation Of Its Protectants

Mango anthracnose, caused mainly by Colletotrichum gloeosporioides (Penz) Penz.&Sacc., is considered as one of the most important diseases in mango production. This disease may cause pre-and post-harvest loss of mango fruits. For a long time, chemical fungicides have been used to control the disease, But with the extensive use, C. gloeosporioides has developed resistance to the benzimidazole fungicides, which decreased the control efficiency. It is necessary to open up new, green biological control approach, as people pay more and more attention to environmental protection and food safety.For all biocontrol agents, the yeasts, which usually has a strong resistance to adverse environments, can multiply in nutrient-poor conditions, does not produce antibiotics, can not be much impacted by pesticides, etc., are gradually becoming a hot spot.The purpose of this research is to screen effective antagonistic yeasts against mango anthracnose, to identify the potential yeast strains, to primarily reveal the mechanism of biocontrol, and to make a liquid formulation of the biocontrol agent. The main results are as follows:1. The efficiency of biocontrol agents were tested on mango leaves. The yeast strain,4-4A, isolated from mango surface, was found to strongly inhibit mango anthracnose development with biocontrol efficacies of75%on mango leaves.2. The strain4-4A was identified to be Pichia quilliermondii according to the results of morphological observation, physiological testing and rDNA-ITS sequences analysis.3. The possible mechanism of P. quilliermondii was investigated. Bio-assay results showed biocontrol efficacy of the yeast cell suspension with sterile distilled water was better than those of cell culture and cell-free culture filtrate; The microscopic observation demonstrated that P. quilliermondii tenaciously attached to the mycelium of C. gloeosporioides; The yeast during culturing might produce volatile and non-volatile inhibitory substances inbiting mycelial growth, melanin production and conidial germination of C. gloeosporioides. According to these results, the possible mechanisms of P. quilliermondii might includ nutrient and space competition, producing inhibitory substances against pathogen, attachment to the mycelium of C. gloeosporioides.4. The survival of P. quilliermondii in liquid formulations with sucrose, galactose and trehalose as additive respectively, was measured during storage of12weeks at temperatures ranging from-20℃to25℃. The result showed that trehalose was the most effective protectant. After12weeks incubation at-20℃,54%of the yeast cells were viable,52%and56%at10℃and4℃, respectively. Sucrose was the worst protectant. Combining Vc with the protectants improves the protective efficiency.