Antimicrobial Effects Of Volatiles Produced By Two Antagonistic Bacillus Strains On The Anthracnose Pathogen In Postharvest Mangos

Mango is valued for its color and enjoyed for its taste and nutritional value. Anthracnose,caused by Colletotrichum gloeosporioides (Penz.), is the most prevalent postharvest diseaseaffecting the marketability of mango. At present, the control of anthracnose disease inmangos remains reliant on fungicides, some alternative or complimentary physicochemicalapproaches, antagonistic microorganisms and so on. Recently, volatile organic compounds(VOCs) produced by microorganisms have been evaluated as a new approach for postharvestdisease control. However, limited research information is available related to the efficacy ofbiofumigation volatiles for the control of mango anthracnose pathogen.The objective of this study was to select effective antifungal volatile-producing strainsfrom various rhizosphere microbes as the potential biological agents, evaluate the effects ofmycofumigation produced by these strains on C. gloeosporioides in vitro and in vivo. A solidphase micro-extraction syringe was used to trap volatiles, and identified them by the GC-MSprocess. The key volatiles that could be used to suppress pathogens were identified.(1) Four bacterial strains of Bacillus spp. which were antagonistic to the mangoanthracnose pathogen were isolated and screened. In vitro, the anthracnose fungus showed88.87%and80.07%of mycelia growth inhibitions in presence of TB09and TB72,respectively. In vitro, the anthracnose pathogen was inhibited effectively by volatilecompounds synthesized by TB09and TB72.(2) TB09and TB72were identified by16S rDNA sequence as Bacillus pumilus andBacillus thuringiensis, respectively.(3) Based on the Gas Chromatography-Mass Spectrometer (GC-MS) analysis,2-nonanone,2-decanone, β-benzeneethanamine,2-methylpyrazine, thymol and so on existedin the samples. Among them, five volatiles,2-nonanone,2-decanone, β-benzeneethanamine,2-methylpyrazine, thymol, showed better inhibition effects on the pathogens. If the drugfumigating effect was removed, only the group of2-methylpyrazine has growth phenomenon.The inhibition rate of40μL L-1artificial mixture of5volatiles was98.75%in the plate test.Alternative2-nonanone, β-benzeneethanamine,2-decanone and2-methylpyrazine with thesame volume sterile water separately, the pathogen hyphae would not grow, however, replace the thyme by the sterile water, the mycelial growth inhibition rate reduced to65.57%from100%.(4) The results showed that the two screened antagonistic bacteria, and some of their producedvolatiles and artificial mixtures could control anthracnose in harvested mango fruit.In the in vivo test, the artificial mixture of5volatiles has come to be considered a safealternative to control mango anthracnose disease. It can effectively control the degree ofrotting, the incidence of the disease, the commodity rate and the rate of edible fruit.