| Tomato, a widely planted fruit-vegetable in our country, plays an important position in our vegetable food industry. The occurrence of tomato diseases is the important problems in tomato production, storage, transportation and sale. Tomato gray mold caused by Botrytis cinerea is a serious worldwide disease in tomato industry. This disease developed and spread rapidly. Pathogen can infect stems, leaves, flowers, fruits and other parts of tomato, the fruit is mainly harmed. Moreover, B.cinerea can lurk in tomato fruits, do harm after picking in the process of storage and transport, becoming a major problem in tomato production.Chemical agents are long-term used as the main means of controlling B. cinerea.However, application of chemicals has many drawbacks.The unreasonable use of chemicals not only causes environmental pollution, but also the adverse effect to the health of people owing to drugs residues. Therefore, biocontrol, as an effectively new means to control the occurrence of disease, received widespread attention.With the studies of biological control and tomato B. cinerea deepening, many antagonistic microorganisms and its metabolites were screened for study. Biocontrol yeast, owing to its strong resistance, non-toxic and other advantages gets people’s attention. The depth study of controlling effect and mechanism of biocontrol yeast is propitious to disease prevention and development of biocontrol agents.The main findings of this study are as follows:1. In this study, we used three biocontrol yeasts conserved by our lab to do different treatment with B. cinerea. Through in vitro tests such as confrontation, storage tests on tomato fruits and in vivo antibacterial tests, we study the controlling effects and mechanisms of biocontrol yeast.In vitro test results showed that:three biocontrol yeasts cannot produce potent anti metabolitesto do inhibition and killing effects on B. cinerea, but they can weaken B. cinerea growth in the solid culture substrate; using micro counting and weighing method study the spore germination and mycelial growth, demonstrating that no living cell culture supernatant and inactivated bacteria had no significant effect on spore germination, while high concentrations of yeast suspension can effectively inhibit B. cinerea spore germination, inhibitory effect of bacteria was positively related to the bacterial concentration; biocontrol yeasts can significantly inhibit B.cinerea mycelial growth, Ca63, Ca64and yett1006inhibited the growth of three biocontrol yeasts amount of B. cinerea hyphae was respectively88.6%,90.7%and85.7%; in vivo test results showed that:three biocontrol yeasts had good adaptability in tomato fruit surface and the wound, they can rapid colonization and growth and also can effectively inhibit the growth of B.cinerea in the fruit of the wound, reduce the disease index and the incidence of the disease. Tomato fruits, treated with biocontrol yeast suspension, had the significant lower decay and weight loss rate. Fruit quality related indicators including vitamin C content, titratable acid and soluble solids had no adverse change in the storage period of20d, suggesting that three biocontrol yeasts had no adverse effects on fruits.The results of in vitro test and in vivo test meanwhile showed that one of the main mechanisms of three biocontrol yeasts inhibit pathogens through competition for nutrients and space conditions, rather than by secreting antibiotics and parasitic effects.2. Using biocontrol yeast suspension and strain t08016b spore suspension to treat tomato fruits with different methods of repeated spraying to investigate the induced resistance mechanisms of biocontrol yeast on tomato fruits. In different treatment groups, tomato defense-related enzyme activities had significant differences. The results showed that:three biocontrol yeasts were able to induce elevation in activity of defense-related enzymes in tomato fruits such as PAL, PPO and POD. The content of active oxygen also increased, further enhancing the fruit’s resistance to disease. In three biocontrol yeasts, the ability to induce defense-related enzymes of Ca64was better than the other two. |
