| Tomato gray mold is one of the most important diseases caused by Botrytis cinerea, responsible for severe pre-and post-harvest losses for tomato production. Use of yeast to control gray mold on tomato is a feasible approach. Candida intermedia C410is a yeast strain with antagonism to Botrytis fruits rot of strawberry. However, biocontrol potential of C410in suppression of gray mold of tomato has not been assessed so far. In addition, population dynamics of the yeast strain C410in plastic tunnels should be determined in order to develop this yeast strain in biocontrol of tomato gray mould disease. A study was conducted to determine the biocontrol efficacy of C410in suppression of tomato gray mould, to investigate population dynamics of C410on flowers of tomato in plastic tunnels and to formulate C410. The results achieved are summarized below:1. A series of laboratory tests were carried out to evaluate biocontrol efficacy of yeast strain C410against gray moud of tomato. Different concentrations of C410yeast cell suspensions and Botrytis cinerea conidia were mixed, inoculated in YPDA medium plates, tomato fruits and tomato leaves. Results showed that in a certain range of concentration as3×108,3×107and3×106cells/mL, the yeast strain C410inhibited germination of B. cinerea conidia and the subsequent hyphal growth, disease incidence on tomato fruits and leaves. Nutrient competition may be an important mechanism by which C410inhibited infection of tomato caused by B. cinerea.2. Survival of the yeast strain C410on flower petals of tomato in plastic tunnels at the full-bloom stage was monitored through isolation using selective medium. C410yeast cells could adapt to the changeable environment with fluctuated temperature and humidity. The strain could colonize the surface of petals at least5days until tomato flowers withered. Ripening tomato fruits with different treatments were weighed. The results showed that the C410treatment on flower petals increased the tomato fruit weight by about24.8%.3. Stability of the biocontrol efficacy for the yeast strain C410was studied under the field conditions. Plot experiments and field tests were carried out in2013and2014in Wuhan, Wuxue, Xianning and Macheng of Hubei Province. Results showed that the treatment with the C410cell suspension was effective in controlling gray mold of tomato in Wuxue and Xianning, but not in Wuhan and Macheng, where the incidence of tomato gray mold was too low.4. The biocontrol effects of C410on biological characteristics of tomato plants such as plant height and yield were investigated. Results revealed that C410treatment on flowering-plants did not produce any negative effects on tomato growth and development.5. Liquid formulation suitable for yeast cell survival was studied. The initial storage concentration, storage temperature and further biocontrol stability were studied. Analized results showed that, while the initial preserving concentration was2×109CFU/mL, storage temperature was4℃, liquid formulation of C410with high viability of cells were phosphate buffers supplemented with5%trehalose and1mM ascorbic acid. The liquid formulation kept high viability of yeast cells for more than90days. Suspensions of liquid formulation after90days and fresh yeast cells were tested against B.cinerea on tomato fruits, both suspensions exhibited prospective biocontrol effect, gray mould of tomato was inhibited while the quality of tomato fruits maintain completely good.The above-mentioned results laid a solid foundation for applying the yeast strain C410to control tomato gray mold disease. |
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