Bacillus subtilis L1-21 as a biocontrol agent for postharvest gray mold of tomato caused by Botrytis cinerea

Gray mold (Botrytis cinerea) is a serious disease causing considerable losses to harvested tomato during storage and transportation. Extensive and unjudicial use of fungicides has certain deleterious effects such as evolved resistance in pathogen and environmental pollution. The ice cold chain transportation is the most commonly used method, but the results are not satisfactory. Currently, the trend is shifting towards prevention and control measures which ensures environmental protection, therefore, the biological control of postharvest diseases has become a hot spot. In this study, Bacillus subtilis L1-21 was used to control gray mold on tomato fruits, by adopting plate confrontation and fruit acupuncture method. To evaluate the preservative effect of biocontrol agent L1-21 on tomato, the gfp-tagged L1-21 was used to study colonization potential in harvested tomatoes assay. Colonization of L1-21-gfp in postharvest tomatoes was stable at 103 cfu/g by soaking and fluorescence method. Whereas inhibition rate of B. cinerea was 39.63% ± 4.73% in plate confrontation. Culture suspension of L1-21 at a concentration of 108 cfu/ml displayed the best control effect: 86.57% ± 2.55% against tomato gray mold. In addition, different components exhibited different results such as cell pellet + saline (72.94% ± 8.49%), supernatant (41.18% ± 16.22%), sterilized culture (28.56% ± 6.54%). Further, suspension of B. cinerea and Bacillus L1-21 injected in tested tomatoes led to maximum control effect (81.40% ± 2.74%) after 4 h. Injection of L1-21 culture into tomato followed by pathogen B. cinerea spore solution resulted in 100%±0% control effect after 48 h. There was no significant difference in fruit quality between treated and untreated tomatoes. Taken together, B. subtilis L1-21 may lay theoretical foundation to be used in prevention of gray mold and other postharvest diseases during storage time.