Specific Identification, Growth Conditions Of Antagonistic Bacteria Against Botrytis Cinerea And Their Colonization On The Surface Of Tomato Plants

Three strains of bacteria antagonistic highly against Botrytis cinerea Per. were isolated from tomato leaves and soil. According to the morphological. physiological and biochemical features, the isolate W10 was identified as Bacillus licheniformis (Weigmann) Chester and the isolates W3 and Y2-11-1 belonged to Paenibacillus polymyxa (Prazmowski) Ash et al. It is first reported that these bacterial species had antagonism to B. cinerea on vegetables in China. The growth conditions of these antagonistic bacteria had been studied. The optimum culture time for antibiotic bacteria ranged from 24 to 72 hours. The optimum growth temperature was from 27 to 30癈. The optimum growth pH values in the media was from 7 to 8.According to the experimental results and economical factors, the best commercial production medium of strain W10 was made up of maltose 1%. soybean cake powder 4%. NaNO3 0.2%, K2HPO4 0.02% and yeast extract 0.05%; that of W3 consisted of sucrose 2%, soybean cake powder 4% and yeast extract 0.4%; that of Y2-11-1 was composed of maltose 1%, soybean cake powder 2%, NaNO3 0.2%, K2HPO40.02% and yeast extract 0.2%.Three antagonistic bacteria were induced to be resistant to rifampicin and used to study the colonization on the surface of tomato plants. The colonizing ability of antagonistic bacteria was related to plant parts, introduced bacterial concentration and environmental factors. About 10-15 days after introducing antagonistic bacteria, they could be detected from tomato phylloplane. The colonizing capacity of antagonistic bacteria on tomato fruit surface had positive Riationship to the introduced bacterial concentration. The higher bacterial concentration introduced, the bigger population andthe longer time of bacterial colonization. Except strain W10, other antagonistic bacteria could be detected from 10 to 15 days after introduction at high concentration (109cfu/ml).Contrasted with inoculating antagonistic bacteria only, inoculation of Botrytis cinerea had some influence on the colonization of antagonistic bacteria. But the effect of inoculating antagonistic bacteria before B.cinerea was smaller than that of inoculating B.cinerea and bacteria together and inoculating antagonistic bacteria after B.cinerea. This showed that there were competitions in nutrition and space between antagonistic bacteria and B.cinerea. It also indicated that the prevention of antagonistic bacteria was better than their cure for grey mould.Temperature, relative humidity and illumination had significant effects on the colonization of antagonistic bacteria. The optimum conditions of three strains were consistent as a whole. The optimum relative humidity was from 95% to 100%. The optimum light time was 12 hours for each day. The optimum temperature ranged from 25℃ to 35℃. In lower temperature the bacteria could not grow and colonize well on tomato plant. In the condition of continuous darkness or illumination, the colonization of bacteria was weaker than that of light for 12 hours a day. In general, the growth and colonization of antagonistic bacteria required high humidity. The higher relative humidity, the better colonization of antagonistic bacteria.