Selection Of Microorganisms Resistant To Wilt Disease Of Tobacco And Research On The Properties Of Antibionts

China has laregest tobacco grown areas and yields in the world and tobacco, an important cash crop in our country, is one of the major sources of farmers' income in tobacco-grown areas and national and local revenues.Wilt disease, the cancer of tobacco plants, is one of the main serious diseases of tobacco, which was first found in American in 1880. The disease is now widesprease in the Southwest China and the yields of tobacco were decreased by 80％sometimes in the case of seriouse disease occurance.We isolated 15 microorganims from tobacco grown soils with variable occurance of wild disease in Guizhou province. 1 actinomycete and 2 fungi most resistant to Pseudomonas solancearum were selected from them by culturing them in solid mediums. The antibionts produced by the three microorganisms in culture solutions were examinated.Among the 15 microorganisms including 3 bacteries, 3 actinomycetes and 9 fungi varied with the antibiosis to Pseudomonas solancearum inoculatedon the liquid mediums. Actinomycetes and fungi generally have stronger ones to Pseudomonas solancearum than bacteries. It is woth pointing out that antibacterial action of microorganisms isolated from neutral purple soils was very strong, strong from calcareous yellow soils and less strong from yellow soils isolated, which is controry to the occurance of wilt disease, i.e. yellow soils＞Calcareous yellow soils＞neutral purple soils. According to the diameters of antibacterial circle on solid mediums, 1 actinomycete and 2 fungi, namely A-01, F-01和F-02, were selected for further studied.Antibionts were detected from fermentation solutions for culturing three microorganisms, rspectively. The growth of Pseudomonas solancearum cultured in liquid soulutions was inhibited by adding the fermentation solutions. Antibibacterial action of fermentation solutions changed in following sequence: F-02＞F01＞A-01.Antibionts could be detected in liquid fermentation at the growth start of the microorganisms(24h after inoculation) and the rate of efflus increased as the time prolonged. The peak of antibiont production was from 48h to 120h following cultureing and thereafter decreased.Antibionts produced the the three microorganisms varied the abtibibacterial action following purification procedure by centrifugation, super-filtration and concentration. The abtibibacterial activities changed in following sequence: F-02＞F01＞A-01, 20 times differences. Antibionts produced by F-02 was heat stable. No significant difference in the abtibibacterial activity was found under temperature at 5to 120℃. It could thus sugest that the antibionts roduced by F-02 was not protein like substances.pH influenced the activities of antibionts produced by F-02. They lost activities in alkline solution and showed activities in acidic one, particularly at pH from 4 to 5.The activities of antionts profuce by F-02 decrease as time prolonged at room temperature. A sgnificant decrease was detected at 21 days at room temperatuere and 10％of avtivities was reduced in this case.Disease occurance rate, index and effect of provention and control of tobacco wilt disease were improved by adding fermentation liquid of F-02 in a small scale field experiment...