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This paper is designed to discover the distributing pattern of the endophytes in tobacco plants, and select bioactive endophytes which have the capability to be anti-tobacco rot-knot nematodes. And four species of high-quality tobaccos, namely K326, G-80, Hong Hua Da Jing Yuan and Jing Ye Huang are used to conduct the experiment, in which the endophytes in their seeds, roots, stems and leaves are isolated, counted and selected. The results are as follows:First, it is found that there are a large amount of endophytes in tobacco, of which endophytic bacterias takes the largest percentage, endophytic actinomycetes the next and endophytic fungus the least. The distribution of them in the soil is the same. Concerning the numbers of the endophytes in different parts of the plant, it is almost the same in the roots and the seeds. Caudexes have the medium amount of endophytes, and leaves have the least. In different species of tobaccos, the distribution of endophytes also varies. When they are still seeds, the number of endophytes in K326 and Hong Hua Da Jing Yuan is considerably high. In Jing Ye Huang, the number is also not small. And G-80 has the least. During the seedling period, there is no obvious distinction among the mentioned four species. However, when they are planted in the field, the number of endophytes in Jing Ye Huang is the smallest. In the plants of tobacco, the kind of endophytes that occupies a large quantity is Gram-negative bacterium, while the number of spore bacteria is higher in seeds.Second, in antagonistic experiment and antiblastic emperiments of Escherichia coli and Staphyloccus aureus, the results show that Endophyte bacterias fermentation broth’s effect on controlling bacterias is not clear. At least, it can not be detected from the experiment.But endophytic actinomycetes and its bacterias fermentation broth are effective.The inhibition diameters of the endophytic actinomycetes Y12 is as wide as 15 mm. in the anti-Staphyloccus aureus experiment, and that of the plant A7 has reached 21 mm in the anti-Escherichia coli experiment. Besides, there are 5 Hong Hua Da Jing Yuan, 1 Jing Ye Huang and 1 K326, which are found to be antiblastically active. All these indicate that the anti-botanic disease and antagonistic characteristics of the four species are to some extent connected with each other. Third, the selected plants which are more antagonistically effective are then used to conduct bacterias fermentation broth antagonistic and the secondary females rot-knot nematodes controlling experiment. It turns out that the Endophyte has no controlling and killing ability. However, its bacterias fermentation broth is obviously effective. In the preliminary experiments, there are 3 plants that can kill all the bactierias, among which the plant H3 is the most effective. When put into 30% bacterias fermentation broth, the plant H3’s ability of killing rot-knot nematodes can reach as high as 100 percent. But the results of endophytic actinomycetes Y12 is not desirable.Forth, H1, H3, K6 and Y12 are selected to conduct root-knot nematodes controlling experiment. It turns out that Endophyte bacterias fermentation broth is more effective than its thallus. But the result of endophytic actinomycetes is the opposite. Ordinarily speaking, Endophyte can promote the growth of plants. But the promoting effect of the Endophyte thallus is larger than that of its bacterias fermentation broth. With disease index of 4.16, controling effect is 91.68%, the H3 Endophyte is best in controlling rot-knot nematodes , which is much better than blank CK and is also better than CK Avermectins. Moreover, the H3 Endophyte’s root-knot nematodes indicator of tobacco is obviously higher than CK Avermectins’.Finally, as the plant H3’s effect is so obvious in the above experiments, it is then used to carry out 16S rDNA identification and ordinary identification. According to 16S rDNA order comparison and the result of morphological, physiological and biochemical characteristics, it is concluded that the plant H3 is probably bacillus cereus.
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