Application Research Of Bacillus Amyloliquefaciens 41B-1R Of Cotton Endophytes

Plant diseases have been a limiting factor of crop high and stable yield. Chemical pesticides have played a key role in diseases control. As people increasingly pay attention to environmental problems, biocontrol agents are gradually researched and applicated as a method to reduce or partial substitute chemical pesticides. Application of biocontrol agents from biological sources to combat plant diseases is great advantageous, such as natural, pollution-free and biodegradable, and gradually becomes a research hotspot in both domestic and overseas. Biocontrol formulation is a key step for biocontrol agents from the laboratory to the field, and plays an important role in the industrialization of microorganis-ms. Bacillus amyloliquefaciens 41B-1 had been isolated from the cotton plant and is an antagonistic bacteria against cotton Verticillium wilt caused by the soil inhabiting fungus Verticillium dahliae (Kleb.).In this paper, the rifampicin (Rif) resistant mutant of Bacillus amyloliquefaciens 41B-1, Bacillus amyloliquefaciens 41B-1R, was used as antagonistic bacteria. The dynamics of Bacillus amyloliquefaciens 41B-1R was monitored in six months, after the fermentation of 41B-1R was mixed with nursery substrate. Biocontrol bacteria were mixed in nursery substrate to raise cotton seedlings of Sumian 22 and Zhongmian 41, to research the colonization ability in cotton seedling roots of Sumian 22, Zhongmian 41 and the ability against Verticillium dahliae (Kleb.). and the effects on growth cotton seedlings of Sumian 22, Zhongmian 41. The broad-spectrum resistance of the strain against other plant pathogens was investigated and Bacillusamyloliquefaciens 41B-1R wettable power was preliminary studied. Whether common chemical fungicides effect the biomass of bacteria and spores produced of Bacillus amyloliquefaciens 41B-1R was studied. The main results available were summarized as follows:1. Bacillus amyloliquefaciens 41B-1R was mixed in nursery substrate through secondary fermentation. When the relative humidity was down to 28%, the nursery substrate mixed with Bacillus amyloliquefaciens 41B-1R was stored at room temperature. After six months, the biomass of Bacillus amyloliquefaciens 41B-1R was more than 107 cfu/g. The seeds of Sumian 22 and Zhongmian 41 were sowed in the nursery substrate mixed with Bacillus amyloliquefaciens 41B-1R, the growth status of cotton seedlings was similar with CK's, respectively. A large number of Bacillus amyloliquefaciens 41B-1R colonized in the roots of Sumian 22 and Zhongmian 41. The seedlings of cotton were transplanted into pot inoculated with Verticillium dahliae(Kleb.)(V 1070). Compared to the control, the colonization of Verticillium dahliae(Kleb.) was significantly reduced and the disease index was significantly declined. In greenhouse trial, the control efficiency was up to 46.7% and 28.6% in Sumian 22 and Zhongmian 41, respectively.2. Bacillus amyloliquefaciens 41B-1R could inhibit the growth of Fusarium graminearum, Sclerotium rolfsii, Magnaporthe grisea, Phytophthora, the inhibitory action were measured by filter paper cultivation. In particular, the inhibitory zone of 41B-1R on Magnaporthe grisea was wider, indicating that Bacillus amyloliquefaciens 41B-1R was potential to control rice foliar diseases caused by Magnaporthe grisea.3. In the study of Bacillus amyloliquefaciens 41B-1R wettable power, the carriers were screened. Diatomite, white carbon black and attapulgite had certain compatibility with Bacillus amyloliquefaciens 41B-1R. After dried at 54? accelerated storage for 14 days, there was no significant difference in the biomass of bacterial. The early-type powder was stored at room temperature for three months, the biomass of Bacillus amyloliquefaciens 41B-1R was 5.7×108 cfu/g in white carbon black,9.0 × 108 cfu/g in diatomite,1.9×109 cfu/g in attapulgite, respectively. Bacillus amyloliquefaciens 41B-1R wettable power had a preventive effect in Rice seedling blast. The screening of Bacillus amyloliquefaciens 41B-1R wettable power additives, such as wetting agents, dispersants and spores protection agents, will need further studied.4. Among the tested common chemical fungicides, the other 9 kinds for Bacillus amyloliquefaciens 41B-1R had a different degree of inhibition but were not able to kill it completely. Azoxystrobin did not affect the growth of Bacillus amyloliquefaciens 41B-1R in this test. In order to avoid affecting the potential of 41B-1R on plant pathogens, the application method of chemical fungicides should be assessed.