Effect and Components Analysis of Cell Free Supernatant Produced by Bacillus amyloliquefaciens Strain Lx-11 on Rice Plant Growth-promoting

Bacillus amyloliquefaciens Lx-11 is a biocontrol strain which has significant efficiency to control bacterial leaf streak of rice in the field trials. In this study,the sensitive variety Jiangang 30 was used as test material to compare the effects of different dilutions of the sterile supernatant of the Lx-11 strain on seed germination and growht of seedlings in rice. The effect of rice shoot length,root length,plant height,chlorophylls a,chlorophylls b,total chlorophylls and root activity of rice treated with cell free supernatant dilution of Lx-11 were investigated. The HPLC-MS methods were established for the determination of bioactive substances including auxin,abscisic acid,gibberellin and spermidine in suspension of Lx-11 strain filtrated with fiber filters. Results showed that different cell free supernatant dilutions of strain Lx-11 could promote seed germination and seedling growth of rice. The growth promoting effect was varied with the dilution times,with the dilution increased: the role of promoting growth was first increased and then decreased,in which the 100 times dilution was the most significant impact on the morphology and physiological indicators of rice seeds and seedlings,while the dilution of 200 times,the promoting effect reduced. The contents of chlorophyll in leaves and the root activity of plant were increased in different degrees after spraying the different dilutions. The highest was treated by the 100 times dilution,increased by 45. 97% in chlorophyll a,49. 62% in chlorophyll b,46. 95% in total chlorophyll and 225. 43% in root activity,respectively. The supernatant of Lx-11 containing IAA,GAs,ABA and Spermidine,were 1200 ng·mL -1 ,75. 5 ng·mL -1 ,3130 ng·mL -1 and 811 ng·mL -1 respectively,detected in the supernatant of strain Lx-11 by a liquid chromatography-mass spectrometry. In general, B. amyloliquefaciens strain Lx-11 could significantly improve the growth and development of rice plant,and the promotion substance presents mainly in the supernatant. This research provides a theoretical basis for the efficient application of Bacillus amyloliquefaciens Lx-11 in the field of microbial pesticides.