Screening of antagonistic bacteria against Erwinia amylovora and its control effect in greenhouse

Abstract:

[Background] Fire blight is a bacterial disease caused by Erwinia amylovora, which is harmful to more than 220 plants belonging to more than 40 genera, such as apple, pear, hawthorn and so on. In recent years, fire blight has occurred in many countries, including central Asian countries. E. amylovora has become an extremely high risk microorganism for China, especially for Xinjiang. Fire blight has been listed in the list of first class crop diseases and pests by the Ministry of Agriculture and Rural Areas of China. [Objective] To screen the antagonistic strains of Erwinia amylovora from Xinjiang and improve the ability of Korla fragrant pear to resist the risk of fire blight. [Methods] The antagonistic strains were isolated from the soil of pear orchard and the bacteria stored in laboratory by confrontation plate method. The strains were preliminarily identified by physiological characteristics analysis as well as 16S rRNA gene sequencing, and the antibacterial effect was rescreened by Oxford cup diffusion method. The control effects were tested on two-year-old potted Pyrus betulaefolia seedlings in greenhouse. [Results] Eleven antagonistic strains were obtained, all of which were Gram positive. Nine of them were Bacillus and two were Lactobacillus. The results of confrontation plate experiment showed that Bacillus velezensis JE7, Lactobacillus plantarum LP1 and Lactobacillus plantarum LP2 had strong antagonistic effect, followed by Bacillus velezensis JE4. The control effects showed that Bacillus velezensis JE4 had the best prevention effect in greenhouse, which reached 73%. The physiological characteristics was showed that JE4 and JE7 could tolerate 1%—7% NaCl and could grow at pH 4.0—9.0; LP1 could tolerate 1%—9% NaCl and could grow better at pH 5.0—9.0. [Conclusion] a batch of bacteria against Erwinia amylovora were screened and obtained. Some of the antagonistic strains had significant control effect in greenhouse and strong saline-alkali tolerance.