Isolation and identification of Ralstonia solanacearum-22 and its antagonistic bacteria in tobacco plantations of Yunnan province

Abstract:

[Background] Tobacco bacterial wilt disease caused by Ralstonia solanacearum is a typical soil borne bacteriosis, which widely occurs in the tobacco farms in south of China. Biological control is an effective measure to alleviate the occurrence of the tobacco wilt disease; however, the antagonistic agents still lack. [Objective] To identify the R. solanacearum isolates in tobacco plantations of Yunnan province, and to screen its antagonistic bacteria for biocontrol of tobacco wilt disease. [Methods] R. solanacearum was isolated and identified from the infected tobacco tissues from the farms in Yunnan province by the plate dilution method. Antagonistic bacteria were isolated by the plate confrontation method and the antagonism against wilt disease was investigated under laboratory and field conditions. [Results] The R. solanacearum strain RS-22 was isolated from the infected tobacco plant stem. Koch’s postulates was employed to further confirm the causal agent of the wilt disease. The antagonistic microorganism screening led to the discoveries of 12 biocontrol bacteria. Among them, the strain Y4, a Bacillus amyloliquefaciens, showed the strongest antagonistic effect to RS-22. Pretreatment of the tobacco or tomato plants by root irrigation significantly enhanced their resistance to the bacterial wilt disease. Moreover, syringe injection of Y4 could significantly promote the survival rate of the RS-22 infected N. benthamiana plants. Field application of Y4 remarkably alleviated the wilt disease in the tobacco farms in Wenshan county of Yunnan province. [Conclusion] RS-22 has a broad spectrum pathogenicity. Y4 significantly suppressed the growth of RS-22 and has excellent biocontrol effect on the RS-22 infection. This study provides a useful tool for the biological control of tobacco wilt disease.