Protection of Eggplant and Chilli from Bacterial Wilt (Ralstonia solanacearum) with Antagonistic Bacteria

摘要

Bacterial wilt caused by Ralstonia solanacearum is one of the limiting factors in eggplant and chilli production in Indonesia. Control of the disease is difficult with the available means. Biological control based on antagonism was therefore chosen as one of the control methods. A fluorescent pseudomonad (Pseudomonas putida, Pf-20 strain) isolated from the rhizosphere of Mimosa invisa proved successful in suppressing R. solanacearum in vitro, reducing disease intensity in greenhouse and field experiments. However, the degree of protection was low. The use of more than one species of microorganisms to control plant pathogens likely enhances the protection level. An avirulent-bacteriocin producing strain of R. solanacearum (Rs~(-1)27) was chosen as a companion of Pf-20 to control the disease. Rs~(-1)27 inhibited the growth of other R. solanacearum isolate, with an inhibition zone of 12 mm, and as much as 86% of other isolates were inhibited. Rs~(-1)27 did not inhibit the growth of Pf-20 in YPGA and CPG medium. However, Pf-20 inhibited the growth of Rs~(-1)27 in King's B medium with an inhibition zone of 15 mm, but did not work in YPGA and CPG medium. The greenhouse test showed that dipping the root system of eggplant and chilli in bacterial suspension of Rs~(-1)27 and Pf-20, both solely and in combination, were able to suppress the disease and prolong the incubation period. In the control plots, plants began wilting one week after transplanting. In the plots treated with Pf-20 and Rs~(-1)27, the diseased plants were first observed at two and five weeks after transplanting, with a disease index of 13 and 16, respectively, while in the control plots, the disease index at that time had already reached 56. When Pf-20 and Rs~(-1)27 were combined, the disease was first observed at 5 weeks after transplanting with a disease index of 6.