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

Abstract

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. Iological control based on antagonism was therefore chosen asone of the control methode. A fluorescent pseumonad (Pseudomonad putida, Pf-20 strain) isolated from the rhizosphere of Mimosa invisa proved successful in suppressing R. solanacearum in vitro, reducing disease intensity in greenhouse andfield 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-127)waschosen as a companion of Pf-20 to control the disease, Rs-127 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-127 did not inhibit the growth of Pf-20 in YPGA and CPG medium. However, Pf-20 inhibited the growt of the Rs-127 in King,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-127 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 wee after transpanting. In the plots treated with Pf-20 and Rs-127, 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 plot, the disease index at that time had already reached 56. When Pf-20 and Rs-127 were combined, the disease was first observed at 5 weeks after transplanting with a disease index of 6.