Evaluation of the efficacy of chitosan and Paenibacillus polymyxa for control of tomato bacterial wilt under greenhouse environment

Abstract

In this investigation we used antagonist bacteria and Chitosan as a seed treatment and soil drench to evaluate their effect on Ralstonia solanacearum in-vitro and under greenhouse conditions and their effect on enzymes activities. Sixteen strains ofpaenthaedius sp. were screened in-vitro for their antagonistic activity against R. solanacearum; only two have shown different degrees of antagonism. Paenibacillus polymyxa strain MBO2-1007 showed the highest degree of inhibition in-vitro was selected for further study in the greenhouse. Accordingly, P polvmyxa and chitosan significantly reduced wilt incidence by 88.21% and 61.38% as a seed treatment and by 82.31% and 76.66% as a soil drench, respectively, compared to the control. For tomato biomass P polynlyza and chitosan significantly promoted plant height by 53.36% and 49.86% as a seed treatment and by 54.52% and 48.74% as a soil drench respectively, and also increased the fresh weight by more than 188.97% and 138.55% as a seed treatment and by 175.74% and 165.15% as a soil drench respectively, and increased dry weight by more than 100.38 and 85.74% as a seed treatment and 97.61% and 95.74% as a soil drench respectively. Moreover, significant increases in activities of plant defense enzymes included B-1, 3-glucanase and chitinase were recorded in treated plants compared with untreated control. It was noticed that Chitosan soil drench was more effective than seed treatment, and high reduction of wilt disease was obtained with P. polymyxa strain IvIB02-1007 in two methods of application. This is the first report of using chitosan as a potential biocontrol agent for Ralstonia wilt of tomato under greenhouse conditions.