SUPPRESSION OF FUNGAL PHYTOPATHOGENS (FUSARIUM SPP AND ALTERNARIA SPP) ON THE TOMATO LEAVES BY THE RHAMNOLIPIDS PRODUCED BY PSEUDOMONAS AERUGINOSA PAO1

Abstract

Suppression of fungal phytopathogens is one of the serious challenges agriculture and forestry since they cause significant biomass and yield losses. One of the alternative methods of suppression phytopathogens is the use of biosurfactants, which are amphiphilic substances produced by many microbes. Bacteria of Pseudomonas genus are known to produce biosurfactants of the rhamnolipid class. These surfactants can possess antimicrobial and fungicidal properties. In this work, we studied the effect of various concentrations of rhamnolipid (100, 500, 1000 mg/l), produced by Pseudomonas aeruginosa PAO1 strain on the growth of fungal pathogens Fusarium oxysporum and Alternaria spp on tomato leaves that were a) separated from the plants and b) not separated from the plants. On infected separated leaves without biosurfactant treatment, the area covered by Alternaria spp and F. oxysporum was 28% and 8%, respectively. The growth of Alternaria spp was fully inhibited when the leaf spayed with 1000 mg/l rhamnolipid before artificial infection, and of F. oxysporum � with 100 mg/l rhamnolipid. On unseparated biosurfactants-untreated leaves that remained growing on the tomato plants after artificial infection with Alternaria spp and F. oxysporum was 4.7 and 4.2 scores, respectively. Infection of the leaves did not lead to infection of the whole plants since infected leaves were defoliated. Interestingly, biosurfactants treatment led to growth stimulation of tomato plants at a concentration of 1000 mg/l. It can be concluded that rhamnolipid produced by P. aeruginosa PAO1 is a promising biocontrol agent.