USE OF PSEUDOMONAS AERUGINOSA FOR THE CONTROL OF ROOT ROT-ROOT KNOT DISEASE COMPLEX IN TOMATO

Abstract

The potential of two Pseudomonas aeruginosa isolates (Pa-7 and IE-6) as biological control agents against Meloidogyne javanica at five inoculum densities (0, 500, 1000, 2000 and 4000 juveniles/plant) was tested on tomato in earthen pots. The effects of root knot nematodes and the root-infecting fungi Fusarium oxysporum, F. solani and Rhizoctonia solani on bacterial endophytic colonization (root and shoot) as well as the effect of the bacteria on nematode multiplication, control of the root rot-root knot disease complex and the growth of tomato plants were investigated. The two P. aeruginosa isolates significantly reduced nematode populations and root invasion by the nematode and colonization by the root-infecting fungi on tomato. Both the isolates showed similar results at low nematode densities (500 and 1000 J2) but isolate IE-6 was also effective at the higher nematode densities (2000 and 4000 J2). Bacteria survived well both in roots and stem but increased nematode densities were associated with decreased bacterial populations. A negative correlation between F. oxysporum infection and bacterial root and shoot colonisation was also observed. A progressive decrease in plant growth was observed with an increase in nematode density both in bacteria-treated and untreated plants but damage caused by M. javanica was less in treated plants.