ISOLATION OF FLUORESCENT PSEUDOMONADS, HEAT TOLERANT AND CHITINOLYTIC BACTERIA IN BANANA RHIZOSPHERE WITH ANTAGONISTIC ACTIVITIES AGAINST Fusarium oxysporum f. sp. cubense IN VITRO AND MOLECULAR IDENTIFICATION OF SELECTED ISOLATES

Fusarium wilt disease caused by Fusarium oxysporum f. sp. cubense (Foc) race 4 is the most destructive disease of banana in Indonesia. Ecological studies on the disease in relation to the bacterial population in the rhizosphere, is still limited. The rhizobacteria could be exploited as the biocontrol agents to suppress the growth of the pathogen. This experiment was conducted to observe the abundance of fluorescent Pseudomonads, heat tolerant, and chitinolytic bacteria in the banana rhizosphere and assess their antagonistic activities against Foc in vitro. The bacterial population was calculated by serial dilution and plate-count method. The antagonistic test was observed using dual culture method. The average populations of non-fluorescent, heat tolerant, and chitinolytic bacteria in healthy banana rhizosphere were significantly higher compared with those in the diseased plants, while fluorescent Pseudomonads population did not show significant difference from control (the diseased plants). Among the fluorescent Pseudomonads, isolate KB2 produced the widest inhibition zone against F. oxysporum f.sp. cubense, while among the isolates of chitinolytic and heat tolerant bacteria, isolate CH4 and TSA3 caused the highest inhibition of mycelial growth and the least mycelial growth of F. oxysporum f.sp. cubense at 3 days after inoculation (DAI), respectively. Thos