EFEKTIVITAS BEBERAPA ISOLAT PSEUDOMONAD PENDARFLUOR UNTUK MENGENDALIKAN PENYEBAB PENYAKIT BUSUK BATANG BERLUBANG Erwinia carotovora subsp. carotovora PADA TEMBAKAU

Abstract

Erwinia carotovora subsp. carotovora, the causative agent of hollow stalk disease, is one of important disease on tobacco. Until now, there is no effective pesticide to control this disease. One among the control agents, which is well recognized, is by fluorescent pseudomonads because is easily isolated and has an antagonistic ability to some pathogens. Although a lot of researches are to isolate fluorescent pseudomonads and have been commercialized, however the fluorescent pseudomonads generally was specific antagonist to some pathogens. The aim of this research is to isolate fluorescent pseudomonads from Sukorambi (SA), Gebang (GB), Sukowono (SC), Mumbulsari (MD) areas. The isolates were test in vitro by hypersensitive reaction (HR), Gram, and fluorescence. In vivo experiment was done with randomized complete design (RCD) and symptoms on leave and stalk were observed to obtain disease severity and incubation period. Forty-five fluorescent pseudomonads were isolated from Sukorambi (SA), Gebang (GB), Sukowono (SC), Mumbulsari (MD), and twelve isolates were selected based on the strong of fluorescence. All the isolates were negatively hypersensitive reaction on tobacco leave and had Gram negative. These isolates were able to inhibit E. carotovora subsp. carotovora growth with vary in diameter of inhibition. Isolates from MD, especially MD2 had the longest diameter of inhibition with range of 12,3 mm - 13,2 mm. In vitro experiment, all the fluorescent pseudomonads isolates have inhibition mechanism of bacteriostatic as showed turbidity on the 1% water peptone after incubation for 48 hours. Based on the screening result on diameter of inhibition, three isolates were chosen from the in vivo experiment. Tobacco plant inoculated with three isolates of fluorescent pseudomonads (GB3, SC2, and MD2) and E. carotovora subsp. carotovora were started to show the wilting leave from 9 days post inoculation (dpi). Isolates GB3 and SC2 showed earlier symptom (9 dpi) than isolates MD2 (15 dpi). Moreover, isolate MD2 was also delayed the incubation period for six days compare with isolates GB3 and SC2. The isolate MD2 also reduced the disease severity to 41,7% compere to isolates GB3 (58,3%) and SC2 (58,4%). In summary, fluorescent pseudomonads isolates from Mumbulsari, especially isolate MD2, was more effective to control E. carotovora subsp. carotovora than isolates GB3 and SC2.