Journal of Pure and Applied MicrobiologyVol. 9 No. Special Edition Nov. 2015

Screening of Phylloplane Bacteria to Control Target Spot Disease of Tomato in Thailand

W. Sutthisa1*, P. Janloy1 and J. Dodgson2

1Department of Biology, Faculty of Science, Mahasarakham University, Kantarawichai District, Maha Sarakham Province, 44150 Thailand. 2Faculty of Science, Mahasarakham University, Kantarawichai District, Maha Sarakham Province, 44150 Thailand.

Received on 08 June 2015 and accepted on 24 September 2015

 

ABSTRACT

The objective of this study was to screen phylloplane bacteria for the control of Corynespora cassiicola, a causal agent of target spot disease of tomato. Phylloplane bacteria were isolated from tomato leaves by washing and after dilution they were spread on four media: potato dextrose agar (PDA), nutrient agar (NA), yeast malt agar (YM) and arginine glycerol mineral salt agar (AGMA). Twenty-nine bacterial isolates were obtained and their ability to inhibit the growth of C. cassiicola was tested in vitro. The results showed that six isolates effectively controlled mycelium growth by 45.01-51.11% inhibition in dual culture on PDA. All effective isolates were tested for their control of target spot disease using the detached leaf technique by spraying a conidial suspension of C. cassiicola (104 conidia/ml) 24 hr before or after application of the phylloplane bacteria (108 cell/ml). We found that antagonistic bacterial isolates BB47, BC29, BC30, BC35, BCP36 and PT4 effectively reduced the disease incidence from 25.00 to 45.00%. Mechanistic studies of cell suspensions of phylloplane showed that the bacteria could inhibit spore germination and mycelial growth of C. cassiicola, the culture filtrate gave a similar result as well. Identification of the phylloplane bacteria by morphology and biochemical tests showed that BC29, BC30, BC36 and PT4 were gram-positive and classified into the genus Bacillus, while BB47 and BC35 were gram-negative and classified into the genus Pseudomonas.

Keywords : Antagonistic bacteria, Bacillus sp., Corynespora cassiicola, Pseudomonas sp.