Biocontrol of Lasiodiplodia theobromae, which causes black spot disease of harvested wax apple fruit, using a strain of Brevibacillus brevis FJAT-0809-GLX

摘要

A strain of Brevibacillus brevis FJAT-0809-GLX that was isolated from the soil in Yongtai, Fujian Province, PR China, was evaluated for its potential to reduce the black spot decay of wax apple (Syzygium samarangense Merr. et Perry) fruit caused by Lasiodiplodia theobromae using in vitro and in vivo tests. The culture filtrate, unwashed cell suspension (1 x 10(8) CFU/mL) and washed cell suspension (1 x 10(8) CFU/mL) significantly suppressed the growth of mycelium in vitro. The culture filtrate was the most effective treatment for controlling wax apple fruit rot in vivo. The incidence of rot in wax apple fruits that were treated with culture filtrate for 8 days at 30 degrees C was 20% +/- 6.67%, which was markedly lower than that of those that were treated with sterile distilled water (control). A better biocontrol was obtained with a longer incubation time of B. brevis. When the incubation time of B. brevis was 72 h, the disease incidence decreased to 14.44% +/- 1.93%. Furthermore, the best biocontrol efficacy was obtained when the fruits were inoculated with the culture filtrate of B. brevis before inoculation with the pathogen. The chemical composition of the acetone extract from B. brevis culture filtrate by GC-MS analysis showed that there were three major antifungal compounds: ethylparaben, dibutyl phthalate, and 1,2-benzenedicarboxylic acid, mono(2-ethylhexyl) ester. The in vitro antifungal activities of these major components on L theobromae showed that ethylparaben was the main antiftmgal compound. Isolated extracts could be used for the future development of antifungal agents. To the best of our knowledge, this is the first report demonstrating that the bacterium B. brevis could be used as a biocontrol agent against black spot disease by L. theobromae on wax apple fruit. (C) 2014 Elsevier Ltd. All rights