Biological control of postharvest diseases of apples, peaches and nectarines by Bacillus subtilis S16 isolated from halophytes rhizosphere

Penicillium expansum, Botrytis cinerea and Colletotrichum acutatum are the most common postharvest pathogens of apples, peaches and nectarines. In this study, 96 bacteria were isolated from halophytes rhizosphere and assayed for biocontrol activity under in vitro conditions. Among the 96 isolates tested, isolate S16 effectively inhibited the growth of P. expansum, B. cinerea and C. acutatum. The isolate S16 has reduced 78.33+/-1.53 to 82.98+/-2.13% of disease severity in apples, peaches and nectarines. Matrix-assisted laser desorption ionisation-time of flight mass spectrometry of the antifungal compounds revealed three lipopeptide complexes, namely surfactins, iturins and fengycins. Lipopeptides and hydrolytic enzymes produced by the isolate S16 play an important role in the antifungal activity. Polymerase chain reaction analysis using ituD, srfAD, fenD and fenE gene-specific primers showed that the isolate S16 carry sequences similar to ituD, srfAD, fenD and fenE genes. Based on the 16S rDNA sequencing, the effective isolate S16 was identified as Bacillus subtilis.