Effects of Fengycins and Iturins on Fusarium oxysporum f. sp. physali and Root Colonization by Bacillus velezensis Bs006 Protect Golden Berry Against Vascular Wilt

Abstract

Bacillus velezensis Bs006 has shown antagonistic activity on Fusarium oxysporum f. sp. physali and biocontrol activity against Fusarium wilt (FW) in golden berry (Physalis peruviana). We hypothesized that strain Bs006 has the ability to synthesize antimicrobial cyclic lipopeptides (CLPs) like other members of the same species. However, if so, the real effects of CLPs on F. oxysporum f. sp. physali and their potential as a biocontrol tool against Physalis-FW have not been elucidated. In this study the CLPs profile of Bs006 in liquid culture and antagonist–plant–pathogen interactions were characterized. Also, the potential effects of supernatant free of bacteria against F. oxysporum f. sp. physali and FW were explored and compared with the effects of pure CLPs. Ultraperformance liquid chromatography–electrospray ionization–mass spectrometry analysis revealed the capacity of Bs006 to synthesize homologous compounds of iturins, surfactins, and fengycins in liquid culture and on the inhibition zone against F. oxysporum f. sp. physali in dual confrontation tests. Bs006 supernatant reduced the germination and growth of F. oxysporum f. sp. physali and caused vacuolization, swelling, and lysis of F. oxysporum f. sp. physali cells in a concentration-dependent manner. Pure fengycins affected the development of F. oxysporum f. sp. physali from 11 mg/liter and iturins from 21 mg/liter. In a gnotobiotic system, Bs006 colonized the root surface of golden berry, inhibited the growth of F. oxysporum f. sp. physali, and produced CLPs. Individual application of Bs006 and supernatant protected the plants from F. oxysporum f. sp. physali infections by 37 to 53%, respectively. Meanwhile, fengycins reduced the disease progress by 39%. These results suggest further studies to select an optimum combination of Bs006 and supernatant or CLPs, which might be a good option as biofungicide against F. oxysporum f. sp. physali.