The combination of Bacillus amyloliquefaciens and Purpureocillium lilacinum in the control of Meloidogyne enterolobii
Letícia Lopes de Paula, Vicente Paulo Campos, Willian César Terra, Daniele de Brum, Dustin C. Jacobs, Hung Xuan Bui, Johan Desaeger
Abstract
Sustainability can be easily found in a diversified ecosystem, where synergistic interactions among soil microorganisms play a crucial role. Nowadays, numerous microorganisms have been identified as effective agents against plant-parasitic nematodes (PPNs) when applied individually. However, the combination of these known biological agents presents a new perspective for the practical implementation of biological control. In this study, the combination of Purpureocillium lilacinum strain PL251 (Pl) and Bacillus amyloliquefaciens strains D747 (Ba) simultaneously inoculated on cucumber roots, in Florida (USA) soil, significantly reduced (p<0.05) the number of eggs per gram of roots (84%) and gall index compered to negative control. Contrasting with the mixture, the application of each microorganism didn’t show any difference among the negative control. Combined cultures of these microorganisms were also effectiveness on increasing Meloidogyne enterolobii J2 toxicity and inhibit the eggs hatching when tested with cell-free supernatants. Chemotaxis of M. enterolobii J2 showed to be repellent when both microorganisms were placed on the same side of the plate. Also, J2 repellence was obtained when root exudates of cucumber were simultaneously inoculated with both microorganisms. On the other side, the exudates of cucumber roots free of those microorganisms is highly attractive to the J2. Although volatile organic compounds (VOCs) of Ba caused high toxicity to M. enterolobii J2 compared to control, when the combined microorganisms were tested, the effect of VOCs from Ba alone was incredible higher (P<0.05). In fact, in some tests above mentioned, one microorganism alone reached or not the effect of the combination (PL + Ba). The laboratory tests underwent indicated a synergistic effect of the mixture among P. lilacinum and B. amyloliquefaciens explaining the significant effect of both inoculation on the control of the nematode in potted cucumber.