Desenvolvimento de bioformulações contendo endósporos de Bacillus velezensis S26 para controle biológico de doenças e promoção do crescimento vegetal

Abstract

The bioinputs has gained prominence in response to the harmful effects caused by synthetic fertilizers and pesticides on the environment and human health. The genus Bacillus consists of Gram-positive, endospore-forming bacteria with antagonistic potential against various phytopathogens. These bacteria also stimulate plant development and induce resistance mechanisms in plants. Consequently, the use of endospores can contribute to extending the shelf life and stability of bioformulations. This study aimed to determine the inhibitory potential of Bacillus velezensis S26 endospores suspensions in controlling gray mold caused by Botrytis spp., anthracnose caused by Colletotrichum spp., and black foot rot, with the causal agent being the fungus Dactylonectria macrodidyma. Additionally, the study sought to investigate the action of B. velezensis S26 endospores suspensions in promoting the growth of strawberries and grapevines and to develop liquid and dry formulations using agro-industrial by-products. Initially, trials were conducted to induce and optimize bacterial sporulation in shaking-flasks. Subsequently, the antagonistic potential of B. velezensis S26 endospore suspensions against isolates of Botrytis spp. and Colletotrichum spp. was evaluated both in vitro and in vivo. In vivo trials were conducted on fruits and plants of grapevine and strawberry under controlled environmental conditions. Four bioformulations were then developed, consisting of leachate from grape marc composting and whey, either individually or in combination. The effectiveness of these formulations was determined under controlled conditions and in a commercial strawberry greenhouse. Similarly, a dry formulation was developed from two biochars derived from the pyrolysis of fresh grape pomace and previously composted grape pomace. The growthpromoting potential of these formulations was tested on the grapevine rootstock SO4 (Vitis berlandieri × V. riparia), cultivated in conventional substrate and copper-treated substrate. The effect of biochars associated with B. velezensis S26 endospores on black foot rot suppression was also examined. The results demonstrated that B. velezensis S26 endospores can effectively control anthracnose and gray mold in strawberries and grapevines. This inhibitory capacity was maintained even after six months of storage. Furthermore, cultivation in shaking-flasks and bioreactors led to B. velezensis S26 sporulation using compost leachate and whey as culture media. The use of these culture suspensions as liquid formulations provided performance similar to the commercial bioproduct Duravel WP® in a commercial strawberry greenhouse and promoted the growth of micropropagated strawberry plants. Finally, treatments using biochar enriched with B. velezensis S26 endospores contributed to minimize copper-induced stress, increase the biomass of micropropagated SO4 plants, and control grapevine black foot rot. Therefore, B. velezensis S26 emerges as a promising agent in the biocontrol of anthracnose, gray mold, and black foot rot, not only reducing the incidence and severity of these diseases but also stimulating the growth of these plants. As a result, the incorporation of B. velezensis S26 endospores into liquid bioformulations and biochars allows for the preservation of both cellular viability during storage and the ability to suppress fungal diseases and stimulate plant development, contributing to sustainable agriculture and adding value to agro-industrial waste and by-products. [resumo fornecido pelo autor]