Bioprospecção de actinobactérias isoladas do mangue para biocontrole de Corynespora cassiicola

Abstract

The soybean productivity faces significant threats, such as target spot caused by the pathogen Corynespora cassiicola. Biological control, through bioprospecting in biomes with high biotechnological potential, such as mangroves, emerges as an alternative for disease management. In this context, actinobacteria from this biome represent a promising group for the development of new biofungicides. In thin study, 92 actinobacteria were isolated from mangrove sediment samples from the Cananéia region, São Paulo, Brazil. The isolates were morphologically selected and evaluated for their in vitro control potential against the phytopathogens Corynespora cassiicola, Colletotrichum truncatum, Macrophomina phaseolina, Rhizoctonia solani, and Sclerotinia sclerotiorum. Three isolates (MG04, MG26, and MG69) exhibited antifungal activity against all tested phytopathogens and were selected for characterization regarding the production of lytic enzymes (chitinase and β-1,3-glucanase), indole-3-acetic acid (IAA), siderophores, inorganic phosphate solubilization, and their potential for in vivo control of C. cassiicola in soybean, compared to the actinobacterium Streptomyces sp. ACTR8, a reference strain from Agrivalle Brasil’s culture collection. All isolates tested positive to produce lytic enzymes, IAA, and siderophores, but none were positive for phosphate solubilization. Isolates MG04 and MG26 stood out in chitinase production, while none showed outstanding β-1,3-glucanase production. Isolate MG26 also exhibited high IAA production, whereas Streptomyces sp. ACTR8 stood out for siderophore production. In the in vivo target spot control assay, all treatments demonstrated significant control efficiency, except for isolate MG69. Isolates MG04 and MG26 showed target spot control efficiency statistically similar to the commercial biofungicide Twixx-A (Agrivalle). The genome of isolate MG04 was sequenced, assembled, and annotated. Genomic metric analyses demonstrated that the MG04 genome formed a statistically supported clade in the phylogenomic analysis with S. solisilvae HNM0141. The genome mining strategy allowed the identification of gene clusters with compounds previously reported for biological activity against phytopathogens. The development of bioinputs based on Streptomyces solisilvae MG04 requires characterization of the active ingredient, optimization of bioprocesses for spore or metabolite production, formulation development, and agronomic validation under different agricultural conditions. For target spot management, it is essential to evaluate integration with chemical fungicides and potential applications across various crops and agricultural systems.