Incorporation of fabaceae biomass into planting substrate for the control of southern blight (Sclerotium rolfsii) in cocona (Solanum sessiliflorum)

Abstract

Cocona (Solanum sessiliflorum Dunal) cultivation in Amazonas State is limited by the high incidence of southern blight (Sclerotium rolfsii Sacc.), and plant material incorporation into the substrate changes the microflora present on it. The objective of this study was to evaluate the control potential of southern blight in cocona by incorporation into the substrate fresh powdered biomass of four Fabaceae species: Erythrina fusca Loureiro and Senna reticulate (Wild.) Irwin & Barneby, which are native to Amazonia, and Desmodium heterocarpon (L.) DC. subsp. ovalifolium (Prain) Ohashi and Gliricidia sepium (Jacq.) Walp, which are exotic. The substrate was infested with 10 g rice colonized with S. rolfsii.L-1 substrate and 40 g biomass of Fabaceae.L--1 substrate were incorporated into 8 L pots, in which cocona seedlings were grown in a nursery. Experimental design was completely randomized, with three replicates and seven treatments (four Fabaceae species and three controls, without biomass incorporation). In one of the controls there was no substrate infestation and in two, the substrate was infested, and in one, the plants were sprayed with fungicide. Another experiment was carried out to evaluate the effect of G. sepium doses incorporated into the substrate. The experiment had a completely randomized design with three replicates and six treatments (40, 80, 120 and 160 g G. sepium.L-1 substrate and two controls without G. sepium incorporation, and one of these controls had its plants treated with fungicide). In both experiments, the disease incidence and inoculum density in the substrate were evaluated. In the first experiment, the data for the area under the disease progress curve were subject to ANOVA and means were compared according to Tukey`s test. In the second experiment, the data were subjected to regression analysis between the levels of biomass incorporated into the substrate. In the first experiment, biomass incorporation did not differ from the fungicide in reducing southern blight incidence and in suppressing the pathogen based on the substrate density. In the second experiment, southern blight incidence reduction was proportional to G. sepium biomass, showing 100% control with the incorporation of 139 g G. sepium.L-1 substrate. The biomass of 142 g reduced S. rolfsii population in the substrate by 20%. © 2019, Universidade Estadual Paulista (UNESP). All rights reserved.