RESUMO
In this study, the active metabolites from both the wild strain of Lasiodiplodia pseudotheobromae C1136 and three genetically enhanced strains of C1136 were obtained through random mutagenesis. The effect of the active metabolites from these strains was evaluated in relation to physiological, biochemical, and ultrastructural changes on the leaves of two weeds (Amaranthus hybridus and Echinochloa crus-galli). The phytotoxic metabolites secreted by the genetically enhanced strains showed a decrease in the pigments (chl a, chl b, and carotenoids), carbohydrate content, and the amino acid profile. On the other hand, an increase in total phenols of the tested leaves was observed when compared with the untreated leaves. The scanning electron microscopy showed the presence of damages, necrosis, degradation, and ultrastructural changes on the tested leaf tissues of the weeds. Also, increased lipid peroxidation and electrolyte leakage were also observed on the tested weeds treated with phytotoxic metabolites secreted by the genetically enhanced strains. We also showed that the phytotoxins from the strains of C1136 are biocompatible and that it improved soil CO2 evolution, organic carbon content, and enzymatic activity (acidic and alkaline phosphatase, dehydrogenases, cellulase, catalase). The study validates the severe pathological effects of phytotoxic metabolites from the strains of C1136 on the leaves of the weeds presented in this study. The mode of action of the phytotoxic metabolites produced from this bioherbicidal isolates will go a long way in preventing environmental hazards.