Controle biológico de Pratylenchus brachyurus em soja via tratamento de sementes

Abstract

Soybean (Glycine max L.) is the most widely produced grain in Brazil under extensive cultivation. However, its productivity can be impaired when pathogens, such as the root lesion nematode Pratylenchus brachyurus, are present in its root system. Due to the difficulty in controlling this pathogen, alternative methods have been studied, such as biological control using fungi and bacteria. The objective of this study was to evaluate the effect of biological products in the control of P. brachyurus in soybean. The seeds were treated with Bacillus firmus, Bacillus amyloliquefaciens, Trichoderma harzianum, Purpureocillium lilacinum and Pochonia chlamydosporia, in addition to the untreated control. In vitro experiments were performed to evaluate the mortality of P. brachyurus and in vivo experiments to evaluate the agronomic variables (root length, root volume, fresh root mass, dry mass of the aerial part) and nematological variables (number of nematodes in the root and in the soil). The latter was performed in two different growing seasons. All experiments had five replicates and followed the manufacturer's recommendations. In the in vivo assay, inoculation was performed at the time of sowing, with the inoculum consisting of 500 specimens of P. brachyurus per pot. The biological agents acted as nematicide in the in vitro experiment. In the in vivo assays, the results indicated significance of the treatments only for dry mass of the aerial part, number of nematodes in the soil and number of nematodes in the root. In the soil, the reduction ranged from 48% to 88%, while in the root, the reduction was between 49% and 84% in the number of nematodes. Thus, the tested products have potential for controlling P. brachyurus in soybeans via seed treatment.