Bacillus subtilis e abamectina no controle de Rotylenchulus reniformis e Pratylenchus brachyurus e alterações fisiológicas em algodoeiro em condições controladas

Abstract

The aim of this study was to evaluate the effects of cotton seed treatments with Bacillus subtilis and a chemical nematicide (abamectin) on plant development in soils infested with nematodes. For this, the cotton genotypes IAC 25, Deltaopal and Nuopal were cultivated in ceramic pots with 10 kg of soil in a greenhouse. The soils samples were collected from areas under cotton cultivation in western Bahia State infested with Pratylenchus brachyurus and Rotylenchulus reniformis. To evaluate the efficiency of biological control of nematodes with B. subtilis, a previous inoculation of the cotton seeds at the date planting was made comparatively to the reference the application of the nematicide abamectin (AVICTA 500 FS®) in the seeds. After 45 days of cultivation leaf samples were collected for proline and peroxidase analyzes in all treatments. The plants were analyzed 60 days after planting for active nematodes in the root and in the soil. The most susceptible genotype (Deltaopal) showed higher proline content in their leaves. The hypothesis that the B. subtilis could act effectively in the control of the nematodes R. reniformis and P. brachyurus in cotton plants was confirmed in this study. It was also observed that the treatment of cotton seeds with B. subtilis was as efficient as the treatment with the chemical nematicide abamectin. The cotton genotypes responded differently to the chemical and biological control treatments. The effects of the both seed treatments on the reduction of the nematodes and on the plant growth were more pronounced in the soils with higher infestation.