Seleção de genótipos de mandioca resistentes à bacteriose nas condições do semiárido baiano

Abstract

Bacteriosis is considered the main disease of cassava, due to its systemic behavior, which can generate from leaf spots to plant death, preventing a curative treatment, and the use of resistant / tolerant varieties is the most effective control. In this context, this work aims to evaluate the resistance of cassava genotypes to Xanthomonas axonopodis pv. manihotis in the agroecological conditions of the Southwest of Bahia, specifically in the municipality of Guanambi, as well as to evaluate the productivity of these genotypes. The experiment was conducted in Experimental Field I of IFBaiano - Guanambi Campus. The accesses came from the Embrapa Cassava Germplasm Active Bank Mandioca and Fruticultura. The experimental design was randomized blocks with two blocks without inoculation and two blocks with artificial inoculation performed by bacterial cell suspension spraying on the aerial part of the plants at eight months after planting. The evaluation of the symptoms of bacteriosis was performed using a scale of grades varying from 0 to 8 (without symptoms and partial or total death of the plants, respectively). The assigned scores were used to calculate the disease index (ID) and the area under the disease progress curve (AUDPC). Based on the ID and AUDPC values, it was possible to group the genotypes in different classes of resistance / susceptibility, being 15 moderately resistant genotypes, 48 susceptible and 19 extremely susceptible genotypes, with no genotypes with complete resistance to bacteriosis. There was a correlation between the parameters of disease resistance and shoot weight, with no correlation between these parameters and other productivity parameters. There was a correlation between the parameters of disease resistance and shoot weight, with no correlation between these parameters and other productivity parameters. The cultivars BRS Formosa and BRS Caipira and the genotypes BGM0356, BGM1811 and BGM0928 are viable alternatives for planting in regions where there is bacteriose record in the edaphoclimatic conditions of the municipality of Guanambi-BA, as well as presenting moderate resistance to the disease, these reach good productivity