Parâmetros e divergência genética para identificação de acessos de mandioca com resistência à antracnose e bacteriose

Abstract

Anthracnose and bacterial blight are the most important diseases in Brazil in the cassava crop, being the main causes of the losses in the production. One of the reasons is the existence of few control methods, the use of resistant cultivars being the best alternative to reduce losses. The objectives of this study, were to estimate the genetic parameters and through the genetic divergence to perform the identification of accesses that present greater resistance to anthracnose and bacterial blight. The work was carried out at the Fazenda Experimental da Faculdade de Ciências Agrárias da Universidade Federal da Grande Dourados - UFGD, located in the city of Dourados, MS. Three independent experiments were carried out in which 133 accessions from the Embrapa Mandioca and Fruticultura germplasm bank and nine controls were evaluated, distributed in five blocks with five plants per plot in each experiment. The first experiment the plants were inoculated, with the pathogen Xanthomonas axonopodis pv. manihotis (bacterial blight), the second inoculated with Colletotrichum gloeosporioides f. sp. manihotis (anthracnose) and an experiment without inoculation to control, being conducted in the augmented block designs, performing visual evaluations of the plants by scale of notes. By analysis of variance, there was a significant difference for the source of variation of the control experiment, evaluated for Area Under Disease Progress Curve (AUDPC) of anthracnose disease (P≤0.05) and bacterial blight (P≤0.01), which revealed genetic variability between the accesses, with the formation of five groups in the dendrogram obtained by the UPGMA method. Heritability ranged from 38.4% to 92.94%. It was concluded that in the control experiment and for bacteriosis the chance of success in the selection of resistant accessions was higher, and among the groups formed in the dendrogram from genetic divergence, group three formed by two accessions (BGM1170 and BGM1134) was what obtained lower mean for AUDPC.