Identificação de fontes de resistência e espécies de fungos e oomicetos causadores de podridão radicular em mandioca

Abstract

Root rot is one of the most important diseases in cassava (Manihot esculenta Crantz) in Brazil, which can lead to total crop failure. However, there is not a detailed description of species associated to root rot and its distribution throughout the country. As a control measure, the use of resistant varieties is currently the most economically viable approach. This work aimed to characterize the pathogens that cause cassava root rot disease in different producing regions in Brazil and select resistant genotypes. 74 isolates associated to cassava root rot from different producing regions in Brazil were analyzed. The isolates were classified in species from different genus, such as Fusarium (75,68%), Lasiodiplodia (10,81%), Neoscytalidium (8,11%), Phomopsis (1,35%), Diaporthe (1,35%), Phytophthora (1,35%) and Nectria (1,35%) genera. Inoculations with Fusarium spp. (Fspp) were carried out in 697 accessions to evaluate symptom severity in the bark (cortex and periderm) and root pulp. Approximately 10% of the accessions were classified as resistant (R), 50% as moderately resistant (MR), 28% as moderately susceptible (MS), 10% as susceptible (S) and 2% as highly susceptible (HS). Cassava root rot takes place due to the attack of more than one species, even in the same region. Knowing the main pathogens causing cassava root rot and the selection of resistant accessions can direct the researches in obtaining a more endurable genetic resistance.