Fusarium solani speciescomplex causing root rot on beans in Brazil

Abstract

Bean Root Rot (BRR) causes considerable losses in the production of pulses, such as common beans and cowpea, which are important elements of the alimentary base of Brazilian people. This disease is caused by members of the Fusarium solani species complex (FSSC), and the name commonly used for the causal agent is F. solani f. sp. phaseoli. In this study, we identified species of the FSSC associated with BRR in common and cowpea beans in Brazil, based on molecular phylogeny of four loci and morphological markers, and also evaluated its pathogenicity to common bean, cowpea, and soybean. A set of 48 isolates was obtained from symptomatic plants, collected in ten states and Federal District. Based on the phylogenetic analyses of partial DNA sequences of rpb2, we identified F. paranaense (n = 35), F. solani (n = 6), F. suttonianum (n = 3) and F. martii (n = 2), all members of Clade 3. Two isolates were identified as members of Clade 2, according to analyses of rpb2, rpb1, tef1, and ITS regions. Representative isolates of the identified species induced BRR symptoms when inoculated in common bean and cowpea. The main symptoms, similar in both plants, consist of rot starting from the main root extending to the hypocotyl, reducing plant growth. Fusarium paranaense, F. solani, F. suttonianum, and F. martii induced root lesions on soybean, while F. martii induced internerval chlorosis. This study clarifies the etiology of BRR based on modern species concepts and will provide relevant support to disease management and plant breeding studies.