A survey of RNA genome viruses in Lima bean crops of Northeastern Brazil

Lima bean plants showing mosaic and leaf distortion symptoms, similar to those induced by viruses, were observed in several production areas in the states of Ceara and Piaui, Northeastern Brazil. The aim of this study was to identify RNA genome viruses that infect lima bean. Field research was conducted from 2017 to 2018. Fifty-five symptomatic samples were randomly collected from seven properties in five municipalities and tested by RT-PCR and DNA sequencing with specific or universal primers for two viruses and two virus groups. Four virus species were identified: cucumber mosaic virus (CMV), cowpea mild mottle virus (CPMMV), cowpea aphid-borne mosaic virus (CABMV) and cowpea severe mosaic virus (CPSMV), which had infection levels of 21.8, 52.7, 47.2, and 1.8%, respectively, as well as double and triple infections. The CMV isolates belonged to subgroup IA. The CPMMV isolates had high nucleotide identity with CPMMV isolates from Brazil, USA and Mexico. The CABMV isolates showed moderate nucleotide identity with Brazilian isolates. Only one sample was infected with CPSMV. This is the first record of CPMMV and CPSMV naturally infecting lima bean. Approaches to virus control are discussed.