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

Layla De Sá Andrade Medeiros,Marcelo Eiras,Izaías Araújo De Oliveira,Kedma Da Silva Matos,Elliot Watanabe Kitajima,Simone Graça Ribeiro,Helen Jesus Pereira,José Evando Aguiar Beserra Júnior

doi:10.1590/1678-4499.20190467

Abstract

ABSTRACT 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.

Highlights

Lima bean (Phaseolus lunatus L.) is an annual legume crop of great importance for the food and nutritional security of rural communities in the Northeast region of Brazil due to its good adaptation to the regional climate and soil conditions and its high content of protein (26%), making it an accessible protein source (Barreto Neto et al 2015)
Amplicons were successfully obtained with the set of primers to detect cucumber mosaic virus (CMV), cowpea mild mottle virus (CPMMV), poty- and comovirus in the sampled plants
Sequence analysis of the amplified fragment using primers for poty- and comovirus allowed for the identification of the detected potyvirus as cowpea aphid-borne mosaic virus (CABMV), and the comovirus, as cowpea severe mosaic virus (CPSMV)

Summary

Introduction

Lima bean (Phaseolus lunatus L.) is an annual legume crop of great importance for the food and nutritional security of rural communities in the Northeast region of Brazil due to its good adaptation to the regional climate and soil conditions and its high content of protein (26%), making it an accessible protein source (Barreto Neto et al 2015). Viruses have efficient forms of dissemination, are difficult to control, and are considered a major phytosanitary problem They induce significant yield losses, limiting the production of many economically important crops such as beans (Lima et al 2005). The only comprehensive survey of lima bean viruses in Brazil was carried out for begomoviruses, and two species were identified as causal agents of golden mosaic disease (Ramos Sobrinho et al 2014)

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