Cowpea mild mottle virus ( Carlavirus, Betaflexiviridae ): a review

In this review we describe and discuss the biology and aspects of infection of a pathogen, the RNA virus Cowpea mild mottle virus (CPMMV), that emerged as a problem in soybean and is re-emerging in common bean. The review takes a global perspective but has an emphasis on Brazilian soybean in which CPMMV causes stem necrosis. Since its first description in Ghana in 1973, CPMMV has spread across the world and, although it principally infects Fabaceae, it is also able to infect hosts from Solanaceae and Lamiaceae. While the problem in soybean is being tackled with resistant varieties, CPMMV is re-emerging in genetically modified common bean. To limit the impact of CPMMV and combat future outbreaks, it is necessary to understand the ecological and evolutionary factors that influence its emergence. We identify surveillance as a key defense against CPMMV, as CPMMV is transmitted non-persistently by the whitefly Bemisia tabaci , there is the possibility of seed transmission and the virus is able to cause asymptomatic infections. We discuss the potential for development of resistant crop lines and identify key areas for future research.