The complex interactions of common bean (Phaseolus vulgaris 2 L.) with viruses, vectors and beneficial organisms in the context 3 of sub-Saharan Africa

Abstract

Common bean (Phaseolus vulgaris L.), the world’s most widely grown legume 14 crop, is not only of great commercial importance but is also a vital smallholder crop in 15 low-to-medium-income countries. In sub-Saharan Africa common bean provides 16 consumers with a major proportion of their dietary protein and micronutrients. However, 17 productivity is constrained by viruses, particularly those vectored by aphids and 18 whiteflies, and problems are further compounded by seed-borne transmission. We 19 describe common bean’s major viral threats including the aphid-transmitted RNA viruses 20 bean common mosaic virus and bean common mosaic necrosis virus, and the whitefly-21 transmitted begomoviruses bean golden mosaic virus and bean golden yellow mosaic 22 virus and discuss how high-throughput sequencing is revealing emerging threats. We 23 discuss how recent work on indirect and direct viral ‘manipulation’ of vector behaviour 24 is influencing modelling of viral epidemics. Viral extended phenotypes also modify 25 legume interactions with beneficial organisms including root-associated microbes, 26 pollinators and the natural enemies of vectors. While problems with common bean tissue 27 culture have constrained transgenic and gene editing approaches to crop protection, 28 topical application of double-stranded RNA molecules could provide a practical 29 protection system compatible with the wide diversity of common bean lines grown in sub-30 Saharan Africa.