Variation for pathogenicity among isolates of bean common mosaic virus in Africa and a reinterpretation of the genetic relationship between cultivars of Phaseolus vulgaris and pathotypes of BCMV

Abstract

Bean common mosaic virus (BCMV) isolates were collected from crops of Phaseolus vulgaris (bean) and from wild legume species in 13 African countries. Isolates of pathotype VIa from both beans and wild legume species were predominant in central, eastern and southern Africa. Isolates of pathotypes I, III, IVa, IVb and Va were also found. Some isolates did not conform to previously published pathotypes, and therefore represent records of novel pathotypes. The susceptibility of various wild legume species to BCMV was investigated and isolates of the virus obtained from Crotalaria incana, Rhynchosia sp., Macroptilium atropurpureum and Cassia occidentalis (synonym Senna occidentalis) were aphid‐transmitted both from P. vulgaris to their original host species and to P. vulgaris. Isolates of BCMV from wild legume species were seed‐transmitted in bean and in several other legume species. The natural occurrence of BCMV in wild legume species in Africa is probably a significant factor in the ecology and epidemiology of the virus and possibly the evolution of isolates of the ‘A’ serotype which induce necrotic reactions in cultivars carrying the I gene for resistance. The occurrence of viruses other than BCMV from P. vulgaris and other legume hosts is also reported. The gene‐for‐gene model described by Drijfhout (1978) is reinterpreted to explain the variation for pathogenicity, and it is proposed that there may be genes which control the temperature sensitivity of necrosis in combination with the I gene.

Viruses infecting common bean (Phaseolus vulgaris L.) in Tanzania: A review on molecular characterization, detection and disease management options

“…An additional short open reading frame known as Pretty Interesting Potyviridae ORF (PIPO) has been described in the P3 cistron (Chung et al, 2008). BCMV and BCMNV are transmitted in common bean seeds by several aphids in a non-persistent manner (Spence and Walkey, 1995). Aspects of taxonomy and transmission of these viruses were recently reviewed (Worrall et al, 2015) and are beyond the scope of this review.…”

Markers linked to the bc-3 gene conditioning resistance to bean common mosaic potyviruses in common bean

“…Both viruses are seedborne and transmitted by several aphid species in a non-persistent manner (Drijfhout, 1978). These viruses have been reported in common bean in many parts of the world including Europe (Drijfhout, 1978;Sáiz et al, 1995), U.S. (Kelly et al, 1983;Provvidenti et al, 1984), Canada (Tu, 1986), Mexico (Flores-Estévez et al, 2003) and Africa (Silbernagel et al, 1986;Spence & Walkey, 1995;Sengooba et al, 1997;Njau & Lyimo, 2000). BCMNV likely evolved more recently in the African continent (Spence & Walkey, 1995) and recombination has been observed between strains of BCMV and BCMNV (Silbernagel et al, 2001).…”

“…Among the methods available to prevent virus infection in common bean, genetic resistance is the most cost effective and durable (Drijfhout, 1978;Kelly et al, 1995;Miklas et al, 2000). In East Africa where BCMNV is found in wild legumes (Sengooba et al, 1997;Spence & Walkey, 1995), the only effective way to control these viruses is to plant resistant cultivars, otherwise susceptible bean plants can become infected from alternate hosts, growing adjacent to bean fields .…”

Analysis of 3′-Terminal Region of Bean common mosaic virus Strains Infecting Common Bean in India

“…The coding ORF is translated into one polyprotein of 340-370 Da which is processed into proteinase (Pro-1), helper component proteinase (HcPro), proteinase (Pro-3), a 6 kDa protein, cylindrical inclusion (CI), a second 6 kDa protein product, nuclear inclusion a (NIa), nuclear inclusion b (NIb) and CP [8]. BCMV is known to possess high pathogenic variability in Europe, USA and Africa, and virus strains have been identified on bean differentials [6,7,12,19,22,28]. There are reports of BCMV occurrence on common bean in India and BCMV recurs regularly in this region with an incidence ranging from 0.5 to 77.0 per cent causing economic losses [23].…”