Abstract
Viral diseases are a major threat for common bean production. According to recent surveys, >15 different viruses belonging to 11 genera were shown to infect common bean (Phaseolus vulgaris L.) in Tanzania. Virus management requires an understanding of how viruses survive from one season to the next. During this study, we explored the possibility that alternative host plants have a central role in the survival of common bean viruses. We used next-generation sequencing (NGS) techniques to sequence virus-derived small interfering RNAs together with conventional reverse-transcription PCRs (RT-PCRs) to detect viruses in wild plants. Leaf samples for RNA extraction and NGS were collected from 1,430 wild plants around and within common bean fields in four agricultural zones in Tanzania. At least partial genome sequences of viruses potentially belonging to 25 genera were detected. The greatest virus diversity was detected in the eastern and northern zones, whereas wild plants in the Lake zone and especially in the southern highlands zone showed only a few viruses. The RT-PCR analysis of all collected plant samples confirmed the presence of yam bean mosaic virus and peanut mottle virus in wild legume plants. Of all viruses detected, only two viruses, cucumber mosaic virus and a novel bromovirus related to cowpea chlorotic mottle virus and brome mosaic virus, were mechanically transmitted from wild plants to common bean plants. The data generated during this study are crucial for the development of viral disease management strategies and predicting crop viral disease outbreaks in different agricultural regions in Tanzania and beyond.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
Highlights
Viruses are obligate parasites that are dependent on their hosts; viruses that infect annual crop plants require alternate hosts for their survival during the offseason
A recent comprehensive survey of common bean viruses revealed that >15 viruses belonging to 11 genera infect common bean in Tanzania (Mwaipopo et al 2018)
Because seed transmission of these pathogenic viruses to P. vulgaris, an annual crop, is not common (Nordenstedt et al 2017), it is likely that the viruses are surviving in alternative host plants from which they are transmitted to common bean plants when they are grown in proximity
Summary
Viruses are obligate parasites that are dependent on their hosts; viruses that infect annual crop plants require alternate hosts for their survival during the offseason. Many studies have explored the occurrence of viruses in wild plants and their transmission to the crops of economic importance in which they cause diseases (Njau and Lyimo 2000; Prendeville et al 2012; Susi et al 2019; Tugume et al 2008). Viruses have been detected using enzyme-linked immunosorbent assays (ELISA) and/ or reverse-transcription polymerase chain reaction (RT-PCR); RT-PCR is more sensitive than ELISA. Because most of these studies have relied on ELISA, it is likely that the number of viruses detected in wild plants has been largely underestimated
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