Host range and molecular variability of the sadwavirus dioscorea mosaic associated virus

Molecular diversity of yam virus Y and identification of banana mild mosaic virus isolates infecting yam (Dioscorea spp.)

Two members of the family Betaflexiviridae associated with yam (Dioscorea spp.) have been described so far: yam latent virus (YLV) and yam virus Y (YVY). However, their geographical distribution and molecular diversity remain poorly documented. Using a nested RT-PCR assay, we detected YVY in D. alata, D. bulbifera, D. cayenensis, D. rotundata, and D. trifida in Guadeloupe, and in D. rotundata in Côte d'Ivoire, thus extending the known host range of this virus and geographical distribution. Using amplicon sequencing, we determined that the molecular diversity of YVY in the yam samples analyzed in this work ranged between 0.0 and 29.1% and that this diversity is partially geographically structured. We also identified three isolates of banana mild mosaic virus (BanMMV) infecting D. alata in Guadeloupe, providing the first evidence for BanMMV infection in yam.

Epidemiology of Yam Viruses in Guadeloupe: Role of Cropping Practices and Seed-Tuber Supply

The epidemiology of yam viruses remains largely unexplored. We present a large-scale epidemiological study of yam viruses in Guadeloupe based on the analysis of 1124 leaf samples collected from yams and weeds. We addressed the prevalence of cucumber mosaic virus (CMV), Cordyline virus 1 (CoV1), Dioscorea mosaic associated virus (DMaV), yam asymptomatic virus 1 (YaV1), yam mosaic virus (YMV), yam mild mosaic virus (YMMV), badnaviruses, macluraviruses and potexviruses, and the key epidemiological drivers of these viruses. We provide evidence that several weeds are reservoirs of YMMV and that YMMV isolates infecting weeds cluster together with those infecting yams, pointing to the role of weeds in the epidemiology of YMMV. We report the occurrence of yam chlorotic necrosis virus (YCNV) in Guadeloupe, the introduction of YMMV isolates through the importation of yam tubers, and the absence of vertical transmission of YaV1. We identified specific effects on some cropping practices, such as weed management and the use of chemical pesticides, on the occurrence of a few viruses, but no crop-related factor had a strong or general effect on the overall epidemiology of the targeted viruses. Overall, our work provides insights into the epidemiology of yam viruses that will help design more efficient control strategies.

Viruses of Yams (Dioscorea spp.): Current Gaps in Knowledge and Future Research Directions to Improve Disease Management

Viruses are a major constraint for yam production worldwide. They hamper the conservation, movement, and exchange of yam germplasm and are a threat to food security in tropical and subtropical areas of Africa and the Pacific where yam is a staple food and a source of income. However, the biology and impact of yam viruses remains largely unknown. This review summarizes current knowledge on yam viruses and emphasizes gaps that exist in the knowledge of the biology of these viruses, their diagnosis, and their impact on production. It provides essential information to inform the implementation of more effective virus control strategies.