Occurrence of Viruses Infecting Yams on Potential Alternative Hosts in Côte d'Ivoire

Abstract

Yam is a crucial crop for food security and income in Côte d'Ivoire. However, its cultivation is threatened by various viral infections that lead to significant yield losses. The spread of these viruses is facilitated by weeds and crops associated with yam, which serve as reservoirs. This study aimed to identify the reservoirs of yam viruses, the prevalence of viruses, and the most widespread plant families hosting yam viruses. In 2019, surveys were conducted in yam fields in six agro-ecological zones (AEZ) of Côte d’Ivoire. A total of 131 symptomatic and asymptomatic leaves from potential yam virus reservoirs were collected and conserved. These samples were screened for Badnaviruses using Immuno-capture PCR (IC-PCR). Potyvirus yamtesselati (yam mosaic virus, YMV), Potyvirus yamplacidum (yam mild mosaic virus, YMMV) and Cucumovirus CMV (cucumber mosaic virus, CMV) were detected using DAS-ELISA and RT- PCR. Eighteen plant families were recorded, the most common of which were Solanaceae, Fabaceae and Poaceae. Additionally, 75.57% of the samples were food crops, while 24.43 % were weeds. Viruses were detected in plants collected in all the six AEZ, and the incidence for at least one virus was 46.56%. CMV (23.66%) is the most widespread in all the zones, followed by Badnaviruses (11.45%) and YMV in only 5.34% of the samples. One case of mixed infection between CMV and Badnaviruses was noticed at the rates of 6.11%. However, no samples were found to be infected by YMMV. Phylogenetic analysis confirmed that Badnaviruses detected in the alternate hosts are yam Badnaviruses. Farmers should be made aware of the threat that could represent these alternative hosts in yam crops, and of the impact of cultural techniques on the occurrence and treatment of viruses.