Molecular Viral Diagnosis and Sanitation of Yam Genetic Resources: Implications for Safe Yam Germplasm Exchange.

Marie Umber,Marie Umber,Séverine Gallet,Denis Filloux,Denis Filloux,Denis Filloux,Denis Filloux,Suzia Gélabale,Armelle Marais,Armelle Marais,Armelle Marais,Claudie Pavis,Séverine Gallet,Pierre-Yves Teycheney,Pierre-Yves Teycheney,Pierre-Yves Teycheney,Suzia Gélabale,Rose-Marie Gomez,Rose-Marie Gomez,Franciane Gamiette,Franciane Gamiette

doi:10.3390/v12101101

Abstract

Yam (Dioscorea spp.) is an important crop in tropical and subtropical regions. Many viruses have been recently identified in yam, hampering genetic conservation and safe international exchanges of yam germplasm. We report on the implementation of reliable and cost-effective PCR-based detection tools targeting eight different yam-infecting viruses. Viral indexing of the in vitro yam collection maintained by the Biological Resources Center for Tropical Plants (BRC-TP) in Guadeloupe (French West Indies) unveiled a high prevalence of potyviruses, badnaviruses, Dioscorea mosaic associated virus (DMaV) and yam asymptomatic virus 1 (YaV1) and a high level of coinfections. Infected yam accessions were subjected to a combination of thermotherapy and meristem culture. Sanitation levels were monitored using PCR-based and high-throughput sequencing-based diagnosis, confirming the efficacy and reliability of PCR-based detection tools. Sanitation rates were highly variable depending on viruses. Sixteen accessions were successfully sanitized, paving the way to safe yam germplasm exchanges and the implementation of clean seed production programs worldwide.

Highlights

Yam is a staple food in the tropics and subtropics and the second most important tuber crop in Africa after cassava
In order to assess the viral status of the Biological Resources Center for Tropical Plants (BRC-TP) in vitro collection, we developed molecular diagnosis tools targeting yam-infecting viruses present in Guadeloupe (Table 1)
This paper reports on the development and optimization of diagnostic tools for the detection of viruses infecting yams and their successful implementation for the sanitation of yam accessions, resulting in virus-free yam germplasm and paving the way to a better control of yam-infecting viruses

Summary

Introduction

Yam is a staple food in the tropics and subtropics and the second most important tuber crop in Africa after cassava. Annual worldwide yam production was 73 million tons in 2018, with five. Worldwide yam production is increasing, yields are declining in some areas mostly due to decreasing soil fertility or attacks by pests and pathogens. In Guadeloupe (French West Indies), yam production has decreased by almost two thirds in 20 years, from 9000 t in 1997 to 3425 t in 2018 [1]. Guadeloupe is no longer self-sufficient and must import 80% of its yam tuber consumption needs. This steep decrease results from a combination of socio-economic and health factors such as the decrease of available cultivable lands, the increase in labor costs and the spread of pests and pathogens [2], especially viruses.

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Conclusion