# Epidemiology of yam viruses: spatial monitoring and dynamics of recontamination of sanitized plants under field conditions in Guadeloupe

Mame Boucar Diouf, Eric Francius, Sébastien Guyader, Pierre-Yves Teycheney, Marie Umber

<figure><img src="image_1.png" /></figure>

## To cite this version:

Mame Boucar Diouf, Eric Francius, Sébastien Guyader, Pierre-Yves Teycheney, Marie Umber. Epidemiology of yam viruses: spatial monitoring and dynamics of recontamination of sanitized plants under field conditions in Guadeloupe. 18e Rencontres de Virologie Végétale (RVV 2021), Sep 2021, Aussois, France. hal-03366099

HAL Id: hal-03366099

https://hal.inrae.fr/hal-03366099v1

Submitted on 27 Sep 2024

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

<figure><img src="image_2.png" /></figure>
<figure><img src="image_3.png" /></figure>

# Epidemiology of yam viruses: spatial monitoring and dynamics of recontamination of sanitized plants under field conditions in Guadeloupe

Mame Boucar Diouf ¹²³, Eric Francius <fnref n="1" />, Sébastien Guyader <fnref n="1" />, Pierre-Yves Teycheney ²³, Marie Umber <fnref n="1" />

<footnote n="1">¹ INRAE, UR ASTRO, F-97170, Petit-Bourg, Guadeloupe, France - Mame-boucar.diouf@inrae.fr</footnote>

<footnote n="2">² CIRAD, UMR AGAP, F-97130, Capesterre Belle-Eau, Guadeloupe, France;</footnote>

<footnote n="3">³ UMR AGAP Institut, Univ Montpellier, CIRAD, INRAE, Institut Agro, F-97130 Capesterre Belle Eau, France</footnote>
> Yams worldwide

A staple food for 300 million people

Food security

<figure><img src="image_4.png" /></figure>

Cultural value

> Yams in Guadeloupe

<figure><img src="image_5.png" /></figure>

Source: FAOSTAT (juin 22, 2021)

Steep decrease of the production results from the spread of viral diseases and changes in land use.
-> production does not cover local needs anymore.
> Objectives of the work

To provide the actors of the
sector with healthy plant
material.

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /></figure>

Biology and epidemiology of these new viral species are still unknown.

<figure><img src="image_9.png" /></figure>

1. Study the prevalence and diversity of yam viruses in Guadeloupe.

2. Assess the role of reservoir plants and cultural practices in the epidemiology of yam viruses.

3. Assess the dynamics of viral recontamination of sanitized plants in the field.

-> Implementation of adapted strategies to limit the impact of viruses on yam production in Guadeloupe, restore production and increase self sufficiency.

->Rationalization of the BRC-TP sanitation program.
## 1. Prevalence and diversity of yam viruses in Guadeloupe

### 2019-2020 PREV

* 18 plots sampled (8 GT, 6 BT and 4 MG), representing the diversity of cultivation conditions and practices

* 782 yam leaf samples collected: 6 yam species, 15 varieties

* 46 leaf samples from weeds

### 2020-2021 DIV

* 2 plots sampled (Petit Canal & Roujol)

* 117 yam leaf samples collected: 1 species, 7 varieties

* 85 leaf samples from weeds

+393 leaf samples from the yam *in vitro* collection of BRC-TP, 10 species

Basse-Terre

Grande-Terre

Marie Galante

Each sample indexed for all 9 RNA viruses previously reported in Guadeloupe
> 1. Prevalence and diversity of yam viruses in Guadeloupe

See poster
P26

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /></figure>
> 1. Prevalence and diversity of yam viruses in Guadeloupe

<figure><img src="image_12.png" /></figure>

Only 1% of the plants tested were healthy.
Single infections occur in only 30% of the samples.
## 2. Role of reservoir plants and cultural practices in the epidemiology of yam viruses.

### Methods : Variables analyzed by the PCA

- origin of seeds

- Adjacent crops

- previous crops on the plot

- Number of varieties

- Farming practices : ploughing, staking, weeding, amendment, phytosanitary product

PCA analysis

<figure><img src="image_13.png" /></figure>

<figure><img src="image_14.png" /></figure>

The epidemiological situation cannot be explained by farming practices nor geographical location
> 2. Role of reservoir plants and cultural practices in the epidemiology of yam viruses.

Diapo à compléter avec séq
2 autres PL adventices +
cabusah Costa Rica

<figure><img src="image_15.png" /><figcaption>Cleome viscosa</figcaption></figure>

<figure><img src="image_16.png" /></figure>
## 3. Dynamics of viral recontamination of sanitized plants in the field

<figure><img src="image_17.png" /></figure>

60d
Time 1

120d
Time 2

180d
Time 3

Days after
weaning.

30d
Time 1

90d
Time 2

180d
Time 3

Days after
germination.

Same kinetics as year 2
## 3. Dynamics of viral recontamination of sanitized plants in the field

<figure><img src="image_18.png" /></figure>

<figure><img src="image_19.png" /></figure>

<figure><img src="image_20.png" /></figure>

<figure><img src="image_21.png" /></figure>
## 3. Dynamics of viral recontamination of sanitized plants in the field

<figure><img src="image_22.png" /></figure>

<figure><img src="image_23.png" /></figure>

<figure><img src="image_24.png" /></figure>

<figure><img src="image_25.png" /></figure>
## 3. Dynamics of viral recontamination of sanitized plants in the field

<table><tr><td></td><td>Planting</td><td>30<br>T1</td><td>90<br>T2</td><td>180<br>T3</td><td>Days after<br>germination</td></tr><tr><td>T0</td><td>↓</td><td></td><td></td><td></td><td></td></tr></table>

<figure><img src="image_26.png" /></figure>

<figure><img src="image_27.png" /></figure>

<figure><img src="image_28.png" /></figure>
> CONCLUSION

1. Prevalence and diversity of yam viruses in Guadeloupe

-> Only 1% of the plants tested were healthy.

-> With 69% of plants showing coinfection, we can consider virus coinfection as the rule on yam.

-> Fairly homogeneous distribution of viruses between the three yam production areas

2. Role of reservoir plants and cultural practices in the epidemiology of yam viruses.

-> No cultivation practice sufficiently discriminating to explain the distribution of yam viruses in Guadeloupe.

->Identification of YMMV on imported yams and weeds shows the importance of seed origin and good weed management to limit viral diseases on yam.

-> During the non-crop period, weeds can act as reservoirs for YMMV and promote secondary spread by insect vectors during the crop period.

3. Dynamics of viral recontamination of sanitized plants in the field

-> YMMV and YaV1 were the only viruses found out of the 9 tested, which is consistent with the prevalence observed at the territory scale.

-> The fact that the most damaging viruses (YMV, YVX) were not found in the first year of field trials is very encouraging for the yam sector in Guadeloupe

-> Rapid recontamination by YMMV and YaV1 of healthy plants suggests significant vector transmission.

-> The different patterns of recontamination by these two viruses suggest different types of vectors.

► Viral metagenomics to complete the puzzle

► Study the parameters related to the transmission of these viruses.

► The data acquired ----> model the epidemiology of yam viruses ----> propose control methods adapted to Guadeloupe.

► Rationalisation of the BRC-TP sanitation programme
> Acknowlegment

INRAE and CIRAD as well as their partners in Guadeloupe
who allowed the financing of this thesis.

Marie Umber, Teycheney, Sébastien Guyader, Eric Francius,
Levy Laurent, Lucien Monpierre, Rose-Marie Gomez, Yoana
Faure, Gersende Pressat, David Mathias, Claire Million-
Ranquin, Alisson Abadie, Nolan Pellucier, Olyvia Gaspard
and the farmers.

INRAE

<figure><img src="image_29.png" /></figure>

cirad
LA RECHERCHE AGRONOMIQUE
POUR LE DÉVELOPPEMENT

<figure><img src="image_30.png" /></figure>

malin

maladies infectieuses en milieu insulaire tropical

<figure><img src="image_31.png" /></figure>

<figure><img src="image_32.png" /></figure>

<figure><img src="image_33.png" /></figure>

UNION EUROPÉENNE

PROJET COFINANCE
par le fonds européen
de développement régional

RITA
GUADELOUPE

Réseau d'innovation
et de transfert agricole

<figure><img src="image_34.png" /></figure>

INRAE