Potential weeds host-reservoirs of Rice Yellow Mottle Virus in irrigated rice fields of Niger

Rice Yellow Mottle Virus (RYMV) is spread in the field by insect vectors and weeds. The study contributes to the fight against the spread of the virus. It consisted in collecting and characterizing the weeds present in and around the rice fields and then carrying out a survey followed by field visits to 81 farmers in the target areas. In total, seventy-five (75) species of rice weeds were inventoried. They belong to Grass family (28 species), Cyperaceae family (10 species) and 21 other broad-leaved herbaceous families (37 species). Among these weeds, Rotala indica, Cyperus spp and Echinochloa spp are the most widely recognized, frequent and damaging to rice, while most growers are less familiar with Oryza barthii, Leersia Oryzoides and Nymphea tetragonal. In terms of biological characteristics, twelve (12) weed species were found to be potential host-reservoirs for RYMV. They mainly belong to Grass (7 species) and Cyperaceae (5 species) families. The Grass species are Echinochloa colona, Cynodon dactylon, Echinochloa crus-galii, Leersia hexandra, Leersia oryzoides, Panicum repens and Paspalum scorbilatum when Cyperaceae’s especies include Cyperus difformis, Cyperus esculentus, Cyperus iria, Cyperus distans and Pycrerus lanceolatus. The frequency of RYMV weed hosts-reservoirs varies from family and plot. Grasses (58.33%) predominate over Cyperaceae (41.67%). Cynedon dactylon is the most widespread species, followed by Echinochloa colona which is more difficult to control. Among the Cyperaceae, Cyperus difformis is the most common weed and the most difficult to control. Based on farmers weed control, weeding and/or the application of synthetic herbicides have proved more effective. These results would help to control RYMV and it’s spread in African rice-growing ecologies.