Plant-Parasitic Nematodes Associated with Rice (Oryza spp.) and their Relationship with Rice Ecosystems in Côte d’Ivoire

Rice is a staple crop in Africa, especially in Côte d’Ivoire. Its production is threatened by plant-parasitic nematodes, which cause root damage, stunted growth, and yield loss. This study aimed to identify nematode populations associated with rice and determine their distribution across rice ecosystems to prioritize management measures to secure rice production. Surveys were conducted in 27 rice fields within three agroecological zones in Côte d’Ivoire. A total of 185 soil and rice root samples were collected. The nematodes in these samples were extracted, identified, and counted. Ten genera of plant-parasitic nematodes were identified. The most prevalent nematode, with 100% occurrence, included Pratylenchus, Hirschmanniella, Heterodera, Meloidogyne, and Longidorus. Pratylenchus sp. Hirschmaniella sp. Heterodera sp. were the most abundant in rice fields in the southern dense rainforest zone, with densities ranging from 292 to 1756 individuals per 5g roots. However, Hirschmaniella sp. was the most abundant nematode (150 individuals/5g roots) in rice fields from the western dense rainforest zone. From the semi-deciduous dense rainforest zone side, Pratylenchus sp. Hirschmaniella sp. and Meloidogyne sp. were the most abundant nematodes, with densities ranging from 114 to 1072 individuals per 5g roots. They were abundant in upland rice samples (39 to 1748 individuals/5g roots) and lowland rice samples (75 to 1367 individuals/5g roots). Pratylenchus sp., Hirschmanniella sp., and Meloidogyne sp. were associated with upland rice, while Heterodera sp. and Longidorus sp. were linked to lowland and irrigated rice, respectively. Further molecular and pathological characterizations of these nematode populations are necessary to develop effective management strategies for the most pathogenic ones in rice.