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International audience; By ingesting soil and organic matter in different soil horizons and depositing casts on soil surface, anecic earthworms have large influence on soil ecological processes. However, we still have a limited understanding of the consequences of earthworm casting activity on nematode communities, and the role played by the land use in this relationship. Therefore, the main objective of this study was to compare the effect of the anecic earthworm Amynthas adexilis (Thai, 1984) on the structure of nematode communities, in a woodland and meadow presenting different soil organic C content in northern Vietnam. Nematode population and physico-chemical properties of casts produced by the anecic earthworm A. adexilis and adjacent soil presenting no recent earthworm activity (0-10cm deep) were characterized. A. adexilis incorporated organic matter into its casts compared to the adjacent bulk top soil horizon, reflected by a significant increase of the organic carbon and nitrogen contents (1.4 times more in the meadow and 1.8 times more in the woodland). Earthworm casts contained 2.6 and 1.7 times more nematodes than the adjacent top soil, in meadow and woodland, respectively. The effect of earthworm casting activity on nematode community structure was similar in both land uses. Compared to the soil, casts were significantly enriched in all trophic groups (between 1.9 and 11.6 times more in casts in the meadow, and between 1.6 and 23.7 times more in casts in the woodland, depending on the trophic group), except for obligate plant feeders that were under-represented (1.4 times less in casts for both land uses). The plant parasitic index decreased in the casts compared to the soil, indicating an environment less favourable for plant parasitic nematodes.

Rice yellow mottle virus in Senegal is reported here for the first time. The near-complete genomic sequences of two isolates (Se1 and Se5) were obtained. A comparison with 18 sequences from West Africa revealed a new cluster with an isolate from Gambia, located at a basal position in the phylogenetic tree.

Meloidogyne graminicola is a facultative meiotic parthenogenetic root-knot nematode (RKN) that seriously threatens agriculture worldwide. We have little understanding of its origin, genomic structure, and intraspecific diversity. Such information would offer better knowledge of how this nematode successfully damages rice in many different environments. Previous studies on nuclear ribosomal DNA (nrDNA) suggested a close phylogenetic relationship between M. graminicola and Meloidogyne oryzae, despite their different modes of reproduction and geographical distribution. In order to clarify the evolutionary history of these two species and explore their molecular intraspecific diversity, we sequenced the genome of 12 M. graminicola isolates, representing populations of worldwide origins, and two South American isolates of M. oryzae. k-mer analysis of their nuclear genome and the detection of divergent homologous genomic sequences indicate that both species show a high proportion of heterozygous sites (ca. 1&ndash, 2%), which had never been previously reported in facultative meiotic parthenogenetic RKNs. These analyses also point to a distinct ploidy level in each species, compatible with a diploid M. graminicola and a triploid M. oryzae. Phylogenetic analyses of mitochondrial genomes and three nuclear genomic sequences confirm close relationships between these two species, with M. graminicola being a putative parent of M. oryzae. In addition, comparative mitogenomics of those 12 M. graminicola isolates with a Chinese published isolate reveal only 15 polymorphisms that are phylogenetically non-informative. Eight mitotypes are distinguished, the most common one being shared by distant populations from Asia and America. This low intraspecific diversity, coupled with a lack of phylogeographic signal, suggests a recent worldwide expansion of M. graminicola.

International audience; One hundred and forty six cuttings representing duplicates of 73 wild accessions from 16 coffee species were evaluated for resistance to Meloidogyne incognita race 1. Five species were subdivided on the asis of geographical origin because morphological differences were previously observed. Two wellcharacterized susceptible and resistant cultivars were used as comparative controls. The experiments were conducted in a greenhouse using a clonal population of M. incognita from Brazil. The reproduction factor (RF) was used to evaluate the resistance (RF1) to the nematode infection. Plants of both controls were discriminated on the basis of RF values. Both duplicate cuttings of the wild accessions were identically classified as resistant or susceptible. Eight species displayed a resistant reaction, onespecies was considered to be susceptible, and seven species presented both susceptible and resistant accessions. Resistance to M. incognita appeared to be a more frequent character than susceptibility within the gene pool of wild coffee. These results provide coffee breeders with material whose resistance can be transferred into commercial cultivars.; Ciento curaenta y seis estacas de 73 accesiones silvestres perteneciendo a 16 especies de café fueronevaluadas para su resistencia a Meloidogyne incognita raza 1. Se subdividió cinco especies según su origengeográfico en base a diferencias morfológicas previamente observadas. Los experimentos fueron realizadosen invernadero con una población clonal de M. incognita colectada en Brasil. Las resistencia ysusceptibilidad a este nematodo fueron evaluadas mediante el factor de reproducción (FR). Las plantas delos dos testigos fueron discriminadas en base a los valores del FR. Se observó siempre la mismaclasificación como resistente o susceptible de las dos estacas de cada una de las accesiones silvestresevaluadas. Ocho especies mostraron una respuesta de resistencia; una especie fue considerada comosusceptible y siete especies presentaron algunas accesiones susceptibles y otras resistentes. La resistencia aM. incognita parece ser más frecuente que el carácter de susceptibilidad dentro de la base genética de loscafetos silvestres. Los presentes resultados proveen a los fitomejoradores de café material vegetal cuyaresistencia puede ser transferida a cultivares comerciales

Studies have been conducted on rice yellow mottle virus (RYMV). RYMV diversity was investigated in Côte d'Ivoire and compared to other countries in Africa using immunological and molecular markers. Several strains of RYMV were identified. Two were found in Côte d'Ivoire (SI and S2), one numerically dominant in the south and the centre of the country (SI), the other in the north (S2). In mixed inoculation, there was a consistent dominance of S2 isolates over S1 isolates. Quantitative trait loci (QTL) of partial resistance in 0. sativa japonica were found on chromosome 12 with epistasic interaction with a QTL of chromosome 7 and involvement of QTLs linked to developmental genes such as the semi-dwarf gene. Partial resistance was expressed as a delay in virus accumulation, probably reflecting slower vascular and cell-to-cell virus movement in 0. japonica linked to the slower growth of that sub-species. The mestome peri-vascular cell layer may act as a further barrier to virus spread. Tolerance was also involved in the response of O. japonica to RYMV infection. Experiments in growth chambers indicated that there was no biological deterrent to abiotic transmission of the virus, but effective transmission through soil or water remains to be proved in the field. Studies have also been completed on other viruses such as African cassava mosaic virus, tomato yellow leaf curl and its transmission by thewhitefly Bemisia tabaci.