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International audience; A root-knot nematode parasitizing rice (Oryza sativa L.) in Santa Catarina state (Brazil) was identified as Meloidogyne oryzae Maas, Sanders and Dede, 1978 using different approaches. The specimens studied from this Brazilian population were compared with the type description of M. oryzae from Suriname, with additional morphological, biochemical and molecular characterization. The female has a longer stylet (15.0 μm) when compared with M. graminicola (11.2 μm) with irregularly shaped knobs, vulva offset and slightly protruding in posterior region. The lip region was distinct from first body annuli, and labial disc and the medial lips form an anchor-shaped structure. Perineal patterns were similar to M. graminicola. The male has a lip region offset and the presence of few short and irregular lines; medial lips divided, not fused with labial disc and stylet (18.2 μm) longer than in M. graminicola (16.8 μm). Second-stage juvenile (J2) tail (75.8 μm) was longer than in M. graminicola (70.9 μm) with a very long narrow hyaline portion (22 μm in M. oryzae and 17.9 μm in M. graminicola). Biochemically, it presented a distinct esterase profile (Est O1=R1), differentiating it from M. graminicola (Est VS1). The number of chromosomes was 3n = 50–56, and in DNA sequences of ITS1–5.8S–ITS2 rRNA the two populations of M. oryzae clustered together with other mitotic parthenogenetic species, differentiating them from M. graminicola with n = 18 chromosomes and clustered with meiotic species. Phylogenetic analysis using neutral markers (AFLP and RAPD) showed that both M. oryzae populations form a coherent, closely related cluster separately from M. graminicola isolates. This study represented the first detection of M. oryzae in Brazil and the second in the world after the species description in 1971.

International audience; Meloidogyne incognita is one of the most polyphagous species of root-knot nematodes occurring in Brazil and worldwide. Eight M. incognita isolates were studied, representing two enzymatic phenotypes (esterase and malate desydrogenase: I1/N1, I2/N1) and four cryptic Meloidogyne sp.1 (S2/N1) isolates, representing one cytological type (3n = 40-46). Three M. hispanica isolates (Hi3/N1, 2n = 32-36) and two of an atypical Meloidogyne sp.2 (S2a/N3, 3n = 40-44) were included in this study for comparison. All isolates were tested with three M. incognita-specific molecular markers. The primer pairs B06F/R, miF/R and incK14F/R amplified three species-specific fragments of 1,200 bp, 955 bp and 399 bp, respectively for M. incognita and Meloidogyne sp.1 isolates. No amplification occurred in the M. hispanica and Meloidogyne sp.2 isolates, except with primers miF/R (1,650 bp). The genetic variability of the Meloidogyne spp. isolates was evaluated, using RAPD and ISSR markers. The phylogenetic analyses revealed two strongly supported monophyletic clades: clade I, consisting of M. hispanica and the atypical Meloidogyne sp.2 isolates, and clade II, clustering together all M. incognita and the Meloidogyne sp.1 isolates. Considering the biometrical, cytological and molecular approaches, it was possible to conclude that the isolates with three enzymatic phenotypes (I1/N1, I2/N1 and S2/N1) presented the characteristics described for M. incognita. Some correlations were detected between the isozymatic phenotypes and the tree topology (S2a/N3, Hi3/N1, I1/N1, S2/N1), but no strict correlation could be observed for the phenotype I2/N1 and one isolate of S2/N1. Morphologically, the Msp.2 isolates differ from M. incognita and M. hispanica by the female stylet features presenting straight cone tip and round pear shaped knobs, posteriorly sloping. The results of this study suggested that the Msp.2 isolates with phenotypes S2aN3 belong to a new or an unidentified species closely related to M. hispanica.

International audience; The root-knot nematode (RKN) Meloidogyne mayaguensis is considered as one of the most damaging RKN species because of its extremely wide host range. Recent surveys have shown the rapid spread of this parasite in agro-ecosytems, often making crop cultivation not viable in the heavily infested areas. Here, we report the identification, molecular cloning, genomic organisation and sequence analysis of a new satellite DNA (satDNA) family from M. mayaguensis (named pMmPet). It is comprised of two groups of A+T rich, tandemly repeated units of 174 and 180 bp, respectively. Using these sequences as targets, hybridisation and PCR experiments performed on a wide collection of 44 populations belonging to 15 RKN species showed that the pMmPet family could only be detected in the 16 M. mayaguensis populations tested. In addition, because of their repetitive nature, positive detection of pMmPet sequences was achieved in single individual nematodes. Therefore, the repeated sequence described here possesses features that make it an excellent candidate for use as a specific and extremely sensitive tool for the accurate detection and identification of this invasive pest on a routine basis. Clearly, monitoring the occurrence and spread of M. mayaguensis at the domestic and international levels are needed to avoid wholesale loss of agricultural resources in the infested regions.