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The Cerrado biome represents a hotspot of biodiversity. Despite this, the nematofauna in this biome has not been well characterized, especially that related to root-knot nematodes. This work aimed to identify Meloidogyne species present in different cerrado vegetations and to investigate potential hosts of Meloidogyne javanica in this biome. Soil samples (250) were collected in native areas of cerrado vegetation located at the National Park of Brasilia (PNB) (125 samples) and Agua Limpa Farm (FAL) (125 samples), and transferred to sterile pots. Single tomato plants cv. Santa Clara (susceptible) were transplanted into individual pots and maintained for 90 days under glasshouse. Females of Meloidogyne spp. were extracted from tomato roots and identified based upon esterase phenotypes and confirmed with PCR using specific sequence characterized amplified regions (SCAR) primers. Native plants were inoculated with 10 000 individuals (eggs + J2) of a pure culture of M. javanica and maintained under glasshouse for 6 months. From the 250 samples collected, 57 (22.8%) presented Meloidogyne spp. A total of 66 Meloidogyne populations were identified as follows: M. javanica (75.76%), M. incognita (10.60%), M. hapla (9.1%), M. morocciensis (3.03%) and M. arenaria (1.51%). The following esterase phenotypes were detected: M. javanica (J3 and J2), M. incognita (I1 and I2), M. hapla (H1), M. morocciensis (A3) and M. arenaria (A2). The SCAR primers incK14F/incK14R, Fjav/Rjav and Fh/Rh amplified specific fragments in M. incognita (399 bp), M. javanica (670 bp) and M. hapla (610 bp) and can be used for identification of indigenous Meloidogyne spp. from cerrado. The primer set Far/Rar is not specific for M. arenaria due to the amplification of DNA in M. morocciensis. Mimosa caesalpiniifolia was the only native plant in which M. javanica developed a high reproductive rate, and it is probably a host for this nematode in cerrado.

Meloidogyne enterolobii has been reported in some states of Brazil and other countries causing severe damage on commercial guava (Psidium guajava). The use of resistant varieties is the most effective way to manage nematode parasitism. This study screened 51 accessions of Psidium spp. selected from the Psidium Germplasm Collection (Embrapa) to look for resistance against M. enterolobii. Six months after inoculation, nematode reproduction factor (RF) was used to assess resistance. The following species were resistant to M. enterolobii: P. cattleianum (yellow guava), P. friedrichsthalianum (Costa Rican guava), Acca sellowiana (feijoa) and P. rufum (purple guava). All 43 wild accessions of P. guajava were susceptible, as well as three accessions of P. guineense (Brazilian guava), one of P. acutangulum (pear guava) and the susceptible control P. guajava cv. Paluma. When used as rootstocks under greenhouse conditions, P. cattleianum and P. friedrichsthalianum were compatible with cv. Paluma; however, in greenhouse and field conditions only 50% of both scions survived. No apparent hypersensitive response (HR) was seen in the resistant guava P. cattleianum and P. friedrichsthalianum. Juveniles were able to develop normal feeding sites similar to those in susceptible roots 6–13 days after inoculation (dai). From 27 to 32 dai, giant cell deterioration was observed and nematodes showed arrested development. The majority of nematodes failed to reach maturity and did not begin laying eggs in resistant roots. These results suggested that the induction of resistance is relatively late in this pathosystem.

International audience; Meloidogyne ethiopica is an important nematode pathogen causing serious economic damage to grapevine in Chile. In Brazil, M.ethiopica has been detected with low frequency in kiwifruit and other crops. The objectives of this study were to evaluate the intraspecific genetic variability of M.ethiopica isolates from Brazil and Chile using AFLP and RAPD markers and to develop a species-specific SCAR-PCR assay for its diagnosis. Fourteen isolates were obtained from different geographic regions or host plants. Three isolates of an undescribed Meloidogyne species and one isolate of M.ethiopica from Kenya were included in the analysis. The results showed a low level of diversity among the M.ethiopica isolates, regardless of their geographical distribution or host plant origin. The three isolates of Meloidogyne sp. showed a high homogeneity and clustered separately from M.ethiopica (100% bootstrap). RAPD screenings of M.ethiopica allowed the identification of a differential DNA fragment that was converted into a SCAR marker. Using genomic DNA from pooled nematodes as a template, PCR amplification with primers designed from this species-specific SCAR produced a fragment of 350bp in all 14 isolates of M.ethiopica tested, in contrast with other species tested. This primer pair also allowed successful amplification of DNA from single nematodes, either juveniles or females and when used in multiplex PCR reactions containing mixtures of other root-knot nematode species, thus showing the sensitivity of the assay. Therefore, the method developed here has potential for application in routine diagnostic procedures.