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.

Root-knot nematodes (RKN) are important plant pathogens affecting rice in South-East Asia and southern Brazil in irrigated rice fields. In order to investigate the specific diversity of RKN associated with irrigated rice in southern Brazil, Meloidogyne spp. from Rio Grande do Sul (RS) and Santa Catarina (SC) States were characterised biochemically by esterase (Est) and malate dehydrogenase (Mdh) phenotypes. Fifty-six Meloidogyne spp. populations were detected in 48% of rice samples, and a total of fiveesterase phenotypes were identified, four of which presented as drawn-out bands in different positions. In RS State, M. graminicola (Est VS1), Meloidogyne sp. 2 (Est R2) and Meloidogyne sp. 3 (Est R3) were identified, which corresponded to ca 80, 40 and 10% of samples, respectively. In SC State, M. graminicola, M. javanica (Est J3), Meloidogyne sp. 1 (Est R1), Meloidogyne sp. 2 and Meloidogyne sp.3 accounted for ca 93.75, 12.50, 62.50, 12.25 and 6.25% of samples, respectively. The esterase phenotypes R1, R2 and R3 are new, never having been detected on rice before. Meloidogyne javanica showed a N1 Mdh phenotype (Rm: 1.0), while four other populations exhibited a N1a (Rm: 1.4) phenotype. All populations were tested with two SCAR markers specific to M. graminicola, which confirmed that, but no specificity was obtained with both markers in relation to the atypical populations analysed. Sequencing and phylogenetic analyses of internal transcribed spacer-rRNA (ITS) were performed to infer the phylogenetic relationship of these atypical Meloidogyne spp. populations. Meloidogyne sp. 1 grouped with the mitotic parthenogenetic species, while the two others (Meloidogyne sp. 2 and sp. 3) clustered with M. graminicola and other meiotic parthenogenetic species. Taken together, these data highlight the unprecedented specific diversity of RKN associated with irrigated rice in southern Brazil. Further morphological and phylogenetic studies involvingthese atypical isolates will be carried out to identify this complex of species

This study aimed to evaluate the biocontrol potential of bacteria isolated from different plant species and soils. The production of compounds related to phytopathogen biocontrol and/or promotion of plant growth in bacterial isolates was evaluated by measuring the production of antimicrobial compounds (ammonia and antibiosis) and hydrolytic enzymes (amylases, lipases, proteases, and chitinases) and phosphate solubilization. Of the 1219 bacterial isolates, 92% produced one or more of the eight compounds evaluated, but only 1% of the isolates produced all the compounds. Proteolytic activity was most frequently observed among the bacterial isolates. Among the compounds which often determine the success of biocontrol, 43% produced compounds which inhibit mycelial growth of Monilinia fructicola, but only 11% hydrolyzed chitin. Bacteria from different plant species (rhizosphere or phylloplane) exhibited differences in the ability to produce the compounds evaluated. Most bacterial isolates with biocontrol potential were isolated from rhizospheric soil. The most efficient bacteria (producing at least five compounds related to phytopathogen biocontrol and/or plant growth), 86 in total, were evaluated for their biocontrol potential by observing their ability to kill juvenile Mesocriconema xenoplax. Thus, we clearly observed that bacteria that produced more compounds related to phytopathogen biocontrol and/or plant growth had a higher efficacy for nematode biocontrol, which validated the selection strategy used.

Root-knot nematodes (Meloidogyne spp.) significantly impact potato production worldwide and in Brazil they are considered one of the most important group of nematodes affecting potatoes. The objectives of this study were to survey Meloidogyne spp. associated with potatoes in Brazil, determine their genetic diversity and assess the aggressiveness of M. javanica on two susceptible potato cultivars. Fifty-seven root-knot nematode populations were identified using esterase phenotyping, including Meloidogyne javanica, M. incognita, M. arenaria and M. ethiopica. Overall, root-knot nematodes were present in ca 43% of sampled sites, in which M. javanica was the most prevalent species, and the phenotypes Est J3, J2a and J2 occurred in 91.2, 6.7 and 2.1% of the positive samples, respectively. Other species, such as M. incognita, M. arenaria and M. ethiopica, were found less frequently and occurred at rates of 6.4, 4.3 and 2.1% of the samples, respectively. Sometimes, M. javanica was found in mixtures with other root-knot nematodes in ca 10.6% of sites containing Meloidogyne. After confirming the identification of 17 isolates of M. javanica and one isolate each of M. incognita, M. arenaria and M. ethiopica by SCAR markers, the populations were used to infer their genetic diversity using RAPD markers. Results revealed low intraspecifc genetic diversity among isolates (13.9%) for M. javanica. Similarly, M. javanica sub-populations (J2a) clustered together (81% of bootstrap), indicating subtle variation from typical J3 populations. The aggressiveness of four populations of M. javanica from different Brazilian states on two susceptible potato cultivars was tested under glasshouse conditions. Results indicated differences in aggressiveness among these populations and showed that potato disease was proportional to nematode reproduction factor.

The worst nematode problem affecting guava is that created by root-knot nematode, which is a recognized limiting factor in commercial guava production in Central and South America. Considering the difficulty of identifying Meloidogyne enterolobii (=M. mayaguensis) only by the perineal pattern, this species has been misidentified in different regions around the world and identified frequently as M. incognita or Meloidogyne spp. The species' identification is possible using esterase phenotype and molecular markers. Using these techniques, only M. enterolobii was detected on guava in Brazil, confirming the incorrect identification. The intraspecific genetic variability of 16 M. enterolobii isolates from different geographical regions and hosts were analysed with different neutral molecular markers (RAPD, ISSR and AFLP) and showed a high level of homogeneity among the populations. Considering the low variability among M. enterolobii isolates, genetic resistance could be considered the most effective method of control, but only one accession of P. friedrichstalianium (Costa Rican wild guava) was resistant and compatible as rootstock with P. guajava 'Paluma', in field conditions. Although this root-knot nematode displays a very wide host range, studies showed that crop rotation is possible for cleaning areas infested with the nematode, using 35 antagonistic plants. Some cultivars of corn are also very promising for use in reducing populations of M. enterolobii in infested fields. Fourteen fruit trees are nonhost to M. enterolobii and only four fruit trees are good hosts. Considering the impossibility of cultivating guava in fields infested by M. enterolobii, crops presented as non-hosts or poor hosts could be used by the growers, but more studies should be done in the field, in infested areas, to support the results obtained in greenhouse conditions.

Potential of microbiolization of rice seeds with rhizobacteria for root-knot nematode biocontrolThe potential of eight rhizobacteria that effectively control fungal diseases in rice [DFs185 (Pseudomonas synxantha), DFs223 (P. fluorescens), DFs306 (not identified), DFs416, DFs418 e DFs419 (Bacillus sp.), DFs422 (Bacillus subtilis), DFs471 (Stenotrophomonas malthophilia)] was evaluated for the control of Meloidogyne graminicola in vitro and in irrigated rice in the greenhouse. The rhizobacteria DFs185, DFs223, DFs306, DFs416 and DFs419 exceeded in reducing hatching and in increasing the mortality of M. graminicola J2. All rhizobacteria were able to produce at least one compound associated with the biocontrol of nematodes (chitinasis, phosphatases, lipases, proteinasis and siderophores). The number of eggs and galls of M. graminicola in rice plants was reduced compared to plants from seeds not microbiolized. The nematode reproduction factor was reduced on average by 29%, highlighting rhizobacteria DFs185 and DFs223 that reduced 35%. This result is significant because the rhizobacteria also control fungal diseases.

Summary The rice root-knot nematode, Meloidogyne graminicola, has been reported in Southeast Asia, China, India, South Africa, USA, Brazil, and other countries. Recent surveys in Southern Brazil showed that M. graminicola was widespread in irrigated rice in Rio Grande do Sul, Santa Catarina and Paraná states, and the presence of a species complex with a predominance of M. graminicola (Est VS1 = G1) and other variants showing similar esterase phenotypes (Est G2 = R2, G3 = R3). Meloidogyne oryzae (Est O1) and M. ottersoni (Est Ot0) were also part of this complex and were recently re-described and detected on rice. The present study provides an integrative taxonomy approach of the typical and atypical populations of M. graminicola on the basis of morphological, morphometric and molecular data. Considering morphological and morphometric features, the two atypical populations (Est G2 and G3) are in close agreement with the description of M. graminicola. Based on the molecular characterisation, populations G1, G2 and G3 were successfully amplified by M. graminicola SCAR markers, although the specificity of these markers was questioned. Phylogenetic relationships complemented and confirmed the other studies. In maximum likelihood analysis of ITS, D2-D3 rRNA and COXII-16S rRNA sequences, all populations of M. graminicola from different esterase phenotypes clustered together with other M. graminicola populations, thus confirming that these enzyme phenotypes (G1, G2 and G3) are related to the same species. A high level of intraspecific variability was detected among all populations, but no correlation between genetic variability and geographic origins occurred.

Meloidogyne enterolobii (syn. M. mayaguensis) has been reported to cause severe damage in commercial guava orchards and other plants in Central and South American countries. Considering the risk of introduction and dissemination of this pest in the European region, M. enterolobii was placed on the EPPO A2 list in 2010. The use of non-host fruit species is a recommended strategy to manage rootknot nematodes in infested guava orchards. This study screened 89 plant genotypes from 25 fruit plants of economic importance, plus two susceptible controls (guava and tomato) for its host status to M. enterolobii. Three to eight months after inoculation, nematode reproduction factor (RF) was used to characterize host suitability of fruit crops to this nematode. Ten banana genotypes, six Barbados cherries, one fig, two grape rootstocks and six melons were rated as good hosts for this nematode. Sixteen fruit plants behaved either as non-hosts or poor hosts to M. enterolobii, including assaí, atemoya, avocado, cashew nut, citrus, coconut, grape, jabuticaba, mango, mulberry, papaya, passion fruit, sapodilla, soursop, starfruit and strawberry. For the future, field experiments in areas infested by this nematode are essential to confirm the greenhouse results. These non-host fruit species can replace in the future eradicated guava trees in fields severely infested by this nematode and become an economic option for growers where M. enterolobii is considered a serious problem.