Juvenil E. Cares

Protective effects of a cysteine proteinase propeptide expressed in transgenic soybean roots.

Sedentary endoparasitic nematodes cause extensive damage to a large number of ornamental plants and food crops, with estimated economical losses over 100 billion US

Detecção de Meloidogyne mayaguensis em goiabeira e mamoeiro no estado de Goiás, usando marcadores moleculares

worldwide. Various efforts have put forth in order to minimize nematode damage, which typically involve the use of nematicides that have high cost and enhanced toxicity to humans and the environment. Additionally, different strategies have been applied in order to develop genetically modified plants with improved nematode resistance. Among the strategies are anti-invasion and migration, feeding-cell attenuation, and anti-nematode feeding. In the present study, we focus on anti-nematode feeding, which involves the evaluation and potential use of the cysteine proteinase (CPs) propeptide as a control alternative. The cysteine proteinase prodomain, isolated from Heterodera glycines (HGCP prodomain), is a natural inhibitory peptide used to transform soybean cotyledons using Agrobacterium rhizogenes. Genetically modified soybean roots expressing the propeptide were detected by Western blot and expression levels were measured by ELISA (around 0.3%). The transgenic roots expressing the propeptide were inoculated with a thousand H. glycines at the second juvenile stage, and a remarkable reduction in the number of females and eggs was observed. A reduction of female length and diameter was also observed after 35 days post-inoculation. Furthermore, the H. glycines mature protein was detected in females fed on soybean transformed root expressing or not expressing the propeptide. The data presented here indicate that the HGCP propeptide can reduce soybean cyst nematode infection and this strategy could be applied in the near future to generate resistant crop cultivars.

Impact of nematode-induced galls on Miconia prasina (Sw.) DC (Melastomataceae) traits in the Atlantic forest of northeastern Brazil

Detection of Meloidogyne mayaguensis on guava and papaya in Goias State of Brazil using molecular markers Meloidogyne mayaguensis was reported for the first time in the State of Goias (Formosa and Luziânia), causing damage in oneyear old and 14 year-old commercial guava (Psidium guajava) cv. Paluma orchards. Plants infected by the nematode showed symptoms such as stunted growth, general chlorosis, nutrient deficiency and consequent decline in yield quality and quantity. Severely infested root systems were poorly developed, distorted by small and large multiple galls and devoid of fine roots. Plants of papaya cv. Formosa were cultivated in consortium with guava in the Formosa orchard and presented several galls in the root system, but no root-knot-nematode root-knot-nematode secondary symptoms were observed in the aerial part. The production of papaya fruits was high, evidencing tolerance of this cultivar to the symptoms were observed in the aerial part. The production of papaya fruits was high, evidencing tolerance of this cultivar to the were observed in the aerial part. The production of papaya fruits was high, evidencing tolerance of this cultivar to the nematode. The M2 phenotype (Rm: 0.7, 0.9) was detected for the isoenzyme esterase and M. mayaguensis was identified in both crops and orchards. The analyses with species-specific molecular markers using primers that amplify intergenic regions of the ribosomal DNA and the mitochondrial DNA confirmed the same diagnosis. Surveys carried out in other localities of the farm in Formosa detected the presence of Meloidogyne javanica javanica in low population, corroborating the idea that M. mayaguensis was introduced from the Petrolina nursery with the Petrolina nursery with

Nematode communities as indicators of the status of a soil ecosystem influenced by mining practices in Brazil

We tested the hypothesis that parasitic Ditylenchus sp., leaf gall inductor, decrease plant performance by reducing the number of leaves, shoots, and plant height, increasing herbivory damage and nematode colonization in aggregate plants. We compared the effects on 30 paired healthy and attacked individuals of Miconia prasina. Nematode infection did not affect the number of leaves and shoots and plant height. The damage by free-feeding herbivores was greater in healthy plants, while the number of insect galls was higher in attacked plants. The number of leaf miners did not vary. Healthy plants were more grouped than the attacked plants, and the mean plant distance and the index of nematode attack were positively related.

Contrastant banana accessions for resistance to the burrowing nematode, based on molecular markers RAPD

This study evaluated the effects of mining practices using soil nematodes as bioindicators. Soil samples represented four different subsystems found in the CeBio Research Center, including natural/undisturbed (rainforest (RF) and savannah (SA)) and disturbed ( Eucalyptus spp. (EU) and grassland (GR)) subsystems. Ecological descriptors S (3.5-9.5), d (1.22-4.23) and MI (1.9-3.23) significantly differentiated the subsystem GR (high impact) from the other subsystems. Additionally, poorly covered soil ( i.e. , subsystem GR) negatively influenced the composition of nematode assemblages, and primarily so for nematodes with high c-p values. Among soil variables, pH strongly influenced the distribution of soil nematodes, negatively affecting the abundance of all c-p groups and diversity of nematodes. On the other hand, pH also positively affected FF and PP trophic groups in the subsystem GR. The similarity of subsystem EU and natural subsystems (RF and SA) suggests that soil restoration with Eucalyptus spp. appears to be an adequate management practice to promote the recovery of areas subjected to mining practices.

Phylogeny and biogeography of the genus Cephalenchus (Tylenchomorpha, Nematoda)

This work aimed to proceed molecular characterization of seven banana accessions (Borneo, Grand Naine, 1304-06, 4249-05, 0337-02, 0323-03 and 4279-06) resistance to the nematode Radopholus similis. These accessions were selected taking in account the reproduction factor (RF) among 26 banana genotypes from a working collection belonging to Embrapa Mandioca e Fruticultura Tropical. The genomic DNA of the seven accessions was extracted, and 36 decamere primers had been used to obtain RAPD markers. The resulting markers were converted into a matrix of binary data. From that matrix the genetic distance between the accessions were estimated, for further clustering and graphic dispersion analyses. From a total of 521 RAPD markers generated, 420 (81%) were polymorphic, including 140 (27%) potentially promising for application on works related to genetic mapping of the resistance to R. similis. OPE-15, OPH-17, and OPG-09 were the primers that contributed to the highest number of bands promising for genetic mapping of resistance (12, 8, and 8, respectively). The genetic distances between accessions ranged from 0.106 to 0.455, with the longest one observed between cv. Borneo and the genotype 4279-06, considered as highly susceptible and resistant, respectively, to the nematode according to the RF. The graphic dispersion distinguished three groups of accessions, and most of resistant genotypes clustered together in the same group. The most contrastant genotypes for resistance (Borneo and 4249-05) were separated by a genetic distance of 0.374, and possessed a total of 114 polymorphic bands promising for genetic mapping of resistance. In addition, the results of pathogenicity tests were congruent with those obtained by RAPD analyses.

Plant-parasitic Nematodes Associated with Commercial Orchards of Passion Fruit and Adjacent Cerrado Vegetation in the Brazilian Federal District

The phylogenetic position of Cephalenchus is enigmatic with respect to other tylench nematodes. In this study, Cephalenchus populations representing 11 nominal species were sampled worldwide for molecular and morphological characterization. Species identification was based on light microscopy (LM) and scanning electron microscopy (SEM). Molecular analyses were based on the genes (i.e. 18S, 28S, 5.8S) and internal transcribed spacers (ITS‐1 and ITS‐2) of the ribosomal RNA (rRNA). Phylogenetic analyses (i.e. full and reduced alignments) of either concatenated or single genes always supported the monophyly of Cephalenchus. A sister relationship between Cephalenchus and Eutylenchus excretorius was recovered by most analyses, although branch support varies depending on the dataset used. The position of Cephalenchus + E. excretorius within Tylenchomorpha nevertheless remains ambiguous, thus highlighting the importance of sampling additional genes as well as taxa. Placement of Cephalenchus + E. excretorius as sister of Tylenchinae or Boleodorinae could not be rejected on the basis of 18S and 28S rRNA genes. Within Cephalenchus, amphidial opening morphology shows congruence with molecular‐based phylogenetic relationships, whereas the number of lines in the lateral field is likely to be a convergent trait. Morphometric analyses clearly distinguished short tail from medium–long tail species, and SEM observations seem to suggest a relation between tail length and amphidial opening. In addition, molecular phylogenies support the non‐monophyly of Cephalenchus cephalodiscus, Cephalenchus cylindricus, Cephalenchus daisuce and Cephalenchus leptus. The known extent of Cephalenchus diversity is increased with the inclusion of two new species, and the biogeography of the genus is discussed.

Detection of Meloidogyne arenaria in cucumber in Rio Grande do Sul state, Brazil

Empresa Brasileira de Pesquisa Agropecuaria, Embrapa Cerrados, BR 020, Km 18, 73310-970, Planaltina, DF, Brazil(Received on January 18, 2012; Revised on July 6, 2012; Accepted on July 7, 2012)Populations of plant-parasitic nematodes were evaluat-ed in soil and root samples from areas planted withpassion fruit, or covered with adjacent native cerradovegetation, in five different cropping regions of theBrazilian Federal District. From July 2007 to January2008, twenty samples had been collected in five RuralCenters (Nucleo Rural–NR) planted with passion fruit.In five sites, samples were also collected in native cerradovegetation. Specimens of nine genera of plant-parasiticnematodes ( Meloidogyne , Helicotylenchus , Rotylenchulus ,Scutellonema, Pratylenchus, Paratylenchus, Hemicyclio-phora, Xiphinema and Criconemoides ) were found in thepresent survey. Important nematode pathogens, such asRotylenchulus reniformis and Meloidogyne spp. wereobserved in the passion fruit plantations throughoutfive major producing regions of the Brazilian FederalDistrict. Keywords : field survey, Meloyogyne, Passiflora spp, root-knot nematodes, Rotylenchulus reniformisPassiflora edulis Simmonds f. flavicarpa Degener is aplant species of a high economic importance in America,whereas Brazil and Ecuador are important world producersand consumers of passion fruit (Souza et al., 2008). Theeconomic importance of P. edulis and other Passifloraspecies relies on the quality of the fruits for consumptionand on its medicinal properties (Crochemore et al., 2003).Due to favorable climatic and soil conditions, extensiveproduction of sour passion fruit occurs in commercialorchards in the Brazilian Cerrado. Despite the advantages mentioned above, sour passionfruit is susceptible to pests and diseases. Soil pathogens areof main concern among passion fruit growers, especiallyplant-parasitic nematodes. Nematodes belonging to severalgenera have been reported in association with Passifloraroot systems in Brazil (Sharma et al., 1999; Soares et al.,2003; Dias-Arieira et al., 2008), however, for the majorityof them their role as pathogens remains unknown forthis crop. On the other side, the root-knot nematodes(Meloidogyne javanica, M. incognita, and M. arenaria),and the reniform nematode (Rotylenchulus reniformis) areamong the most destructive soil pathogens for passion fruit.These sedentary nematodes lead to root damage, poor plantdevelopment, and consequently to decreased yield andplant longevity.In addition to preventive measures, such as planting insoil free of harmful nematodes, crop rotation is the mostappropriate control measure available to lower populationlevels of nematodes in passion fruit plantations underBrazilian conditions. At the present time there is no nemati-cide registered for this crop. Despite richness of geneticvariability among Passiflora germplasm, and efforts tobreed nematode resistant varieties (Castro et al., 2011; El-Moor et al., 2009; Sharma et al., 2002), commercial vari-eties are not yet available to growers. Thus, knowledge ofthe distribution and population levels of nematodes isrequired for implementation of management practices.Direct field seeding, instead of planting seedlings fromnurseries is a common practice among passion fruit growersin the Brazilian Federal District (DF). This practice contri-butes to avoid dissemination of nematodes and otherpathogens from the nurseries through planting materials.Under these conditions, the sources of soil contamination ofplant-parasitic nematodes in the commercial orchards arepossibly from previous crops, weeds, or accidental intro-duction of infested soil from other locations. Susceptibleplants from the native vegetation may also be the source ofplant-parasitic nematodes when the area is claimed foragricultural purposes. For instance, Souza et al. (1994)reported the association of Meloidogyne spp. with severalnative plants of cerrado vegetation in Brazilian FederalDistrict (DF). The fact that the same plant-parasitic nema-todes appear associated with crops and plants in theassociated native vegetation is an indication that these

Comparison of two methods for in vitro multiplication of Radopholus similis and Pratylenchus brachyurus in carrot cylinders

Diseased cucumber plants with symptoms of decline and root knots were collected from a crop in the municipality of Faxinal do Soturno, Rio Grande do Sul state, Brazil. Morphological (perineal patterns), biochemical (esterase phenotypes) and molecular (D2–D3 region) studies allowed to identify parasitizing nematodes, such as Meloidogyne arenaria. To our knowledge, this is the first report of Meloidogyne arenaria on Cucumber in Rio Grande do Sul State, Brazil.

Nematode community, trophic structure and population fluctuation in soybean fields

The use of in vitro mass multiplication of nematodes under axenic conditions allows intensification of studies on taxonomy, biology, epidemiology and control of these pathogens. In the present study, two methods were compared for in vitro multiplication of two species of plant-parasitic nematodes, Radopholus similis and Pratylenchus brachyurus in 20, 40 and 60 day-periods. Both techniques involved the use of carrot cylinders placed in jars with lids, with water-agar in the bottom of the flasks (WA+) or without (WA-). In WA- the nematodes were treated with a 1% solution of ampicillin whilst for WA+ the axenization was carried out with a solution of mercuric chloride (0.01%), and streptomycin sulfate 0.02%. The WA+ condition was the most favorable for multiplication of both species of nematodes, resulting in a population increase of about 280 times for R. similis and 226 times for P. brachyurus in relation to the founding population of 25 individuals. For WA- a population increase of only five times after 60 days for R. similis and a duplication of the population after 60 days for P. brachyurus was obtained. Overall, the largest amount of nematodes occurred at 60 days after inoculation.