The root-knot nematode (Meloidogyne incognita) is one of most devastating pathogens that attack the common bean crop. Although there is evidence that some cultivars have race-specific resistance against M. incognita, these resistance sources have not proved effective, and nematodes are able to circumvent the host's defense system. We constructed RNA-seq based libraries and used a high-throughput sequencing platform to analyze the plant responses to M. incognita. Assessments were performed at 4 and 10 days after inoculation corresponding to the stages of nematode penetration and giant cell development, respectively. Large-scale transcript mapping to the common bean reference genome (G19833) resulted in the identification of 27,195 unigenes. Of these, 797 host genes were found to be differentially expressed. The functional annotation results confirm the complex interplay between abiotic and biotic stress signaling pathways. High expression levels of the wounding-responsive genes were observed over the interaction. At early response, an overexpression of the N gene, a TIR-NBS-LRR resistance gene, was understood as a host attempt to overcome the pathogen attack. However, the repression of heat shock proteins resulted in a lack of reactive oxygen species accumulation and absence of a hypersensitive response. Furthermore, the host basal response was broken by the repression of the ethylene/jasmonate pathway later in the response, resulting in a continuous compatible process with consequent plant susceptibility.

Nematodes are devastating pests that infect most cultivated plant species and cause considerable agricultural losses worldwide. The understanding of metabolic adjustments induced during plant-nematode interaction is crucial to generate resistant plants or to select more efficient molecules to fight against this pest. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) has been used herein for in situ detection and mapping endogenous polypeptides and secondary metabolites from nematode-induced gall tissue. One of the major critical features of this technique is sample preparation; mainly, the generation of intact sections of plant cells with their rigid cell walls and vacuolated cytoplasm. Our experimental settings allowed us to obtain sections without contamination of exogenous ions or diffusion of molecules and to map the differential presence of low and high molecular weight ions in uninfected roots compared with nematode-induced galls. We predict the presence of lipids in both uninfected roots and galls, which was validated by MALDI time-of-flight tandem mass spectrometry and high-resolution mass spectrometry analysis of lipid extracts. Based on the isotopic ion distribution profile, both esters and glycerophospholipids were predicted compounds and may be playing an important role in gall development. Our results indicate that the MALDI-MSI technology is a promising tool to identify secondary metabolites as well as peptides and proteins in complex plant tissues like galls to decipher molecular processes responsible for infection and maintenance of these feeding sites during nematode parasitism.

352 SummaryRoots of Syagrus oleracea were collected in two growing areas in the municipality of Rio Verde, state of Goiás (Brazil). Morphological, morphometric and molecular (ITS1 sequences) approaches allowed us to identify the infecting nematode as Pratylenchus brachyurus. To our knowledge, this is the first record of P. brachyurus parasitizing guariroba elsewhere (new host).

This paper evaluates the transmission of S. sclerotium from infected soybean seeds to seedlings. Results showed that a lower emergence percentage and speed was obtained after 24h inoculation without asepsis; the transmission of S. sclerotiorum therefore occurred from soybean seeds to symptomatic seedlings. Asymptomatic seedlings do not present the fungus, indicating no transmission.

No abstract

Phytonematodes are among the main pathogens of the common bean. In general, control practices that aim to control these pathogens have not been regularly adopted in Brazil. The objectives of the present study were to evaluate the occurrence of phytonematodes in dry bean fields in Paraná and São Paulo states and estimate the pathogenicity of Pratylenchus brachyurus to dry bean in glasshouse experiments. Root and soil were sampled for nematode extraction, identification and estimation of population density. Four glasshouse experiments with different initial population densities were carried out to evaluate the effect of P. brachyurus on the growth of dry bean plants. Six species of phytonematodes were detected, namely Helicotylenchus dihystera, P. brachyurus, Pratylenchus crenatus, Meloidogyne javanica, Meloidogyne incognita and Rotylenchulus sp. The spiral nematode H. dihystera was found in all samples and was the most abundant species in both states. The lesion nematode P. brachyurus was also frequent, reaching 94% in Paraná and 100% in São Paulo. The root-knot nematodes and Rotylenchulus sp. were reported only in São Paulo fields (45% and 18% frequency, respectively), and P. crenatus only in Paraná (12%). The most abundant nematode in the soil was H. dihystera, and in roots was P. crenatus. It was demonstrated that densities of 6.66 specimens of P. brachyurus per cm 3 of soil provoke visible and measurable root decay. In conclusion, survey data showed low phytonematode densities and pathogenicity tests demonstrated that densities above 6.67 specimens of P. brachyurus per cm 3 of soil cause damage to the dry bean roots.

O cultivo da mandioca é realizado na maioria dos municípios e estados brasileiros, sendo uma pequena parte destinada ao consumo in natura e a maior parte para a produção de farinha e extração de amido. Embora seja uma planta rústica, diversos fatores bióticos e abióticos podem reduzir a produtividade da cultura. As doenças viróticas causam impacto na cultura, principalmente devido a eficiente disseminação do patógeno por meio da propagação vegetativa das manivas infectadas e degenerescência das raízes. No Brasil já foram relatados o Cassava common mosaic virus (CsCMV), Cassava vein mosaic virus (CsVMV), e Cassava frogskin disease, destacando-se os dois primeiros como os mais disseminados no país.

RESUMO - A podridão seca das raízes é uma das doenças mais destrutivas da mandioca (Manihot esculenta Crantz) podendo ocasionar perdas de produção de 30% à 100%. Este trabalho teve por objetivo avaliar cultivares e clones avançados provenientes do programa de melhoramento genético de mandioca da EPAGRI, quanto à resistência à podridão seca causada por Fusarium solani. Uma suspensão de esporos de isolados de F. solani foi inoculada sobre discos de raízes de 21 genótipos de mandioca na concentração de 1,5 x 107 conídios.mL-1 em quatro experimentos. A severidade da doença foi avaliada por meio da porcentagem da área afetada pelo fungo. As manivas dos genótipos mais promissores nos testes de resistência foram selecionadas para testes com F. solani em casa de vegetação. O genótipo Luna foi o mais resistente dentre os avaliados e apresentou elevados valores de massa fresca de parte aérea e de raízes, tendo potencial para ser utilizado em áreas infestadas por F. solani e/ou como progenitor no melhoramento da cultura. Também os genótipos SC12-5035 e SC 12-5029 apresentaram potencial para uso em programas de manejo integrado da doença.