BackgroundPlant-parasitic nematodes developed strategies to invade and colonize their host plants, including expression of immune suppressors to overcome host defenses. Meloidogyne graminicola and M. incognita are root-knot nematode (RKN) species reported to damage rice (Oryza sativa L.) cultivated in upland and irrigated systems. Despite M. incognita wide host range, study of the molecular plant - RKN interaction has been so far limited to a few dicotyledonous model plants. The aim of this study was to investigate if the rice cv. Nipponbare widely used in rice genomic studies could be used as a suitable monocotyledon host plant for studying M. incognita pathogenicity mechanisms. Here we compared the ability of M. graminicola and M. incognita to develop and reproduce in Nipponbare roots. Next, we tested if RKNs modulates rice immunity-related genes expression in galls during infection and express the Mi-crt gene encoding an immune suppressor.ResultsRoot galling, mature females, eggs and newly formed J2s nematodes were obtained for both species in rice cultivated in hydroponic culture system after 4-5 weeks. Meloidogyne graminicola reproduced at higher rates than M. incognita on Nipponbare and the timing of infection was shorter. In contrast, the infection characteristics compared by histological analysis were similar for both nematode species. Giant cells formed from 2 days after infection (DAI) with M. graminicola and from 6 DAI with M. incognita. Real-time PCR (qRT-PCR) data indicated that RKNs are able to suppress transcription of immune regulators genes, such as OsEDS1, OsPAD4 and OsWRKY13 in young galls. Four M. incognita reference genes (Mi-eif-3, Mi-GDP-2, Mi-Y45F10D.4, and Mi-actin) were selected for normalizing nematode gene expression studies in planta and in pre-parasitic J2s. Meloidogyne incognita expressed the immune suppressor calreticulin gene (Mi-crt) in rice roots all along its infection cycle.ConclusionRKNs repress the transcription of key immune regulators in rice, likely in order to lower basal defence in newly-formed galls. The calreticulin Mi-CRT can be one of the immune-modulator effectors secreted by M. incognita in rice root tissues. Together, these data show that rice is a well suited model system to study host- M. incognita molecular interactions in monocotyledons.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-014-0023-4) contains supplementary material, which is available to authorized users.

There has been a strong demand for oat genotypes that contain caryopsis with high chemical quality which can suit the different market niches. Therefore, the objectives of this study were to assess the general (GCA) and specific combining ability (SCA) of white oat cultivars through diallelic crosses providing information about the genetic effects on expression of grain chemical quality components.

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Despite propagation of the cassava crop be done by cuttings for commercial purposes, the majority of accesses keeps active the sexual propagation system; what is essential to genetic breeding programs. Cassava seeds, however, have low and uneven germination rates. Considering such event, the objective of this study was to evaluate the efficiency of the storage, and different pre-germination treatments, on cassava seedling emergence. For this, an experiment was carried out with seeds obtained by open pollination between plants of four sweet cassava cultivars, with 10 pre-germination treatments; in addition to a control treatment. The viability of seeds subjected to different treatments was assessed by tetrazolium test; and the assessment of seedling emergence was performed by daily counts of the number of emerged seedlings. Data obtained were expressed in: emergence percentage; emergence speed index; and mean time of seedling emergence. It was concluded that storage, at 4 °C, during one year, increases seed emergence percentage and favors cassava seedling emergence speed; and that the dry heat (60 ºC), during seven and 14 days, also favors their emergence speed .

125Diallel analysis in white oat cultivars subjetecd to water stress

White oat genotypes were subjected to Al stress in hydroponic conditions in order to verify the viability of methods based on minimum nutrient solution (MNS) in comparison to complete nutrient solution (CNS), commonly used in the characterization and selection for Al tolerance in this species. The experimental design was completely randomized blocks with three replicates composed of 10 seedlings each. Six white oat genotypes subjected to different Al levels in minimum (0, 3, 6, and 9 mg L -1 ) and complete (0, 10, 20, and 30 mg L -1 ) solutions were evaluated. In this evaluation, the MNS was efficient in identifying aluminum-tolerant, white oat genotypes under hydroponics. The root growth resumption showed to be the most effective trait in the aluminum-tolerant plant selection. At concentrations equal to or higher than 3 mg Al L -1 in minimum and 10 mg Al L -1 in complete solution, severe damage caused by the toxic element on root development was verified. The white oat cultivars UFRGS 14, ALBASUL, and BARBARASUL showed aluminum tolerance in the tested conditions.

resumo A aveia preta no Brasil tem apresentado um forte incremento em área cultivada, principalmente com o advento da semeadura direta, rotação de culturas e adoção de sistemas agropecuários. Mesmo com estas características existem poucos trabalhos de pesquisa voltados para esta cultura, especialmente quanto a caracteres de importância agronômica e a identificação de genótipos adaptados às necessidades do produtor agrícola. Diante disto, o objetivo do trabalho foi avaliar caracteres relacionados à produção de forragem e dormência de sementes em populações de aveia preta originadas de cruzamentos artificiais realizados entre linhagens derivadas da cultivar "Preta Comum" e cultivares comerciais da espécie. Dois experimentos foram desenvolvidos no inverno de 2008, no município de Capão do Leão (RS), o primeiro com o objetivo de testar caracteres forrageiros e o segundo, para medir caracteres das sementes, como rendimento e nível de dormência. Os resultados indicaram que a hibridação artificial intensificou a variabilidade genética melhorando a expressão dos caracteres forrageiros, de rendimento de sementes e nível de dormência nas sementes. O caráter estande de plantas evidenciou elevada relação com a produtividade de matéria seca em estádios de desenvolvimento precoce das plantas; em fases mais adiantadas o número de afilhos teve maior contribuição na produção de biomassa. De modo geral, nas hibridações artificiais houve respostas diferenciadas para rendimento de sementes e nível de dormência, variando com os genitores utilizados na obtenção das populações. palavras-chave:Avena strigosa Schreb., populações híbridas, produção de forragem, dormência nas sementes. abstract GENETIC VARIABILITY FOR TOP AGRONOMIC CHARACTERISTICS IN BIPARENTAL CROSSES OF BLACK OATSThe area sown to black oat in Brazil has experienced a dramatic growth as a consequence of the expansion of minimum tillage, crop rotations and crop-livestock systems. This growth was not accompanied by research work providing data on the relevant agronomic traits from this forage grass, which would eventually lead to the creation of new varieties meeting the growers' demands. This work evaluated traits related to forage production and seed dormancy in black oat populations originating from artificial breeding between pure lines derived from the "Preta Comum" variety and commercial varieties from this species. Two experiments were carried out during the winter of 2008, at the Capão do Leão, Rio Grande do Sul State, one to assess forage production traits and the second to measure seed traits such as yield and dormancy levels. The results showed that artificial breeding enhanced genetic variability through improvement on the expression of forage traits, seed yield and dormancy levels. In relation to the former, plant stand was highly associated to dry matter production during the early stages of seedling development and establishment, while tiller production remained the major component explaining biomass production later stages of forage production. Artificial b...

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