Caracterização de novas espécies virais infectando plantas forrageiras no Brasil e reação de genótipos de Panicum maximum à virose.

Em área experimental da Embrapa Gado de Corte, Campo Grande-MS, genótipos de espécies de Panicum, Brachiaria e Stylosanthes têm exibido sintomas típicos de infecção viral, como mosaico nas folhas e redução do crescimento da parte aérea, cuja etiologia ainda não estava esclarecida. Fontes de resistência são as principais formas de controle da doença. Objetivou-se, neste trabalho, identificar o(s) vírus agente(s) da doença, bem como fontes de resistência de P. maximum à mesma. Folhas sintomáticas foram maceradas em tampão PBS e o extrato foliar foi centrifugado e filtrado. O RNA viral foi extraído utilizando-se RNeasy Mini Kit, de acordo com as instruções do fabricante. As amostras de RNA foram concentradas e sequenciadas na Macrogen inc. (Korea) usando-se a tecnologia Illumina HiSeq de 2000. Obtiveram-se cerca de 48 milhões de sequências, que foram processadas e montadas?de novo? usando-se CLC Genomics Workbench 7.0

Near-infrared reflectance spectroscopy as a tool for breeding Andropogon gayanusKunth for forage quality.

Abstract: The objective was to investigate the usefulness of Near Infrared Spectroscopy (NIRS) to predict bromatological traits concentrations of gamba grass (Andropogon gayanus Kunth). Random samples from different plant genetic backgrounds, climatic conditions over years, experimental sites, and harvests were used for spectral reading and reference analysis. Partial Least Square (PLS) regressions were used for developing the models with 239 samples for calibration and 119 for external validation. Crude Protein, Ash, and Dry Matter models had R2= 0.91, 0.91, and 0.90 and low standard errors of calibration (SEC) of 8.7, 3.8, and 5.5 g.kg-1 , respectively. Neutral and Acid Detergent Fibers, and Organic Matter had R2 = 0.85, 0.88, and 0.89 and SEC valuesof10.2, 9.4, and 7.9 g.kg-1 , respectively. In vitro digestibility of dry matter had R2= 0.79 and SEC 28.0 g.kg-1 . Acid Detergent Lignin had a poor fit with R2= 0.36.A high correlation between NIRS predictions and wet lab data was observed. Models were adequate and accurate for predicting all bromatological traits but ADL. Significative differences among 51 half-sib families were detected for quality traits predicted throughPLS models. NIRS can be effectively used in gamba grass breeding programs for selecting superior forage quality genotypes. -------------------------------------------------------------------------------------------------------------------------

Soybean rust resistance sources and inheritance in the common bean (Phaseolus vulgaris L.).

Soybean rust (SBR), caused by the fungus Phakopsora pachyrhizi, has been reported in common bean (Phaseolus vulgaris L.) cultivars and elite lines that were infected under controlled and natural field conditions in South Africa, the United States, Argentina, and Brazil. Although SBR is currently not a top priority problem for the common bean crop, many bean breeders are concerned about this disease because of the high severity and virulence diversity of P. pachyrhizi and its broad host range. In this study, a set of 44 P. vulgaris genotypes were tested for resistance to P. pachyrhizi; these genotypes included resistance sources to several fungal common bean diseases, carioca-, black- and red-seeded Brazilian cultivars, and elite lines that were developed by the main common bean breeding programs in Brazil. Twenty-four SBR resistance sources were identified. They presented the reddish-brown (RB) lesion type, characterizing resistance reactions. In addition to the RB lesion type, the PI181996 line presented the lowest disease severity mean score, considering its associated standard error value. For this reason, it was crossed with susceptible lines to study the inheritance of resistance. The results support the hypothesis that resistance to SBR in PI181996 is monogenic and dominant. We propose that this SBR resistance gene, the first to be identified and characterized in common bean, might be designated as Pkp-1.201

Biological and molecular characterization of a highly divergent johnsongrass mosaic virus isolate from Pennisetum purpureum.

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DNA marker-assisted selection to pyramid rust resistance genes in “carioca” seeded common bean lines

This work reports a gene pyramiding approach assisted by DNA markers used to develop “carioca” seeded common bean (Phaseolus vulgaris L.) elite lines harboring three different rust resistance genes. Rust is among the most destructive diseases that attack P. vulgaris and cause serious damage worldwide. The rust resistance genes Ur-5 (from ‘Mexico 309’), Ur-11 (from ‘BelMiDak RR-3’), and Ur-14 (from ‘BRS Pioneiro’, a “carioca” seeded cultivar derived from the resistance source ‘Ouro Negro’) were combined in the “carioca” seeded bean cultivar ‘Rudá’. Firstly, two different backcross programs were conducted separately to produce progenies harboring individually the Ur-5 and Ur-11 genes. Molecular fingerprinting analysis was used to select plants genetically similar to ‘Rudá’ in the backcross cycles to accelerate the recurrent-background recovery. The obtained progenies were initially intercrossed and then crossed with ‘BRSMG Pioneiro’ (Ur-14). The final F1 plants derived from these crosses were screened with DNA markers linked to the three rust resistance genes: SI19 (Ur-5), SAE19 (Ur-11) and OPX11 (Ur-14). The plants selected as harboring all the alleles of interest were used to obtain the next generations. The selection based on DNA markers was conducted up to the F4:5 generation. We were able to select F4:7 progenies showing all the DNA markers associated to the genes of interest and resistant to all specific races of U. appendiculatus used for phenotypically detecting each one of the rust resistance genes. Yield evaluations show that these selected lines are as productive as the recurrent parent ‘Rudá’ and high-performing control cultivars grown in Brazil

Breeding for common bean (Phaseolus vulgaris L.) rust resistance in Brazil.

Common bean is an economically, nutritionally, and socially important crop. It is grown in distinct regions and different seasons around the world by subsistence level farmers with low-technology input as well as by farmers that use high input technologies. One important factor that can limit the bean growing and drastically affect grain yields is the high number of destructive pathogens that attack and cause serious damage to the crop. Among them is bean rust, incited by the fungus Uromyces appendiculatus. This disease is distributed throughout the world, but it effectively causes major production problems in humid tropical and subtropical regions. In Brazil, rust causes major losses in south, southeast, and central regions of the country. Bean rust control by resistant cultivars is an easy and economical strategy to be used in association to other rust management practices. Pyramiding of different race-specific resistance genes in association with other genes conferring adult plant resistance, slow rusting, and reduced pustule size can prolong the lifespan of a common bean cultivar by creating a more durable resistance complex against the rust pathogen. This review manuscript presents an overview on bean rust and reports some breeding efforts aiming to develop rust resistant cultivars in Brazil.201