Resumen Se planteó la hipótesis de que es posible que el inóculo de diferentes especies de rumiantes con capacidades digestivas diferentes que se alimentan de un determinado forraje puede mostrar diferentes utilizaciones de alimento en comparación con otras especies de rumiantes. Se evaluaron cinco gramíneas Brachiaria: B. decumbens cv. Basilisk, B. decumbens acceso D70, B. humidicola cv. Tupi, B. humidicola cv. Común, y B. ruziziensis acceso R124, en dos edades de rebrote (21 y 42 d). Se analizó la producción, el contenido bromatológico, la digestibilidad de materia seca in vitro (DMSiv) y la digestibilidad de la fibra detergente neutro in vitro (DFDNiv) utilizando inóculos bovinos u ovinos. El experimento utilizó un diseño factorial de 5 × 2 × 2 y encontró efectos significativos para la variedad de gramínea y la edad de rebrote. Además, se encontraron interacciones significativas de gramínea × edad en la materia seca, la proteína cruda, la fibra detergente neutro y la fibra detergente ácido de la muestra total y lamina de la hoja. Hubo un efecto significativo de la variedad de gramínea y la edad de la gramínea en la masa del forraje, la relación lámina de la hoja/tallo, lámina de la hoja, tallo, material senescente y crecimiento. En los ensayos de la digestibilidad in vitro, el origen del inóculo mostró un efecto significativo en algunas variedades. Debido a las diferencias en los ensayos in vitro, se recomendó el uso de inóculos específicos de las especies para las evaluaciones de alimentos según el animal al que se destina. Asimismo, B. decumbens cv. Basilisk presentó la mejor digestibilidad in vitro (DMSiv y DFDNiv) en inóculo bovino, mientras que B. humidicola cv. Tupi tuvo mejor digestibilidad in vitro (DMSiv y DFDNiv) en inóculo ovino.

Abstract It was hypothesized that it is possible that inoculum from different ruminant species with different digestive abilities feeding from a certain forage may show different feed utilizations comparing to other ruminant species. Five Brachiaria grasses were evaluated: B. decumbens cv. Basilisk, B. decumbens access D70, B. humidicola cv. Tupi, B. humidicola cv. Common, and B. ruziziensis access R124, at two regrowth ages (21 and 42 d). Production, bromatological content, in vitro dry matter digestibility (ivDMD) and in vitro neutral detergent fiber digestibility (ivNDFD) were analyzed using bovine or ovine inoculums. The experiment used a 5 × 2 × 2 factorial design and found significant effects for grass variety and regrowth age. In addition, significant interactions from grass × age on dry matter, crude protein, neutral detergent fiber and acid detergent fiber of total sample and leaf blade were found. There were significant effect of grass variety and grass age on forage mass, leaf blade/stem ratio, leaf blade, stem, senescent material and growth. In vitro digestibility assays of inoculum source showed significant effect in some varieties. Due to differences in in vitro assays, it was recommended the use of species-specific inoculums for feed evaluations according to the animal it is intended for. Also, B. decumbens cv. Basilisk presented the best in vitro digestibility (ivDMD and ivNDFD) in bovine inoculum, whereas B. humidicola cv. Tupi had better in vitro digestibility (ivDMD and ivNDFD) in ovine inoculum.

Abstract High seed yield is a fundamental characteristic of apomictic and sexual hybrids of the genus Urochloa P. Beauv. (syn. Brachiaria (Trin.) Griseb.). It has been suggested that there is an association between polyploidy, the presence of meiotic irregularities, and low seed formation in this genus. The present study aimed to correlate these characteristics in Urochloa polyploid sexual interspecific hybrids in relation to the production of pure seeds. Segregational and non-segregational abnormalities were shown to led to cause the formation of tetrads with micronuclei, microcytes, polyads, and anomalous end products. The correlation between the percentage of meiotic abnormalities and the total production of pure seeds was negative and significant. To our knowledge, this is the first research with sexual polyploid hybrids from Urochloa and is relevant to identify hybrids with less frequent meiotic abnormalities and higher seed yield, with promising female parents for the breeding program.

Abstract The selection of sexual genitors in Urochloa decumbens breeding is dependent upon the performance of their progeny simultaneously for several traits. Thus, our objectives were to (i) compare the efficiency of indices to select genitors of U. decumbens, (ii) evaluate the genetic gains obtained through selection intensities, and (iii) evaluate the multivariate pattern of progenies through principal components analysis (PCA). For this purpose, 1415 hybrids from 75 progenies of full siblings were evaluated at Embrapa Beef Cattle (Brazil) using seven cuts for dry matter production, regrowth, protein, fiber, lignin, and percentage digestibility. Statistical analyses were performed using mixed models and PCA. The direct selection for dry matter production provided a 37.51% genetic gain. Agronomic traits using indices provided greater gains. Genitors selected using PCA Biplot were similar to selections using indices. Indices and PCA were proven to be an excellent tool to select multi-traits in U. decumbens.

Abstract Perennial grass hybrids of Urochloa are evaluated for at least two years during the screening stage trials (SS) and advanced trials (AD) in breeding programs, an expensive and time-consuming process. In this study, we aimed to evaluate the potential for early selection of cultivars in this breeding scheme. We used multiple measurements of agronomic and nutritive value traits of Urochloa humidicola and Urochloa decumbens in the SS, and Urochloa ssp. in the AD. Repeatability coefficient, genetic correlation, selection efficiency (SE), and Spearman correlations were estimated. The results indicated that reliable early selection could be applied, decreasing the evaluation period to one year and a half for SS, and to one year for AD. These results were confirmed by high genetic and rank correlations, and overall SE above 50%. This proposed change in the breeding scheme could save considerable time, labor, and resources and accelerate the release of improved cultivars.

ABSTRACT The objective of this two-year study was to evaluate live weight gain per animal and per area and their relationships with the characteristics of BRS Ipyporã (Brachiaria ruziziensis × Brachiaria brizantha) and Marandu (Brachiaria brizantha) pastures. A completely randomized block design was used with two treatments and four replicates. The grazing method was rotational stocking, with variable stocking rate. Stocking rate was adjusted twice a week during the grazing period (six or seven days) and post-grazing canopy height target of 15 cm. Animals were weighed every 28 days. Pastures were evaluated pre-grazing to estimate forage accumulation rate, forage mass (FM), leaf (LP) and stem (SP) percentages, and nutritive value. In the post-grazing, FM, LP, and SP were evaluated. Marandu palisadegrass pastures had greater FAR, pre-grazing FM, and hence, a greater SR when compared with BRS Ipyporã. However, compared with Marandu, BRS Ipyporã showed greater LP, leaf:stem ratio, crude protein, and in vitro organic matter digestibility, resulting in greater individual live weight gain. The lesser stocking rate in Ipyporã pastures was compensated, providing a greater individual live weight gain of steers, resulting in a similar live weight gain per area for the two cultivars. Thus, BRS Ipyporã is a good alternative for the diversification of pastures in the Cerrado region.

RESUMO: Objetivou-se avaliar os efeitos do nitrato de potássio, em diferentes concentrações e períodos de imersão, na superação da dormência de sementes de Brachiaria humidicola cv. ‘BRS Tupi’. Os experimentos, em número de quatro, foram realizados com diferentes lotes de sementes, em esquema fatorial (5x3+1) em diferentes períodos de armazenamento após a colheita, em que os tratamentos consistiram de imersão das sementes em soluções com diferentes concentrações de nitrato de potássio (0; 0,1; 0,3; 0,5 e 1% de KNO3), por três períodos de exposição (12, 24 e 48h), mais uma testemunha (sem tratamento), em delineamento inteiramente casualisado. As características avaliadas foram: curva de embebição, germinação, primeira contagem e índice de velocidade de germinação e viabilidade pelo teste de tetrazólio. Os tratamentos 0,1; 0,3; 0,5 e 1% de KNO3 ou água pura, com período de embebição por 12 horas, proporcionam germinação satisfatória das sementes armazenadas por, no mínimo, oito meses após a colheita. A partir de 24h de embebição das sementes ocorre protrusão radicular, enquanto para as sementes não tratadas a germinação satisfatória ocorre, no mínimo, a partir de 12 meses da colheita e, na maioria dos lotes, de 18 a 24 meses.

ABSTRACT: In this study, the aim was to determine the influence of potassium nitrate, using different concentrations and immersion times on the dormancy of the seeds of Brachiaria humidicola cv. ‘BRS Tupi’. Four experiments were performed adopting a factorial scheme (5x3+1) in different seed lots, for different post-harvest storage durations, during which the seeds were immersed in potassium nitrate solutions of different specific concentrations (0, 0.1, 0.3, 0.5 and 1% KNO3), for three exposure periods (12, 24 and 48h), plus one control (untreated), in a completely randomized design. The characteristics assessed included the imbibition curve, germination, first count and germination rate, as well as viability confirmed by using tetrazolium test. From the findings it was evident that treatments involving 0.1; 0.3; 0.5 and 1% KNO3 or pure water, with a 12 hour-soaking period enabled the stored seeds to germinate well for a minimum of eight months post harvest. Root protrusion was observed 24 hours post seed imbibition, whereas for the untreated seeds, satisfactory germination was observed from at least 12 months post harvest and, in most of the lots, between 18 and 24 months.

Abstract The breeding program Brachiaria developed by Embrapa Beef Cattle provides studies to obtain forage with agronomic characters desired by farmers. In this regard, in 2013 and 2014, a study was carried out in order to select the best Brachiaria decumbens intraspecific hybrids, which are superior in relation to production, forage nutritional value, and resistance to spittlebugs. Estimates of genetic parameters and gains with selection were carried out. It was found that there was significant variability between genotypes for all characters. Gain with selection (GS%) ranged from 12 to 324%, and the highest percentage was found for weight of pure seeds (PS) of seed collectors of the second harvest. For reproductive tillers (RT), C001 and R091 hybrids had better performance than the control, and this character may be considered as a parameter to estimate production of pure seeds before flowering starts.

RESUMO: Objetivou-se avaliar aspectos da fenologia reprodutiva, componentes do rendimento e qualidade de sementes do genótipo B4 de Brachiaria brizantha em função de doses de nitrogênio aplicado no pré-florescimento. O experimento foi conduzido na Embrapa Gado de Corte, em blocos casualizados, densidade de semeadura de 2,59kg SPV ha-1, em plantas de primeiro ano e em crescimento livre. Ureia foi aplicada no pré-florescimento nas doses 0, 25, 50, 75, 100, 125 e 150kg ha-1. O ciclo reprodutivo da planta foi de 225 dias, com florescimento tardio. Doses de N influenciaram o número de inflorescências totalmente emergidas, porcentagem de matéria seca, biomassa seca, número de espiguetas por racemo, produtividade de sementes puras, peso de mil sementes, germinação, índice de velocidade de germinação, viabilidade e germinação aos 10 meses da colheita. A produtividade máxima de sementes puras foi 144,8kg ha-1 para 50kg ha-1 N, com potencial biológico máximo, baseado nos componentes da produção de sementes de 456,27kg ha-1. As sementes apresentaram dormência elevada e redução na qualidade fisiológica nas maiores doses de N.

ABSTRACT: This study aimed to evaluate aspects of reproductive phenology, yield components and seed quality of the B4 genotype of Brachiaria brizantha in function of nitrogen doses applied at pre-flowering. The experiment was carried out at Embrapa Beef Cattle, in a randomized block design, with seeding density of 2.59kg SPV ha-1 in the first year, in free growth plants. Urea was applied at pre-flowering at doses of 0, 25, 50, 75, 100, 125 and 150kg ha-1. The reproductive cycle of the plant lasts 225 days, with late flowering. N doses influenced the following characteristics: number of fully expanded inflorescences, percentage of dry matter, dry biomass, number of spikelets per raceme, seed yield, weight of a thousand seeds, germination, germination speed index, viability and germination at 10 months after harvest. The maximum yield of pure seed was 144.8kg ha-1 for 50kg ha-1 N, with maximum biological potential, based on components of seed yield of 456.27kg ha-1. Seeds presented high dormancy and reduced physiological quality in higher N doses.

Abstract The objective of this study was to estimate genetic parameters for agronomic traits and nutritional value in intraspecific hybrids of B. decumbens. For this, a population of 1,415 hybrids was evaluated in field plots at Embrapa Beef Cattle in Campo Grande/MS/Brazil, with seven clippings in order to estimate field green weight (FGW); total dry matter (TDM); speed of regrowth (SR); tiller regrowth density (TRD); regrowth ability (REG); crude protein (CP); in vitro organic matter digestibility (IVD); neutral detergent fiber (NDF) and lignin (LIG). The statistical analyses were carried out using the mixed models methods. Genetic variability for all traits assessed was detected, and estimates of individual heritability were of medium to high magnitude, indicating the possibility of gains with selection. Significant genetic correlations were observed between FGW and TDM (0.99), TDM and SR (0.81), TDM and IVD (-0.71), TDM and LIG (0.71), and CP and IVD (0.70).

Abstract Tetraploid Brachiaria ruziziensis genotypes which reproduce sexually are essential for the breeding of other species of the Brachiaria genus which reproduce by apomixis. Aiming at studying the available phenotypic and genetic variability in the breeding population of B. ruziziensis, it was estimated the parameters heritability and genetic and phenotypic correlations between the traits associated with flowering, and the traits responsible for forage yield and nutritional quality. Seventeen traits in 1180 individuals from 59 open pollinated families were studied, and the data were analyzed by mixed model methods. Individuals with sparse flowering presented higher breeding values for total dry matter, yield, and total number of panicles per plant than individuals with early or late flowering. Considering breeding population differences on flowering behavior, on individual narrow sense heritability and on genetic correlations between flowering, agronomic quality and nutritional quality traits have to be considered in intrapopulation breeding and in intrapopulational recurrent selection.

Resumo: O objetivo deste trabalho foi identificar quais caracteres qualitativos poderão ser usados na seleção direta e indireta de genótipos de Urochloa brizantha, quanto ao teor de proteína bruta. Foram avaliados nove genótipos, em delineamento de blocos ao acaso, com duas repetições. Os caracteres qualitativos avaliados foram: volume de gás acumulado nas frações rápida e lenta, proteína bruta, fibras em detergentes neutro e ácido, celulose, lignina, sílica e digestibilidade in vitro da matéria orgânica. A digestibilidade in vitro da matéria orgânica é indicada tanto para a seleção direta quanto indireta de genótipos de U. brizantha com maior teor de proteína bruta.

Abstract: The objective of this work was to identify which qualitative characters can be used in the direct and indirect selections for high-protein content of Urochloa brizantha genotypes. Nine genotypes were evaluated in a randomized complete block design, with two replicates. The following qualitative traits were studied: volume of packed gas in fast and slow fractions, crude protein, acid and neutral detergent fibers, cellulose, lignin, silica, and in vitro digestibility of organic matter. The in vitro digestibility of organic matter is indicated for both direct and indirect selections of U. brizantha genotypes with higher crude protein content.

Resumo: Brachiaria decumbens tem grande importância no cenário nacional da pecuária de corte por apresentar alto potencial produtivo forrageiro e alta adaptabilidade a solos ácidos e de baixa fertilidade. Com o intuito de ser obter novas cultivares, híbridos intraespecíficos, previamente selecionados pelo programa de melhoramento de Brachiaria, foram avaliados nos anos de 2013 e 2014, quanto a caracteres fenológicos e potencial de produção de sementes por meio de seus componentes de produção, visando a obtenção de cultivares com características agronômicas satisfatórias de produção e de produtividade de forragem, com resistência às cigarrinhas-das-pastagens e boas produtoras de sementes. As estimativas de correlação fenotípica e análise de variância foram realizadas pelo software SAS 9.3. A partir dos resultados obtidos nos dois anos consecutivos, observou-se que, houve correlação entre número de perfilhos reprodutivos (PR) e peso de sementes puras (SP) nos canteiros do segundo ano de produção em nível de 70% (p<0,01), o que pode ser considerado como parâmetro para se estimar a produção de sementes puras antes do início do florescimento.

Abstract: Brachiaria decumbens has great importance in the national beef cattle scenario due to its high forage yield potential and high adaptability to acid soils and low fertility. In order to obtain new cultivars, intraspecific hybrids, previously selected by the Brachiaria breeding program, were evaluated in 2013 and 2014 for phenological characteristics and seed production potential through their production components, aiming to obtain cultivars with satisfactory production agronomic characteristics and forage yield, resistant to 'cigarrinhas-das-pastagens'(Tomaspia sp.) and good seed production. Estimates of phenotypic correlation and analysis of variance were performed using the SAS 9.3 software. From the results obtained in both consecutive years, it was observed that there was a correlation between the reproductive tiller number (RT) and the pure seeds (PS) weight in the seedbeds of the second year of production around 70% (p < 0.01), which can be considered as a parameter to estimate the production of pure seeds before the start of flowering.

ABSTRACT The objective of the present study was to evaluate live weight gain per animal and per area and its relationship with the characteristics of pastures of Brachiaria brizantha cv. Paiaguás and Piatã. A randomized blocks experimental design was used, with two treatments and six replicates. The experimental area was 8.0 ha, divided into twelve paddocks of 0.67 ha. The grazing method used was continuous stocking, with variable stocking rate. Three tester steers were used per paddock. Sward heights were measured once a week, and the stocking rate (SR) was adjusted using regulator steers to maintain the sward height at 30 cm. Pasture samples were collected once a month, and herbage accumulation rate (HAR), percentage of leaves (PL), leaf:stem ratio (LSR), and nutritive value (NV) were determined. Animals were weighed every 28 days. No differences between the two cultivars were observed during the wet season for any of the evaluated parameters. However, cv. Paiaguás presented higher HAR and, consequently, higher SR than cv. Piatã during the dry season. As a result of its higher regrowth, cv. Paiaguás pastures presented significantly higher PL, LSR, and NV and, consequently, significantly higher average daily live weight gain. These differences resulted in higher live weight gain per area for Paiaguás grass (695 kg/ha per year) than for Piatã grass (645 kg/ha per year). Thus, Brachiaria brizantha cv. Paiaguás is a good alternative to decrease the temporary forage shortage and for the diversification of pastures in the Cerrado biome region.

Resumo Objetivou-se avaliar híbridos intraespecíficos de Brachiaria decumbens para dois componentes da adaptação edafoclimática: vigor da raiz e resistência aoalumínio. Cem híbridos intraespecíficos e seus parentais foram avaliados em casa de vegetação. Os híbridos diferiram para ambos os caracteres, indicando a existência de variabilidade genética. Os parentais apresentaram desempenho semelhante para vigor da raiz, mas diferiram para resistência ao alumínio. Vinte e três e sete híbridos foram superiores a cultivar Basilisk para vigor da raiz e resistência ao alumínio, respectivamente, porém a maioria não foi coincidente em ambos os caracteres. A herança da resistência ao alumínio aparenta ser quantitativa, visto que a maioria dos híbridos apresentou um desempenho mediano, e poucos nos extremos. A estimativa da herdabilidade com base em médias de progênies para resistência ao alumínio (0,27) foi inferior a do vigor da raiz (0,69). A metodologia utilizada foi eficiente em discriminar e identificar híbridos superiores para adaptação edafoclimática.

Abstract The objective of this work was to evaluate hybrids of Brachiaria decumbens for root vigor and aluminum resistance as components of edaphic adaptation. One hundred intraspecific hybrids and their parents were evaluated in a greenhouse solution-culture. Significant differences for both traits indicate that there is genetic variability amongst hybrids. The parents had a similar performance for root growth, but differed significantly for aluminum resistance. Twenty three and seven hybrids were superior to cv. Basilisk for root vigor and aluminum resistance, respectively, but most of them were not coincident for both traits. Aluminum resistance seemed to vary quantitatively, since the majority of the hybrids were placed around the mean and fewer in the extremes. The estimate of heritability based on progeny means for aluminum resistance (0.27) was lower than for root vigor (0.69). The method used was efficient in discriminating hybrids, and identified the best ones for edaphic adaptation.

Resumo O objetivo deste trabalho foi estimar parâmetros genéticos para caracteres agronômicos e de resistência às cigarrinhas-das-pastagens em híbridos de Brachiaria decumbens e selecionar os de melhor desempenho. Trezentos e vinte e quatro híbridos foram avaliados em campo para caracteres agronômicos e em casa de vegetação para resistência às cigarrinhas-das-pastagens. Observou-se existência de variabilidade genética entre os híbridos para todos os caracteres analisados. As estimativas de herdabilidade entre médias de genótipos foram superiores a 0,52 para todos os caracteres agronômicos e de 0,98 para sobrevivência ninfal e 0,99 para duração do período ninfal. Híbridos com melhor desempenho em relação a cultivar Basilisk foram identificados para cada caráter individualmente e conjuntamente por meio de índices de seleção. A atribuição de pesos diferentes entre os caracteres nos índices de seleção não alterou significativamente o ranqueamento dos híbridos. Híbridos superiores foram selecionados para as próximas etapas do programa de melhoramento.

Abstract The objective of this work was to estimate genetic parameters for agronomic traits and resistance to spittlebugs in B. decumbens hybrids and to select the ones with best performance. For that, 324 hybrids were evaluated in field plots for agronomic traits and in the greenhouse for resistance to spittlebugs. Genetic variability amongst the hybrids was observed for all traits analyzed. The heritability estimates between genotypes means were higher than 0.52 for all agronomic traits and 0.98 and 0.99 for nymphal survival and nymphal period duration respectively. Hybrids with better performance than cultivar Basilisk for each individual trait were identified and also through a selection index combining all traits. Assigning weights to the different traits in the selection index did not significantly alter the rank for superior hybrids. Those were selected to continue on to the next phases of the breeding program.