Reproduction mode and apospory expressivity of selected hybrids of Paspalum notatum Flügge

Paspalum notatum Flüggé (bahiagrass) is the most important forage grass in the native grasslands of southern Brazil; the native germplasm is tetraploid and apomictic. Breeding to produce cultivars has been possible due to chromosome doubling of sexual diploid accessions, allowing hybridizations with apomictic genotypes, generating progenies with variability for agronomic traits and segregating for reproduction mode. The aim of this study was to determine the reproduction mode of selected hybrids derived from intraspecific crosses through cytoembryological analysis and to evaluate the level of apospory expres¬sivity. Eighty one tetraploid hybrids corresponding to 21 families of sexual and apomictic parents were generated and 28 most productive plants based on their superior agronomic performance in the field were evaluated. Sixteen hybrids were reproduced sexually and 12 of them were highly apomictic or facultative apomictic. Sexual hybrids may be used for further crosses in the breeding program while highly apomictic plants produce uniform progeny and become candidates of new cultivars to promote pasture diversification

Dissimilaridade entre ecótipos de Andropogon lateralis submetidos a diferentes frequências de desfolha e alturas de corte

Andropogon lateralis Nees is a native grass of southern Brazil and is one of the most frequent specie found in native grasslands. The species is widely distributed and has a high degree of phenotypic plasticity, which makes it highly adaptable to different edaphoclimatic conditions and management. This study aimed to evaluate the behavior of twelve ecotypes of A. lateralis, collected in different regions of the state of Rio Grande do Sul and cut to three different heights and subjected to two different defoliation frequencies. From September to February, the ecotypes were evaluated for total dry matter, leaf and stem yields. In addition, total, vegetative and reproductive tillers and plant height were measured. These characteristics are important for the selection of superior genotypes in terms of genetic variability and forage production. Total dry matter and leaf dry matter are characteristics with agronomic importance and they showed the highest correlation (r = 0.77), enabling an indirect selection for one of these characteristics. The natural selection of plants resulted in distinct structural, morphological and productive characteristics with heterogeneity that allows the selection and grouping according to the characteristics, ecotypes with superior agronomic characteristics can be included in breeding programs.Andropogon lateralis Nees é uma gramínea nativa do sul do Brasil e uma das espécies mais frequentes na flora dos campos nativos da região. Possui ampla distribuição e alto grau de plasticidade fenotípica, tornando-o adaptável as condições edafoclimáticas e a práticas de desfolha. Este estudo teve como objetivo avaliar a dissimilaridade entre doze ecótipos de A. lateralis N., coletados em diferentes regiões do Rio Grande do Sul, submetidos a duas frequências de desfolha e três alturas de corte. No período de setembro a fevereiro, os ecótipos foram avaliados quanto à produção de matéria seca total, de lâminas foliares e de colmo. Além disso, foram medidos o número de perfilhos totais, vegetativos e reprodutivos e a altura das plantas. Essas características são importantes para a seleção de genótipos superiores em termos de variabilidade genética e produção de forragem. A matéria seca total e a matéria seca foliar são características com importância agronômica e apresentaram a maior correlação (r = 0,77), possibilitando uma seleção indireta para uma dessas características. A seleção natural das plantas resultou em características estruturais, morfológicas e produtivas distintas com uma heterogeneidade que permite a seleção e agrupamento de acordo com as características, ecótipos com características agronômicas superiores podem ser incluídos em programas de melhoramento

Acúmulo de forragem em híbridos de grama-forquilha em dois ambientes distintos no Sul do Brasil

The native grasslands of southern Brazil have sustained livestock farming for many years; however, decline in pasture areas has led to the loss of genetic diversity of forage species.The development of forage grass cultivars adapted to different environments, will contribute to forming new cultivated pastures or recovering degraded areas.The aim of this study was to assess the herbage accumulation of selected intraspecific hybrid progenies of bahiagrass (P. notatum Flügge) in two different environments(Depressão Central and Campanha region)to estimate their agronomic value. The results indicated variability for the main forage traits studied(leaf dry mass, stem dry mass, inflorescence dry mass, total drymass, leaf: stem ratio,plant height and population density of tillers).All the hybrids producing more forage mass than the ‘Pensacola’ cultivarin the municipality of Eldorado do Sul and the majority also superior in the municipality of São Gabriel.Theproductionof leaves in the forage was correlated withtotal dry mass (84%), suggesting that genotype selection for forage massalso selected for production of leaves. The selected hybrids should be indicated for new steps of assessment within the P. notatumbreeding program.As pastagens nativas do Rio Grande do Sul (sul do Brasil), sustentam a pecuária há muitos anos; no entanto, o declínio em áreas de pastagens tem levado à perda da diversidade genética das espécies forrageiras e o desenvolvimento de cultivares de gramíneas forrageiras adaptadas a diferentes ambientes contribuirá para a formação de novas áresa de pastagens cultivadas ou recuperação de áreas degradadas. O objetivo deste trabalho foi avaliar o acúmulo de forragem de uma progênie híbrida intraespecífica selecionada de grama forquilha (Paspalum notatum Flügge) em dois ambientes distintos (Depressão Central e Campanha)para estimarseu valor agronômico.Os resultados indicaram variabilidade para as principais características forrageiras estudadas(massa seca das folhas, massa seca do caule, massa seca da inflorescência, massa seca total, relação folha:caule, altura daplanta e densidade de perfilhos) com todos os híbridos produzindo mais massa de forragemdo que a cultivar ‘Pensacola’no município de Eldorado do Sul e a maioria também superior no município de São Gabriel. A produção de folhas foi a característica mais correlacionada com a massa seca total(84%), sugerindo que a seleção de genótipos para massa de forragem também selecionou para a produção de folhas.Os híbridos selecionados poderão ser indicados para novas etapas de avaliações dentro do programa de melhoramento de P. notatum

Agronomic evaluation of Paspalum notatum Flügge under the influence of photoperiod

The objective of this study was to evaluate the influence of photoperiod on the forage yield by ecotypes and intraspecific hybrids of P. notatum. Tetraploid ecotypes from the United States Department of Agriculture and the National University of the Northeast in Argentina, in addition to six intraspecific hybrids, totaling 19 ecotypes, were assessed. The materials evaluated were subjected to an extended photoperiod (14 h of light) and natural photoperiod from July 2011 to October 2012. The experimental design was a completely randomized factorial scheme of 19 × 2 (ecotypes × photoperiod) consisting of five replicates. The materials were influenced differentially by the variation in photoperiod, with one group showing high sensitivity, whereas another, smaller group, was insensitive to this factor. The use of materials with differentiated responses to photoperiod in different climatic regions can be an important tool to increase forage yield of Paspalum notatum

Desempenho forrageiro de híbridos de Paspalum obtidos por meio de cruzamentos interespecíficos

The goal of this study was to assess the variability of Paspalum plicatulum x P. guenoarum interspecific hybrids in terms of agronomic performance and their tolerance to cold conditions, as well as to estimate the correlation of different phenotypic characters associated with forage production. Twenty hybrids plants were used, besides one access P. guenoarum, one of P. plicatulum and the cultivar ‘Pensacola’ (P. notatum). Assessments were performed on individual plants, in a completely randomized design with five repetitions. Paspalum genotypes presented variability in total dry matter, leaf dry mass, leaf: stem ratio, and tolerance to cold. We suggest selection of the hybrids 08Q01 and 08Q44 for new stages within a forage improvement program. Estimates of phenotypic correlation may aid in the selection of genotypes with better agronomic traits.O objetivo deste estudo foi avaliar a variabilidade de híbridos interespecíficos de Paspalum plicatulum x P. guenoarum por meio do desempenho agronômico e tolerância ao frio, bem como estimar as correlações fenotípicas de diferentes caracteres ligados à produção de forragem. Foram utilizados 20 híbridos, um acesso de P. guenoarum, um de P. plicatulum e a cultivar ‘Pensacola’ (P. notatum). As avaliações foram realizadas em plantas individuais, em delineamento completamente casualizado, com cinco repetições. Os genótipos de Paspalum apresentam variabilidade para massa seca total, massa seca de folhas e relação folha: colmo e na tolerância ao frio. É possível selecionar os híbridos 08Q01 e 08Q44 para novas etapas dentro de um programa de melhoramento de forrageiras. As estimativas de correlações fenotípicas podem auxiliar na seleção de genótipos com caracteres agronômicos superiores

Multivariate analysis reveals genetic diversity in Paspalum notatum Flügge

The objective of this study was to evaluate 94 Paspalum notatum genotypes over two growing seasons to estimate genetic dissimilarity through agronomic traits and the distance between genotypes. This information is used to create an ideotype from the best averages obtained for the set of characteristics evaluated. Seven apomitic, three sexual, and 81 hybrid genotypes were compared with native genotypes “André da Rocha”, “Bagual”, and cultivar “Pensacola” as controls. There is genetic variability in P. notatum for the studied characteristics, and distinct genotypes with superior characteristics can be used in new combinations between apomictic and sexual plants to obtain hybrids. The characters with the greatest relative contribution to the dissimilarity between the genotypes were tiller density, stem dry mass, and leaf dry mass yield. Thus, these characteristics are suitable criteria to infer genetic distance studies in P. notatum. The selection index based on the ideotype is an auxiliary tool in the breeding process. The ideotype must be based on characteristics of interest according to the objective of the breeding program, as well as on the breeder’s prior knowledge in relation to culture

Genetic parameters, prediction of gains and intraspecific hybrid selection of Paspalum notatum Flügge for forage using REML/BLUP

Genetic improvement of native forage species is a sustainable alternative for maximizing livestock production. Paspalum notatum Flügge is the most important forage grass in the native grasslands of southern Brazil, with substantial potential available for further genetic improvement. The objective of this study was to quantify a range of genetic parameters and predict yield gains in a population of P. notatum intraspecific hybrids. Results indicated intraspecific hybrids of P. notatum had high magnitudes of heritability in the broad and average sense of genotype, plus high selective accuracy and genetic variation for all forage characteristics evaluated. This indicated REML/BLUP can contribute useful information for plant selection in future plant breeding programs. The genetic material studied showed high genetic variability for forage production. Analysis indicated hybrids 336, 332, 437, 132 and male parent ‘30N’ should be included in new crosses to increase the dry matter production of P. notatum. Parents need to be selected from different groups in order to maximize genetic variability and heterosis. In addition, these parents must be included in diallel crosses. The results obtained in this study provide important information for the future breeding of improved P. notatum cultivars for commercialization

ESTIMATIVA DA CONVERSÃO EM PRODUTO ANIMAL A PARTIR DO USO DE Avena strigosa Schreb. SUBMETIDA A DIFERENTES FONTE S E DOSES DE NITROGÊNIO

The objective of this study was to evaluate the agronomic and economic response of black oat pasture (cv. Embrapa 29 Garoa) submitted to different nitrogen fertilization sources and doses. The experimental design used was a randomized block design, arranged in a factorial scheme: two sources of nitrogen x five fertilization doses x three cuts. Three hundred results obtained demonstrated that black oat crop responds in productive potential from different sources and doses of nitrogen fertilization, impacting differently on the animal product. The choice of fertilization dose within the different sources of nitrogen will depend on the efficiency of nitrogen utilization in fodder production and its conversion to animal production, coupled with the product remuneration and costs involved with pasture implantation. The application of urea as nitrogen source provided greater production of dry matter per cut in black oat culture when compared to ammonium sulfate. The highest efficiencies in the use of nitrogen were obtained by applying 45 kg ha-1 of urea and ammonium sulfate. Black oat culture responds biologically to the nitrogen fertilization dose of 90 kg N ha-1. The applications of 45 kg of N ha-1 in the form of urea and 23 kg ha-1 of ammonium sulfate were economically feasible under the conditions in which the study was carried out.O objetivo do presente estudo foi avaliar a resposta agronômica e econômica da pastagem de aveia preta (cv. Embrapa 29 Garoa) submetida a diferentes fontes e doses de fertilização nitrogenada. O delineamento experimental utilizado foi o de blocos ao acaso, organizado em esquema fatorial: duas fontes de Nitrogênio x cinco doses de fertilização x três cortes. Trezentos resultados obtidos demonstraram que a cultura da aveia preta responde em potencial produtivo a partir de diferentes fontes e doses de fertilização nitrogenada, impactando de maneira diferenciada sobre o produto animal. A escolha da dose de fertilização dentro das distintas fontes de Nitrogênio depende da eficiência de utilização do Nitrogênio em produção de forragem e a sua conversão em produção animal, aliado à remuneração do produto e custos envolvidos com a implantação da pastagem. A aplicação de ureia como fonte de Nitrogênio proporcionou maior produção de matéria seca por corte na cultura de aveia preta quando comparado ao sulfato de amônio. As maiores eficiências de utilização de nitrogênio foram obtidas com a aplicação de 45 kg ha-1 de ureia e sulfato de amônio. A cultura de aveia preta responde biologicamente até a dose de fertilização nitrogenada de 90 kg de N ha-1. As aplicações de 45 kg de N ha-1 na forma de ureia e 23 kg ha-1 de sulfato de amônio foram economicamente viáveis nas condições em que o estudo foi realizado