No abstract

Resumo -O objetivo deste trabalho foi determinar a variabilidade genética e a expressão de caracteres de interesse forrageiro em espécies de Paspalum. Os experimentos foram conduzidos em diferentes locais e anos de cultivo, em delineamento de blocos ao acaso, com três repetições. Foram avaliados cinco acessos de P. nicorae e dois de P. guenoarum, além da cultivar Pensacola (P. notatum), utilizada como testemunha. Foram quantificados os seguintes caracteres: relação folha/colmo, índice de colheita e massa de matéria seca total, de folhas e de colmo. Tanto os efeitos principais (genótipos, anos e locais de cultivo) quanto a interação entre os fatores tiveram influência significativa sobre os caracteres avaliados. Os acessos avaliados apresentam variabilidade genética em caracteres de interesse forrageiro, bem como desempenho variável de acordo com o local e o ano de cultivo. A produção de matéria seca total e de folhas são os caracteres que mais contribuem para a detecção da variabilidade genética observada, independentemente do ano de avaliação.Termos para indexação: apomixia, espécie nativa, interação genótipo x ambiente, seleção. Genetic variability of forage traits in PaspalumAbstract -The objective of this work was to determine the genetic variability and the expression of traits of interest for forage production in species of Paspalum. The experiments were carried out in different locations and crop years in randomized block design with three replicates. Five accessions of P. nicorae and two of P. guenoarum were evaluated, besides the cultivar Pensacola (P. notatum), used as a control. The following traits were determined: leaf/stalk ratio; harvest index; and total, leaf, and stalk dray matter. Both main effects (genotype, years, and locations) and the interactions among factors had significant influence on the evaluated traits. The evaluated accessions showed genetic variability in traits of interest for forage production, and their performance varied according to the location and year of cultivation. Total and leaf dry matter production are the traits that most contribute to the detection of the observed genetic variability, regardless of the year of evaluation.

The Paspalum genus includes several species that are important for livestock in Rio Grande do Sul, such as P. notatum and P. guenoarum, typical of native pastures of the Pampa biome. The aim of this study was to investigate forage production and chemical composition of four ecotypes of these species in relation to the cv. 'Pensacola' (P. notatum). Ecotypes of P. guenoarum (Azulão and Baio) and P. notatum (André da Rocha and Bagual) and the cv. 'Pensacola' were evaluated for two years, during which four cuts/year were made. The work was carried out under field conditions at the Agronomic Experimental Station of the Federal University of Rio Grande do Sul (30°05'S; 51°39'W), in a completely randomized design. P. guenoarum stood out for higher productivity and greater tolerance to cold; the Azulão ecotype showed more autumn production in relation to the other ecotypes. Crude protein content ranged from 14 (Baio) to 15% ('Pensacola'); for neutral detergent fiber, the variation was 68 (Azulão) to 71% ('Pensacola') and for acid detergent fiber there was a variation of 38 ('Pensacola') to 43% (Baio). The data demonstrates the potential of native genotypes for use as cattle feeding in southern Brazil.

Brachiaria brizantha and Brachiaria decumbens constitute the two most widely used tropical forage species for cultivated pastures and support both beef and dairy cattle production in the tropics. Two apomictic cultivars -B. brizantha cv. ÔMaranduÕ and B. decumbens cv. ÔBasiliskÕ -cover more than 100 million hectares of cultivated pastures throughout Latin America and Southeast Asia. This paper discusses the cytogenetic data of the first successful attempt in obtaining interspecific hybrids between these two species. Artificial hybridization between two diploid (2n = 2x = 18) sexual accessions (B. brizantha, B105 · B. decumbens, D004) was performed in the greenhouse. Only three hybrids were recovered. One of them was treated with colchicine in tissue culture and two amphidiploid plants were obtained. Meiosis in the diploid genitors was quite normal, while in the diploid hybrid parental genome separation was observed together with some irregular chromosome segregation. Genome separation was also observed in several cells in the two 4n amphidiploid hybrids. In these, a high number of meiocytes with chromosomes chaotically spread in the cytoplasm was recorded during meiosis. The abnormalities observed compromised the meiotic products characterized by polyads. Chromosomes associated generally as bivalents but some association as quadrivalents in diakinesis in one of the amphidiploid hybrids indicates taxonomic proximity between these two species. Moreover, it indicates that introgression of desirable genes may be feasible between these two most important agronomic species of the genus.

ABSTRACT

For many decades, animal production in southern Brazil has been based on native forage grasses. Paspalum notatum Flügge (bahiagrass) is one of the most frequently used native grass in southern Brazil. The native germplasm of P. notatum is tetraploid and displays apomictic reproduction; hence, chromosome doubling of sexual diploid accessions is required to facilitate hybridization. The main goal of this study was to evaluate forage production and other agronomical evaluation of P. notatum intraspecific hybrids in order to obtain new varieties that could be registered and/or protected and launched as new cultivars in the future. Three tetraploid sexual genotypes were crossed with the ecotypes Bagual and André da Rocha. Biomass production (leaf, stem, and inflorescence fractions), plant growth habit, plant height, number of tillers, and frost damage were evaluated in the resulting hybrids. The general combining ability (GCA) and specific combining ability (SCA) were calculated for the six families generated. We evaluated 196 hybrids and the most productive yielded 42 % more total dry mass than the most productive parent (ecotype Bagual), and Bagual production was seven-fold higher than that of cultivar 'Pensacola'. The highest GCA values were observed for Bagual and Q4205. No correlation was observed between leaf coloration and the frost effect or regrowth in the following winter.Similarly, no correlation between plant growth habit and dry mass production was observed. The reproduction mode of the most productive hybrids are currently being analyzed in larger plots to identify apomictic and sexual genotypes for future registration and protection.

The objective of the study was to analyze the genetic variability at agronomic and molecular level of apomictic genotypes of the genus Paspalum obtained by interspecific crosses of Paspalum plicatulum (sexual famale genitor) and Paspalum guenoarum (apomictic male genitor) to predict promising combinations with the sexual genitor using characters related to forage production. The study was conducted in two environments in 2010 and 2011 in Eldorado do Sul and Augusto Pestana, State of Rio Grande do Sul, Brazil. The experiment followed a randomized block design with four replicates at both locations. Seven interspecific hybrids, the two genitors (sexual "4c-4x" P. plicatulum and apomictic cultivate "Rojas" P. guenoarum) and two native genotypes of Paspalum guenoarum and cultivate Pensacola of P. notatum were used. Analysis done inagronomic and molecular levels were able to detect genetic variability among interspecific hybrids of Paspalum. Moreover, the results suggested that the hybrids H12, H13 and H20 are recommended for further hybridizations with female sexual parent obtaining elite recombinant.

The goal of this study was to assess the variability of Paspalum plicatulum x P. guenoarum