Trifolium argentinense Speg. is an amphicarpic species that occurs naturally in native pastures of Rio Grande do Sul, southern Brazil. Amphicarpy is a rare mode of reproduction in which aerial and subterranean seeds are produced by the same individual. In the present paper, we compare morphology, anther number, pollen viability, seed production and mode of reproduction of T. argentinense flowers, and comment on the life strategy of the species. Plants grown from aerial seeds and from the regrowth of storage roots of aerial plants had longer stolons and a larger plant diameter than did those grown from subterranean plants. Plants grown from seeds were also taller than plants grown from storage roots. More resources were allocated to subterranean reproduction in plants of subterranean origin than in those of aerial origin. Aerial flowers produced more seeds, presented more anthers and produced more pollen grains than did the subterranean ones. T. argentinense is a versatile species, self- and cross-pollinated, consistent with the values of high polymorphism information content. T. argentinense adopts the ‘pessimistic strategy’ (early allocation of energy to large subterranean propagules), common in amphicarpic species when growing in disturbed habitats, such as the native pastures of Rio Grande do Sul, where intense grazing and trampling, as well as long seasonal dry spells, may periodically destroy the aerial plants, thus assuring survival by germination of subterranean seeds and regrowth of storage roots.

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.

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ResumoTendo em vista inúmeros problemas fitossanitários que vêm acometendo a citricultura brasileira, a diversificação de porta-enxertos é uma necessidade prioritária. Híbridos de porta-enxertos estão sendo desenvolvidos por programas de melhoramento genético de citros, os quais devem ser avaliados quanto a características morfológicas e de produção. Por esse motivo, o objetivo deste trabalho foi caracterizar folhas e frutos, determinar o número de embriões por semente e avaliar a taxa de poliembrionia de três porta-enxertos híbridos: citranges 'Fepagro C 13', 'Fepagro C 37' e 'Fepagro C 41' e compará-los a três porta-enxertos já utilizados na sustentação dos pomares de citros: Trifoliata, citrumelo 'Swingle' e citrange 'Troyer'. Pouca variação foi observada na caracterização morfológica das folhas, porém na caracterização dos frutos foram verificadas diferenças. Destacam-se os citranges 'Fepagro C 13' e 'Fepagro C 37' que produziram, na média, muitas sementes por fruto, ou seja, 24,2 e 35,0, sendo muitas viáveis, 19,2 e 21,2 e estas portando bom número de embriões, 5,0 e 3,1, além de altas taxas de poliembrionia, 84 e 92% respectivamente. Os resultados obtidos com os dois híbridos demonstram que eles possuem bom potencial para serem utilizados como plantas doadoras de sementes para porta-enxertos de citros.Palavras-chave: citricultura, porta-enxertos alternativos, morfologia de folhas e frutos. Morphological characterization, embryo number determination and polyembriony taxes in three citrus hybrid rootstocks AbstractDue to several phytosanitary problems that affect Brazilian citriculture, diversification of rootstocks is a priority. Hybrid root-stocks are being developed by citrus genetic breeding programs, and those hybrids must be evaluated regarding morphological characteristics and yield. Therefore, the objective of the present paper was to characterize leaves and fruits, to determine embryo number per seed and to evaluate polyembriony rates of three hybrid rootstocks: citranges 'Fepagro C 13', 'Fepagro C 37' and 'Fepagro C 41', comparing then to three other rootstocks currently used in citrus orchards Trifoliata, citrumelo 'Swingle' and citrange 'Troyer'. Little morphological variation was found in leaves but, for fruits, some differences were observed, especially in citranges 'Fepagro C 13' and 'Fepagro C 37' that produced, in average, many seeds per fruit 24.2 and 35.0, many of them viable, 19.2 and 21.2 and with a good number of embryos 5.0 and 3.1, respectively, besides presenting high polyembriony taxes, 84% and 92%, respectively. The results show that these two hybrids have a good potential to be used as seed donor plants to citrus rootstocks.

Tetraploid citrus rootstocks may present different morphological characteristics and growth when compared to diploid ones. This worked aimed at comparing morphological characteristics and height growth of diploid and tetraploid plants from the rootstocks 'Swingle' citrumelo [C. paradise Macf. x Poncirus trifoliate (L.) Raf], citrange 'Troyer' (C. sinensis (L.) Osb. x P. trifoliata) and citranges 'Fepagro C 13' and 'Fepagro C 37' [C. sinensis cv. Pêra x P. trifoliata] during twelve months. Diploid (2n=18) and tetraploid (2n=36) plants originated from the same seed were identified, cultivated and evaluated every 45 days regarding color, height, petiole length, leaf length and central leaflet width. Significant differences were observed for the evaluated characteristics: the average of petiole length was 1.78 cm in the diploid and 0.99 cm in the tetraploid plants; the average of leaf length was 2.32 cm in the diploid and 2.95 cm in the tetraploid plants; the average of central leaflet width was 1.33 cm in the diploid and 1.69 cm in the tetraploid plants. Moreover, tetraploid plants had darker and thicker leaves than the diploid ones. Variation regarding height was observed and the diploid plants presented higher growth than the tetraploid ones. As tetraploid plants are smaller, have a slow height growth and wider and longer leaves.Key words: Citrus, morphology, leaf color, height, dwarfing.Comparação entre porta-enxertos cítricos diploides e tetraploides: Caracterização morfológica e avaliação do crescimento Resumo Porta-enxertos cítricos tetraploides podem apresentar características morfológicas e desenvolvimento diferenciados comparados a plantas diploides. Este trabalho teve como objetivo avaliar características morfológicas e o crescimento em altura de plantas diploides e tetraploides dos porta-enxertos citrumelo Swingle [C. paradisi Macf. x Poncirus trifoliata (L.) Raf], citrange Troyer [C. sinensis (L.) Osb. x P. trifoliata] e dos citranges Fepagro C 13 e Fepagro C 37 (C. sinensis cv. Pêra x P. trifoliata) por um período de 12 meses. Plantas diploides (2n=18) e tetraploides (2n=36) oriundas da mesma semente foram identificadas, estabelecidas e avaliadas a cada 45 dias quanto a cor, altura, comprimento do pecíolo, da folha e largura do limbo do folíolo central. Diferenças significativas foram observadas nos caracteres avaliados: a média do comprimento do pecíolo nas plantas diploides foi de 1,78 cm e, nas tetraploides, de 0,99 cm; a média do comprimento das folhas nas diploides foi de 2,32cm e nas tetraploides de 2,95 cm; a média de largura dos folíolos centrais das folhas das plantas diploides foi de 1,33 cm e, nas tetraploides, de 1,69 cm; além disso, as plantas tetraploides apresentaram folhas com coloração mais escura e mais espessas do que as das diploides. Variações foram observadas na altura, com as plantas diploides apresentando maior crescimento que as tetraploides. Portanto, plantas tetraploides apresentam menor tamanho, crescimento em altura mais lento e folhas mais largas e compridas.Palavr...

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