Pattern analysis of the diversity of morphological plant attributes and herbage yield in a world collection of white clover (Trifolium repens L.) germplasm characterised in a summer moisture stress environment of Australia

Information on the variation available for different plant attributes has enabled germplasm collections to be effectively utilised in plant breeding. A world sourced collection of white clover germplasm has been developed at the White Clover Resource Centre at Glen Innes, New South Wales. This collection of 439 accessions was characterised under field conditions as a preliminary study of the genotypic variation for morphological attributes; stolon density, stolon branching, number of nodes. number of rooted nodes, stolon thickness, internode length, leaf length, plant height and plant spread, together with seasonal herbage yield. Characterisation was conducted on different batches of germplasm (subsets of accessions taken from the complete collection) over a period of five years. Inclusion of two check cultivars, Haifa and Huia, in each batch enabled adjustment of the characterisation data for year effects and attribute-by-year interaction effects. The component of variance for seasonal herbage yield among batches was large relative to that for accessions. Accession-by-experiment and accession-by-season interactions for herbage yield were not detected. Accession mean repeatability for herbage yield across seasons was intermediate (0.453). The components of genotypic variance among accessions for all attributes, except plant height, were larger than their respective standard errors. The estimates of accession mean repeatability for the attributes ranged from low (0.277 for plant height) to intermediate (0.544 for internode length). Multivariate techniques of clustering and ordination were used to investigate the diversity present among the accessions in the collection. Both cluster analysis and principal component analysis suggested that seven groups of accessions existed. It was also proposed from the pattern analysis results that accessions from a group characterised by large leaves, tall plants and thick stolons could be crossed with accessions from a group that had above average stolon density and stolon branching. This material could produce breeding populations to be used in recurrent selection for the development of white clover cultivars for dryland summer moisture stress environments in Australia. The germplasm collection was also found to be deficient in genotypes with high stolon density, high number of branches high number of rooted nodes and large leaves. This warrants addition of new germplasm accessions possessing these characteristics to the present germplasm collection

Análise de trilha dos componentes do rendimento de sementes de trevo-branco Path analysis in white clover seed yield components

Objetivou-se, por meio de uma análise de trilha para rendimento de sementes em trevo-branco, obter informações básicas para utilização em estratégias de manejo para maior produção de sementes e maior ressemeadura natural, proporcionando assim condições para maior persistência da espécie na pastagem. Foram analisadas as seguintes variáveis: botões florais, número de inflorescências, número de inflorescências maduras, número de legumes/inflorescência, peso de 100 sementes e rendimento de sementes. A variável que mais se correlacionou com o rendimento de sementes foi o número de inflorescências maduras (r = 0,91) e essa correlação ocorreu praticamente apenas pelo seu efeito direto. Nas demais variáveis, destacou-se o número de botões florais, com coeficiente de correlação alto (r = -0,55) e efeitos indiretos sobre os demais componentes. O número de inflorescências maduras parece ser a principal característica a ser considerada na busca de maior produção de sementes em trevo-branco.<br>The objective of this study was, by using a path analysis of seed yield in white clover, to obtain basic information for use in management strategies for higher seed production and higher natural reseeding and greater persistence of the species in the pasture. The following variables were analyzed: number of flower buds, number of inflorescences, number of mature inflorescences, number of legumes/inflorescence, weight of 100 seeds and seed yield. The variable most correlated with seed yield was the number of mature inflorescences (r = 0.91), and this correlation occurred almost only due to its direct effect. Among the other variables, the number of flower buds also had a high correlation coefficient (r = 0.55) and indirect effects on the other components. The number of mature inflorescences appeared to be the main characteristic to be considered when searching for a higher seed production in white clover

Florescimento e produção de sementes de Lotus subbiflorus Lag. cv. El Rincón Flowering and seed production of Lotus subbiflorus Lag. cv. El Rincón

Objetivou-se com este trabalho avaliar a dinâmica do florescimento e o potencial de produção de sementes de Lotus subbiflorus Lag. cv. El Rincón. Por meio de amostragens semanais realizadas entre 13/11/2008 e 4/2/2009, estudaram-se as variáveis número de botões florais, número de inflorescências, número de flores, número de legumes totais, peso de mil sementes e produção de sementes. O delineamento experimental utilizado foi de blocos casualizados com os tratamentos arranjados como níveis de um fator experimental, constituído pelas datas após a semeadura. Dessa forma, o experimento foi realizado com dois blocos e doze unidades experimentais por bloco. A produção de sementes de L. subbiflorus no Sul do Brasil tem problemas decorrentes do florescimento contínuo, o que dificulta a colheita. A produção máxima obtida foi de 63,2 kg/ha em janeiro de 2009 (4372 graus-dia). O peso de mil sementes e o número de legumes foram as características que mais se correlacionaram com a produção de sementes. A emissão constante de botões florais contribui negativamente sobre os demais componentes da produção de sementes.<br>The aim of this work was to evaluate the dynamic of the flowering and the Lotus subbiflorus Lag. Cv. "El Rincón"seed production potential. The variables studied through weekly samples from 11/13/2008 to 02/04/2009 were: number of flower buds, number of inflorescences, number of flowers, number of total legumes, weight of 1000 seeds and seed production. The experimental design used randomized blocks with treatments arranged as levels of an experimental factor, defined by the dates after seeding. The experiment was conducted with two blocks and twelve experimental units per block. Lotus subbiflorus seed production, in the South Brazil, presents problems caused by continuous flowering, difficulting to harvesting. The maximum production obtained was 63.2 kg/ha in January 2009 (4372 degree days). The weight of 1000 seeds and the number of legumes were the characteristics that most related to seed production. The constant emission of flower buds contributes negatively on the other components of seed production

Caracterizações morfológica e agronômica e divergência genética em germoplasma de trevo-branco Agronomic and morphological characterizations and genetic divergence on white clover germplasm

Objetivou-se caracterizar a variabilidade existente e estimar a divergência genética de uma coleção nuclear de trevo-branco formada por 78 acessos. Dezessete plantas de cada acesso foram caracterizadas com base em nove parâmetros (oito morfológicos e um agronômico): estatura das plantas, hábito de crescimento, intensidade de florescimento, comprimento de estolão, número de nós por estolão, comprimento dos entrenós, diâmetro de estolão, produção total de MS e área foliar por planta. Pela estimativa da distância de Mahalanobis, os acessos 1 (PI 195534) e 10 (PI 419325) apresentaram a maior distância (45,4) e os acessos 58 (PI 180491) e 68 (PI 197830), a menor distância (0,19). A área foliar foi a característica com maior contribuição relativa para divergência genética (24%), seguida pela estatura da planta (20%), pela intensidade de florescimento (19%) e pela produção total de MS (15%). A análise de correlação linear simples entre as variáveis mostrou correlação positiva e significativa entre estatura e área foliar (0,92), assim como entre comprimento de estolão e comprimento de entrenós (0,90).<br>This work aimed to evaluate morphological features of the white clover core collection obtained from the United States Department of Agriculture (USDA), represented by 78 accessions, in order to characterize the existent morphological variability and to estimate the genetic divergence, using nine characters (eight morphological and one agronomic). Seventeen plants from each access were evaluated individually at the Experimental Station of the Universidade Federal do Rio Grande do Sul in Eldorado do Sul and characterized in relation to the following characters: plant height, growth habit, flowering intensity, stolon length, node number per stolon, internode length, stolon diameter, total dry matter yield and leaf area per plant. Using the estimate of Mahalanobis' distance, the results showed that the accessions 1 (PI 195534) and 10 (PI 419325) presented the greatest distance (45.4), while the accessions 58 (PI 180491) and 68 (PI 197830) presented the smallest distance (0.19). The leaf area was the character with the largest individual relative contribution to the genetic divergence (24%), followed by plant height (20%), flowering intensity (19%) and total dry matter yield (15%). There was a positive and highly significant correlation between plant height and leaf area (0.92) and also between stolon length and internode length (0.90)