The NPGS-USDA core collection with 85 accessions of red clover, an important forage species, is little described. The goal of the present study was to evaluate the diversity of a set of accessions from the core collection at the morphological and molecular level in order to extract some valuable accessions for Brazilian red clover breeding programs. Twentyone morphological traits, collected in field and greenhouse in South Brazil, and seven SSR markers were used to describe 57 accessions from the U.S. core collection and one population cultivated in Southern Brazil. Variation between accessions was large for most of the 21 morphological traits. A cluster analysis based on the morphological traits revealed five distinct clusters that separated the populations according to flowering earliness, as already described, but also according to persistency, growth habit and dry matter productivity. Over seven SSR loci, the number of alleles averaged 11.1 alleles per locus. Genetic diversity measured with SSR markers was high, with a mean expected heterozygosity of 0.86. An analysis of molecular variance revealed that the largest proportion of variation (83.6%) resided at the within population level. Although the molecular markers also separated accessions into five clusters, there was no coincidence between the composition of groups found with morphological and molecular data. Use of genetic diversity in breeding programs requires to use the most promising populations, to combine positive traits such as persistency and forage yield, and probably to use within population variation to detect valuable genotypes that could be used as parents of synthetic varieties.

BackgroundPaspalum (Poaceae) is an important genus of the tribe Paniceae, which includes several species of economic importance for foraging, turf and ornamental purposes, and has a complex taxonomical classification. Because of the widespread interest in several species of this genus, many accessions have been conserved in germplasm banks and distributed throughout various countries around the world, mainly for the purposes of cultivar development and cytogenetic studies. Correct identification of germplasms and quantification of their variability are necessary for the proper development of conservation and breeding programs. Evaluation of microsatellite markers in different species of Paspalum conserved in a germplasm bank allowed assessment of the genetic differences among them and assisted in their proper botanical classification.ResultsSeventeen new polymorphic microsatellites were developed for Paspalum atratum Swallen and Paspalum notatum Flüggé, twelve of which were transferred to 35 Paspalum species and used to evaluate their variability. Variable degrees of polymorphism were observed within the species. Based on distance-based methods and a Bayesian clustering approach, the accessions were divided into three main species groups, two of which corresponded to the previously described Plicatula and Notata Paspalum groups. In more accurate analyses of P. notatum accessions, the genetic variation that was evaluated used thirty simple sequence repeat (SSR) loci and revealed seven distinct genetic groups and a correspondence of these groups to the three botanical varieties of the species (P. notatum var. notatum, P. notatum var. saurae and P. notatum var. latiflorum).ConclusionsThe molecular genetic approach employed in this study was able to distinguish many of the different taxa examined, except for species that belong to the Plicatula group, which has historically been recognized as a highly complex group. Our molecular genetic approach represents a valuable tool for species identification in the initial assessment of germplasm as well as for characterization, conservation and successful species hybridization.

Soil acidity and aluminum (Al) toxicity are major problems limiting performance of alfalfa (Medicago saliva L.) in many parts of the world, but neither an effective screening procedure nor a tolerant cultivar is available. The objective of this study was to evaluate different screening methods for selection of acid soil tolerant alfalfa germplasms in the greenhouse during 1991-1994. The general screening methods included selection in unlimed soil, selection in unlimed soil containing a limed germination layer, selection for either tolerance or sensitivity to acid soil stress with Al toxicity in tissue culture, selection in unlimed soil with tandem selection for Al tolerance in tissue culture, and selection in unlimed soil containing a limed, fertilized germination layer with tandem selection for Al tolerance in tissue culture. All selected populations and checks were evaluated during 1994 in greenhouse cups containing the following soil treatments: (i) cups filled with unlimed soil, (ii) cups filled with limed soil, and (iii) cups filled with unlimed soil containing a germimation layer of limed soil. Most of the selected populations possessed better root and shoot growth than the original base population (GA-TE) in unlimed soil, but only the population selected in unlimed soil showed better root and shoot growth in unlimed soil with a limed germination layer. No population had poorer performance than GATE in limed soil. Selection in cell culture for Al toxicity tolerance did not improve tolerance per se, but selection for Al sensitivity enhanced sensitivity. In terms of success, resources, and time, screening in unlimed soil was the most effective method to improve acid soil stress tolerance.

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.

Several species of the genus Paspalum L. are important forages, due to quality, productivity and tolerance to environmental stresses. Chromosome numbers, meiotic configurations and pollen fertility were evaluated in a collection of 85 accessions of Paspalum notatum Flügge and in seven accessions of Pensacola (P. notatum var saurae). All P. notatum accessions were tetraploid, with 2n = 4x = 40, except one diploid accession, considered as an escape of Pensacola. All Pensacola plants had 2n = 2x = 20. Meiotic configurations at diakinesis and metaphase I varied among tetraploid accessions, from plants with only bivalents to plants with high frequency of quadrivalents. Pollen fertility varied from 82.5 to 95.9% among diploid accessions and from 72.4 to 97.9% among the tetraploid. Due to the apomictic mode of reproduction of tetraploid P. notatum, meiotic irregularities can be maintained by the plants without harming their propagation. At the same time, pollen fertility should be high enough to assure endosperm development, since the species is pseudogamous. Wild diploid P. notatum populations, apart from the endemic P. notatum var saurae are very rare. From a plant breeding point of view, all the examined tetraploid accessions are potentially male-fertile and could be used as males in crosses. Key words: apomixis, chromosome numbers, meiotic configurations, plant breeding, pollen fertility DADOS CITOGENÉTICOS PARA ACESSOS DEPaspalum notatum FLÜGGE RESUMO: Muitas espécies do genus Paspalum L. são importantes forragens, devido à qualidade, produtividade e tolerância para o stress ambiental. Números cromossômicos, configurações meióticas e fertilidade do pólen foram analisados em uma coleção de 85 acessos de Paspalum notatum Flügge e sete acessos de Pensacola (P. notatum var saurae). Todos os acessos de P. notatum eram tetraplóides, com 2n = 4x = 40, com exceção de um diplóide, considerado como escape de Pensacola. Todas as plantas de Pensacola examinadas tinham 2n = 2x = 20. Foi verificada variação entre os acessos tetraplóides quanto às configurações cromossômicas em diacinese e metáfase I, desde plantas com apenas bivalentes até aquelas com alta freqüência de quadrivalentes. A fertilidade do pólen variou de 82,5 a 95,9% entre os acessos diplóides e de 72,4 a 97,9% entre os tetraplóides. Devido ao modo de reprodução apomítico de P. notatum tetraplóide, irregularidades meióticas podem ser mantidas sem prejuízo da propagação. Ao mesmo tempo, a fertilidade do pólen deve ser suficientemente alta para assegurar a formação do endosperma, já que a espécie é pseudogâmica. Diplóides silvestres de P. notatum, além do endêmico P. notatum var saurae são muito raros. Do ponto de vista do melhoramento, todos os tetraplóides são potencialmente macho-férteis e poderiam ser utilizados como genitores masculinos em cruzamentos. Palavras-chave: apomixia, números cromossômicos, configurações meióticas, melhoramento genético, fertilidade do pólen

Paspalum notatum is a forage grass recognized as one of the major constituents of the native grasslands in the New World. The knowledge of the genetic diversity and structure of P. notatum populations is fundamental for the conservation and germplasm management of this species. About 11 microsatellite markers were isolated from P. notatum and characterized in 25 accessions. The average number of alleles per locus was 7.9 and the PIC ranged from 0.36 to 0.89. The data demonstrated that the most of markers are suitable to detect polymorphism and to study the genetic diversity in the P. notatum species. Moreover, the transferability of these microsatellite were tested on other three congeneric species.

RESUMOPaspalum notatum Poaceae é uma importante espécie forrageira com ampla ocorrência no sul do Brasil, sendo constituída de biótipos sexuais (diplóides) e apomíticos (tetraplóides, ocasionalmente tri e pentaplóides). Este trabalho teve por objetivo a avaliação agronômica e a análise da persistência em uma coleção de acessos de P. notatum. Avaliaram-se 52 acessos de P. notatum, a cultivar comercial Pensacola e dois biótipos de P. guenoarum, Baio e Azulão. As avaliações foram realizadas em plantas individuais, em delineamento completamente casualizado, com cinco repetições durante os anos de [2008][2009]. Houve variação na produção de forragem dos diferentes acessos, sendo que a maioria dos acessos de P. notatum apresentou elevadas produções de matéria seca (de 469 g planta -1 a 109 g planta -1 de matéria seca de forragem total (MSFT)) ao serem comparados com a cultivar Pensacola (27 g planta -1 de MSFT). Os acessos 48N, 95N, 30N e V4 obtiveram as maiores produções (469, 380, 258 e 237 g planta -1 de MSFT, respectivamente), além de apresentarem persistência ao inverno da região. Conclui-se que a coleção avaliada pode ser de grande importância em futuros estudos de melhoramento genético com P. notatum. Palavras-chave:Forrageira, grama-forquilha, melhoramento genético. Agronomic evaluation and persistence analysis in a collection of Paspalum notatum Flügge (Poaceae) accessions ABSTRACTPaspalum notatum is an important forage species widely occurring in Southern Brazil, consisting of sexual (diploid) and apomitic (tetraploid, occasionally tri and pentaploid) biotypes. This work has the objective to perform an agronomic characterization and persistence analysis of a collection of P. notatum accessions. Fifty two accessions of P. notatum, the commercial cultivar Pensacola and two biotypes of P. guenoarum, Baio and Azulão were evaluated. The assessments were performed in individual plants, in a completely randomized design, with five replicates, during the years of 2008-2009. There was variation for forage production among the different accessions, with the majority of the accessions of P. notatum showing high dry matter yield (ranging from 469 g plant -1 to 109 g plant -1 of total forage dry matter (TFDM)) when compared to the cultivar Pensacola (27 g plant -1 of TFDM). The accessions 48N, 95N, 30N and V4 showed the highest yields (469, 380, 258 and 237 g plant -1 of TFDM) and also persistence to the winter in the region. It was concluded that the collection analyzed can be important in futures studies for P. notatum genetic improvement.

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