-(The seed coat as a modulator of seed-environment relationships in .abaceae). The seed coat is one of the main determinants of seed germination, vigor and longevity potentials. It is also intimately associated with temporal and spatial dispersion of seed germination in a large number of plant species. The understanding of its properties and characteristics may explain, anticipate or even allow the modification of seed performance under certain environmental conditions. There is a growing volume of evidence associating seed coat characteristics to specific seed problems. .or example, susceptibility to mechanical damage is related to lignin content of the seed coat, while seed longevity and tolerance to field weathering depends on seed coat integrity. Seed performance in many legumes has been associated with certain seed coat structures, such as the hilum, strophiole and micropyle. In soybean, permeability is also related with porosity, color, and cerosity, that affect seed vigor, storage potential, resistance to shrinking and fungi infection, and to susceptibility to imbibition damage. The understanding of these associations is necessary before genetic alterations through breeding for desirable characteristics and is fundamental for the development and improvement of seed pre-sowing treatments, production, handling and quality evaluation procedures, which may ultimately result in reduction of seed quality losses and increase the efficiency of agricultural production systems.RESUMO -(O tegumento como modulador das relações da semente com o ambiente em .abaceae). O tegumento é um dos principais condicionantes da germinação, do vigor e da longevidade de sementes. A compreensão da sua estrutura e propriedades pode contribuir para explicar, antecipar ou alterar o comportamento de sementes sob determinadas condições ambientais. Grande parte das características do tegumento está associada a problemas específicos apresentados pelas sementes. Assim, por exemplo, susceptibilidade a danos mecânicos está associada ao seu teor de lignina, enquanto que longevidade e potencial de deterioração no campo têm sido relacionados ao grau de permeabilidade do tegumento. Em leguminosas, o grau de permeabilidade da semente está associado ao comportamento de determinadas estruturas presentes no tegumento (hilo, estrofíolo, micrópila). Especificamente no caso da soja, a permeabilidade está também associada à porosidade, cor e cerosidade, que influenciam o vigor, o potencial de armazenamento, o grau de resistência ao enrugamento, à infecção por microorganismos, à danos por embebição, etc. A compreensão destas associações é necessária antes de qualquer tentativa de alteração via melhoramento genético de características indesejáveis, é fundamental ao desenvolvimento e aperfeiçoamento de práticas adequadas de manuseio, produção e de testes de avaliação de qualidade de sementes que poderão resultar na redução de perdas de qualidade de sementes e no aumento da eficiência dos sistemas de produção agrícolas.

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.

Turfgrass cultivation is a multi-purpose popular practice, associated with life quality of urban populations in consequence of its capability of providing safe, pleasant environments, suitable for recreational and sportive activities. Additionally, it plays relevant environmental functions. For these reasons, turfgrasses constitute an important segment of the agribusiness in many countries. In Brazil, the importance of this type of cultivation has increased in spite of the reduced number of available turfgrass cultivars. Research programs aiming the exploitation of his ample genetic diversity could promote Brazil to the forefront of this type of agriculture in the tropical world. In this work, we discussed and proposed degrees of relevance for different characteristics of grass plants destined for use as permanent ground coverage under a variety of Brazilian situations.

Since long lawns have been cultivated worldwide to perform a large variety of functions. Brazilian lawns have been constituted by a reduced number of species and cultivars. This work was developed with the purpose of estimating the potential of use as lawns presented by the members of a collection of accesses of native species of Paspalum and Axonopus (Poaceae). The following characteristics were evaluated: maximum vertical growth height, speed of soil cover, speed of regrowth, dry mass production, ornamental quality, weed encroachment and demand for mowing. Several accessions presented desirable characteristics and can therefore be included in programs aiming the development of cultivars for lawns intended for use in a variety of situations. The results here reported and discussed represent an experimental verification of the potential of the Brazilian flora to offer plants for use as lawns, reinforce the importance of native genetic resources and contribute to the continuity of research aimed at the development of this type of cultivars in Brazil.

Screening for resistance to insect pests is one of the early stages of grass breeding programs. Pasture spittlebugs are sap-sucking insects that potentially cause severe damage to turfgrasses, including the loss of functional quality and perenniallity. The Brazilian flora has a large number of grass species with wide morphological variability and adaptability to different soil and climate conditions that can potentially be used as lawns. However, no study has screened turfgrass genotypes for resistance to spittlebug attack. In this study, we evaluated the intra- and interspecific variability of 35 turfgrass genotypes in the genera Paspalum, Axonopus, and Zoysia for resistance to the pasture spittlebugs, Deois flavopicta (Stal) and Notozulia entreriana (Berg) (Hemiptera: Cercopidae), as measured by damage scores, densities of nymphs and adults, and level of antibiosis resistance. Genotypes were grouped into three groups using cluster analysis and principal component analysis: GroupI had genotypes associated with low damage scores and high density of adult spittlebugs; GroupII had genotypes with intermediate damage scores and low density of nymphs and adults; and GroupIII was formed by genotypes with high damage scores and high nymph density. Intra- and interspecific genotypic variability was related to antibiosis resistance and morphological variation among genotypes with some indicating nonpreference resistance and others indicating tolerance resistance. Our results indicate that besides antibiosis resistance studies, it is essential to evaluate the morphological variability of grass genotypes when screening for resistance to insects. Further studies are needed to elucidate the intraspecific variability of Paspalum notatum Flüggé genotypes for resistance to spittlebug attack.

Microsatellite (SSR) markers were developed for the following tropical forage species, using accessions available from the plant genetic resources (PGR) collections held by EMBRAPA (Brazilian Agricultural Research Corporation): Brachiaria brizantha, B. humidicola, Panicum maximum, Paspalum spp., Stylosanthes capitata, S. guianensis, S. macrocephala, Calopogonium mucunoides and Centrosema spp. The markers were used to analyze population structure and genetic diversity, evolution and origin of the genetic variability in the center of origin, mating systems and genetic resources in EMBRAPA's germplasm bank. The results shed light on the amount of genetic variation within and between populations, revealed the need in some cases for further plant collection to adequately represent the species in PGR collections, allowed us to assemble core collections (subsets of the total collections) that should contain most of the available diversity and (in the case of the legumes) showed the need to avoid unwanted outcrossing when regenerating conserved material. The data will allow plant breeders to better select accessions for hybrid production, discriminate between genotypes and use marker-assisted selection in breeding programs. Our results will also underpin the construction of genetic maps, mapping of genes of agronomic interest and numerous other studies on genetic variability, population structure, gene flow and reproductive systems for the tropical forage species studied in this work. ResumenSe desarrollaron marcadores microsatélite (SSR) para las siguientes especies forrajeras tropicales, usando accesiones de germoplasma disponibles en las colecciones de recursos genéticos mantenidas por EMBRAPA (Empresa Brasileira capitata, S. guianensis, S. macrocephala, Calopogonium mucunoides y Centrosema spp. Los marcadores se usaron para analizar la estructura de las poblaciones y su diversidad genética; la evolución y el origen de la variabilidad gené-tica en los respectivos centros de origen; los sistemas reproductivos; y los recursos genéticos en el banco de germoplasma de EMBRAPA. Los resultados arrojaron luz sobre la magnitud de la variación genética dentro de y entre poblaciones; revelaron la necesidad, para algunas especies, de incrementar las colecciones de germoplasma y así obtener una adecuada representación de las especies en las colecciones de recursos genéticos; permitieron establecer colecciones núcleo (subconjuntos de colecciones grandes), representativas de la diversidad genética disponible en las respectivas colecciones completas; y mostró, para las leguminosas, el riesgo de cruzamientos no deseados al multiplicar semilla de las accesiones conservadas. La información obtenida facilitará a los fitomejoradores la selección de accesiones para la generación de híbridos, la distinción entre genotipos, y el uso de la selección asistida por marcadores en programas de fitomejoramiento. Los resultados también ayudarán para la construcción de mapas genéticos, el mapeo de genes de interés agronómico y otros estudios...

These results suggest that the characterized markers have enough discriminatory potential to be used in genetic characterizations of Paspalum taxa, which are based on an understanding of their mating systems and genetic structure, as well as in understanding the evolutionary processes involved in the evolution of groups of Paspalum.

RESUMOOs gêneros Paspalum e Axonopus encontram-se entre as principais gramíneas de estação quente utilizadas para gramados. A propagação via sementes contribui para diminuir o custo de implantação, além de manter as características exatas do genótipo da planta mãe, por se tratar de espécies apomíticas. O objetivo deste trabalho foi avaliar o potencial de produção de sementes de dezessete acessos de gramíneas das espécies Paspalum notatum, P. lepton, P. lividum e Axonopus parodii. O experimento foi conduzido no município de Capão do Leão, Rio Grande do Sul, em blocos casualizados, com quatro repetições. As variáveis avaliadas foram: número de inflorescências por área, número de flósculos por inflorescência e potencial de produção de sementes (PPS). Para mensurar o potencial de produção de sementes dos acessos propõe-se a equação: PPS = nº de flósculos por inflorescência x nº de inflorescências por m 2 . Houve efeito de ano, acesso e interação entre anos e acessos para número de inflorescências por área e potencial de produção de sementes. Para a variável número de flósculos por inflorescência, não houve efeito de ano. A produção potencial da safra 2013/2014 variou de 19152,00 a 135062,70 sementes m -², destacando-se o acesso PN 09 da espécie P. notatum e na safra 2014/2015 a produção potencial variou de 9973,75 a 81536,75 sementes m -², destacando-se o acesso PN 11 da espécie P. notatum. Os acessos PN 11, PN 09, PN 10 e AP 01 estiveram no terço superior no ranking de produtividade potencial nas duas safras, e a grama-batatais no terço inferior. Existe interação genótipo-ambiente para todas as características avaliadas. Entretanto, existem acessos que apresentam produção potencial de sementes consistentemente superior à testemunha grama-batatais, tendo maior potencial para a exploração na implantação de gramados por sementes. Palavras-chave: Paspalum notatum, P. lepton, P. lividum, Axonopus parodii, inflorescência, apomixia. ABSTRACT Potential of grass seed production for new lawnsThe Paspalum and Axonopus genera are among the main warm season grasses used for lawns. The seed propagation contributes to the decrease of the cost of establishment, besides maintaining the exact characteristics of the mother plant genotype, because they are apomictic species. The objective of this work was to evaluate the seed production potential of seventeen grass accesses of the species Paspalum notatum, P. lepton, P. lividum and Axonopus parodii. The experiment was conducted at Capão do Leão, Rio Grande do Sul State, Brazil, in a randomized block design, with four replications. The evaluated variables were: number of inflorescences per area, number of florets per inflorescence and seed production potential (SPP). In order to measure the seed production potential of the accesses, the equation proposed is: SPP = number of florets per inflorescence x number of inflorescences per m 2 . There were year, access and interaction between years and accesses effect for the traits number of inflorescences per area and seed production potential...