-(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.