Rosangela Maria Simeão

The value of improved pastures to Brazilian beef production

Abstract. Brazil is an agricultural country, with 190u2009Mha of pastures sustaining 209u2009million cattle. Fewer than 10% of the cattle are fattened in feedlots, whereas cattle reared on pastures have a competitive advantage for export, eliminating the risks presented by the mad cow disease (bovine spongiform encephalopathy) and considerations related to animal welfare. Brazil has been the world’s largest exporter of beef since 2004 and has the largest commercial herd in the world. In 2011, 16.5% of its production was exported, and the livestock sector contributed 30.4% of the gross national product from agribusiness and 6.73% of the total GNP. Many forage breeding programs, mainly at Embrapa, have contributed to the development of improved pastures, and cultivars of Brachiaria brizantha, B. decumbens, B. humidicola and Panicum maximum are the main pastures used in the country. All have apomictic reproduction, which means there are few cultivars occupying very large, continuous areas, thus suggesting a risk to the productive system. Such is the case of B. brizantha cv. Marandu, which occupies around 50u2009Mha. The Brazilian tropical forage seed industry is also important, and Brazil is the main seed exporter, supplying all Latin American countries. Due to pasture degradation, around 8u2009Mha is renovated or recovered each year. Forages are also used and planted each year in integrated crop–livestock and integrated crop–livestock–forest systems. Nowadays, these systems occupy 4u2009Mha. Improved pastures are thus a major asset in Brazil not only for the beef production chain but also for the dairy industry.

Avaliação genética em erva-mate pelo procedimento BLUP individual multivariado sob interação genótipo x ambiente

The objectives of this paper were to estimate genetic and phenotypic parameters and to predict breeding values for parents and provenances of Ilex paraguariensis. Eight provenances with 164 progenies were evaluated on three sites (Ivai, PR, Guarapuava, PR and Rio Azul, PR) for the trait leaf weight (LW). All the variance components, parameters and breeding values were obtained by REML/BLUP (restricted maximum likelihood/best linear unbiased prediction) procedure at the indi- vidual level, through multivariate analysis involving the three sites. The individual strict sense herita- bilities for the trait LW were 0.15 in Ivai, 0.62 in Guarapuava and 0.23 in Rio Azul, demanding more sophisticated selection methods in Ivai and Rio Azul. The provenance effect was significant in Ivai and Rio Azul, with intraclass phenotypic correlation of 0.13 in Ivai and 0.09 in Rio Azul. The provenances were more stable across sites than progenies with genetic correlation of 0.95 between the sites Ivai and Rio Azul. Genetic values for all provenances and parents in all sites were predicted for the trait LW. The best provenances are Barao de Cotegipe, Quedas do Iguacu, Cascavel and Ivai.

Genetic parameters of agronomic characters in Panicum maximum hybrids

This study was carried out with the objective of estimating the genetic parameters of agronomic traits in Panicum maximum hybrids. Genotypes obtained from the crosses between the sexual plants S10 and S12 and cultivars Tanzania and Mombasa were evaluated. The design was an incomplete blocks design with two replicates (clones) and 33 blocks. Each block was constituted by three lines or plots with nine plants each, which were evaluated in six harvests. All the characters presented low broad sense heritabilities for both the individual harvest and for the mean of harvests and a large difference between the heritability and the individual repeatability coefficient, which may be due to the high permanent environmental variance, mainly for forage dry matter and leaf dry matter. On the other hand, the percentage of leaves also presented low repeatability and permanent environmental variance. The genotypic coefficients of variation were high, except for leaf percentage, but they were also associated with high residual coefficients of variation. Both the broad sense heritabilities per harvest and for the mean of harvests were of moderate magnitude for the agronomic traits evaluated in hybrid individuals of P. maximum. On the other hand, there is variability for selection of important characters such as total and leaf dry matter yields and selection for leaf percentage needs a greater number of harvests to improve selection efficiency. The genotypes presented great variability for Bipolaris maydis leaf spot incidence and this character can be included in the P. maximum breeding program.

Potential of Panicum maximum as a source of energy.

The use of plant biomass as a source of energy presents many advantages, mainly that it is a renewable, clean source of energy. Many tropical grasses have excellent potential as energy crops. The main one in Brazil is Pennisetum purpureum (elephant grass) owing to its very high yields. However, it is vegetatively propagated, thus more difficult to establish than seed-propagated species. The use of Panicum maximum (guinea grass) is a possible alternative for use as a source of energy, due to its high yields as well as seed propagation. The objective of this research was to evaluate the potential of different P. maximum genotypes for use as energy crops, in comparison with elephant grass.

Variabilidade genética de acessos da cultivar 'BRS Bela' de Stylosanthes guianensis usando marcadores moleculares RAPD

Taxonomically Stylosanthes guianensis is divided in four botanical varieties: var. guianensis, var. pauciflora, var. canescens and var. microcephala. The BRS Bela cultivar is one of the two cultivars of this forage legume registered on Brazil, it is made up of a physical mixture of seeds of four accessions of unknown botanical varieties. The objective in this research was to characterize the genetic variability among four accessions of the cultivar BRS Bela and to determine its genetic relationship with others accessions of known botanical varieties, using the random amplified polymorphic DNA (RAPD) technique. Ten decamer primers were evaluated in 36 accessions, from the germoplasm bank of Embrapa Beef Cattle, of S. guianensis: 14 of the botanical variety pauciflora, 11 of var. guianensis, four of var. canescens, three of var. microcephala and the four accessions of cultivar BRS Bela. The amplified bands were analyzed as binary data and a matrix of genetic similarity was generated using the coefficient of Jaccard. Genetic dissimilarity data were utilized for clustering the accessions by not weighted pair-group method with arithmetical average (UPGMA) and Tocher methods. The mean genetic similarity within of the botanic varieties was of 0.72 for var. pauciflora, 0.63 for var. microcephala, 0.62 for var. canescens and 0.46 for var. guianensis. Among the four accessions of cultivar BRS Bela this mean was 0.62. Both methods of clustering generated similar results and showed a tendency to cluster the accessions of the same botanical variety. The accessions of cultivar BRS Bela were grouped with accessions of botanical variety guianensis. The results show that there is genetic variability within of the botanical varieties of S. guianensis and among the accessions of the cultivar BRS Bela and that there is a tendency to the clustering by botanical variety.

Selection of full-sib families of Panicum maximum Jacq under low light conditions 1

The silvopastoral system is a viable technological alternative to extensive cattle grazing, however , for it to be successful, forage grass genotypes adapted to reduced light need to be identified. The objective of this study was to select progenies of Panicum maximum tolerant to low light conditions for use in breeding programs and to study the genetic control and performance of some traits associated with shade tolerance. Six full-sib progenies were evaluated in full sun, 50% and 70% of light reduction in pots and subjected to cuttings. Progeny genotypic values (GV) increased with light reduction in relation to plant height (H) and specific leaf area (SLA). The traits total dry mass accumulation (DM) and leaf dry mass accumulation (LDM) had GV higher in 50% shade and intermediate in 70% shade. The GV of tiller number (TIL) and root dry mass accumulation (RDM) decreased with light reduction. The highest positive correlations were obtained for the traits H and RDM with SLA and DM; the highest negative correlations were between TIL and SLA and RDM, and H and LDM. The progenies showed higher tolerance to 50% light reduction and, among them, two stood out and will be used in breeding programs. It was also found that it is not necessary to evaluate some traits under all light conditions. All traits had high broad sense heritability and high genotypic correlation between progenies in all light intensities. There is genetic difference among the progenies regarding the response to different light intensities, which will allow selection for shade tolerance.