Construction of Microsatellite-Enriched Libraries for Tropical Forage Species and Characterization of the Repetitive Sequences Found in \u3cem\u3eBrachiaria Brizantha\u3c/em\u3e

The Brazilian cattle herd comprises 185 million animals fed with about 177 million hectares of native and cultivated pastures (IBGE, 2002). Of the grass species used for forage in Brazil, the African genus Brachiaria is the most widely planted, followed by Panicum, which also has an African origin. Legumes of the Stylosanthes genus, native to the South America, have emerged in the last few years as potential forage species for use with the grasses. These forage species have been bred at Embrapa Beef Cattle and the breeding programs have shown the need for more genetic information including the use of molecular markers. The objectives of this work were to construct microsatellite-enriched genomic libraries for 5 species of Brachiaria (B. brizantha, B. decumbens, B. dictioneura, B. humidicola and B. ruziziensis), for P. maximum and for S. capitata, and to characterize the microsatellites found in B. brizantha

Molecular Genetic Variability, Population Structure and Mating System in Tropical Forages

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 analyse population structure and genetic diversity, evolution and origin of the genetic variability in the centre 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

Selection efficiency in Brachiaria hybrids using a posteriori blocking

This paper compares the efficiency of Brachiaria hybrid clone selection by either traditional analysis or aposteriori blocking, to adequately consider the effect of lower competition in the border rows of the experimental plots (bordereffect). Results demonstrated that a posteriori blocking improved selection and the reliability of the genotypic evaluation. Ofthe ten best clones, four did not coincide in the two approaches. The ranking was altered as well, which demonstrated that theindication of the five best clones, selected to proceed to pasture trials based on the traditional evaluation, was misleading.This paper confirms the usefulness of a posteriori blocking. Furthermore, the results revealed the need to impose moreeffective competition on plants in the border rows to avoid erroneous selection when conducting evaluations for agronomicperformance in Brachiaria trials

Molecular genetic variability, population structure and mating system in tropical forages

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