S. C. L. Barrios

The value of improved pastures to Brazilian beef production

Abstract. Brazil is an agricultural country, with 190 Mha of pastures sustaining 209 million 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 50 Mha. 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 8 Mha 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 4 Mha. Improved pastures are thus a major asset in Brazil not only for the beef production chain but also for the dairy industry.

Performance of maize single-crosses developed from populations improved by a modified reciprocal recurrent selection

Maize (Zea mays L.) elite inbred lines developed from pedigree programs tend to be genetically related. Therefore, it is necessary to incorporate unrelated inbreds to those programs to allow the continued release of outstanding single-crosses. The objectives of this research were to compare the usefulness of a modified reciprocal recurrent selection procedure (MRRS) to improve populations to be used as sources of elite inbreds and outstanding single-crosses to integrate pedigree programs, and to investigate the effects of selection on the relative contribution of general (GCA) and specific combining (SCA) abilities to the single-crosses variation. Eight and six S3 lines from populations IG-3-C1 and IG-4-C1, respectively, selected from the first cycle of the MRRS program were crossed in a partial-diallel mating design, and the 48 experimental and five commercial single-crosses were evaluated in six environments. Grain yield mean of the experimental single-crosses (9.57 t ha1) did not differ from the commercial single-crosses (9.86 t ha1), and ten of the 48 experimental single-crosses could be released as cultivars because they compared favorably to the currently used single-crosses. Thus, one cycle of the MRRS procedure improved efficiently the populations allowing the development of outstanding single-cross, but additional cycles of selection should be carried out since none of the experimental single-crosses outperformed the highest yielding commercial single-cross. The relative contribution of the GCA over SCA may have been affected by the MRRS, since the SCA was more important than GCA for some of the traits assessed.

Characterization and selection of interspecific hybrids of Brachiaria decumbens for seed production in Campo Grande - MS

The breeding program Brachiaria developed by Embrapa Beef Cattle provides studies to obtain forage with agronomic characters desired by farmers. In this regard, in 2013 and 2014, a study was carried out in order to select the best Brachiaria decumbens intraspecific hybrids, which are superior in relation to production, forage nutritional value, and resistance to spittlebugs. Estimates of genetic parameters and gains with selection were carried out. It was found that there was significant variability between genotypes for all characters. Gain with selection (GS%) ranged from 12 to 324%, and the highest percentage was found for weight of pure seeds (PS) of seed collectors of the second harvest. For reproductive tillers (RT), C001 and R091 hybrids had better performance than the control, and this character may be considered as a parameter to estimate production of pure seeds before flowering starts.

Genetic mapping with allele dosage information in tetraploid Urochloa decumbens (Stapf) R.D. Webster reveals insights into spittlebug (Notozulia entreriana Berg) resistance

Urochloa decumbens (Stapf) R.D. Webster is one of the most important forage grasses in Brazilian beef production; therefore, genomic studies such as constructing molecular maps and defining the genetic architecture of relevant agronomic traits, are essential to understanding U. decumbens genetic structure and advancing breeding programs. The study objectives were to (i) obtain an integrated U. decumbens genetic map using molecular markers with allele dosage information, (ii) detect QTLs for spittlebug (Notozulia entreriana) resistance, and (iii) seek putative candidate genes involved in resistance/defense against pathogens. We used five pseudo-genome references to align GBS reads and selected 4,240 high-quality SNP markers identified in the Setaria viridis genome. Of these markers, 1,000 were distributed throughout nine homologous groups with a cumulative map length of 1,335.09 cM and an average marker density of 1.33 cM. The map contains SNP markers with different configurations for a tetraploid species. For the first time, this study detected QTLs for resistance to spittlebug, an important pasture insect pest, explaining between 4.66% and 6.24% of the variation. These QTLs had markers linked to putative candidate genes related to resistance/defense against pathogens. Because this is the first U. decumbens map to include SNP dosage data and QTL detection, it will be useful for future evolutionary studies, genome assembly, and other quantitative trait locus analyses in Urochloa spp. Moreover, the results might facilitate the isolation of spittlebug-related genes and help clarify the mechanism of spittlebug resistance. These approaches will improve selection efficiency and accuracy in U. decumbens molecular breeding. The GBS sequence data files supporting the conclusions of this article are in the process of submission to the NCBI Sequence Read Archive (SRA), with accession number SRP092493