ABSTRACT
The search for alternatives to increase productivity and sustainability of livestock production in the Amazon region without increasing deforestation is challenging. Mixed pastures of grasses with forage peanut (Arachis pintoi) have shown positive economic impacts. However, gaps in the knowledge of the reproductive biology of A. pintoi have limited the development of new cultivars adapted to the environmental variations in the Brazilian Amazon. Pasture consortiums of Brachiaria humidicola with forage peanuts (cv. Mandobi) resulted in a 42% increase in weight gain productivity. New cultivars better adapted to the Amazon climate should bring even greater gains. We evaluated the mating system in twenty A. pintoi accessions, and approximately 40 offspring per accession genotyped with eight microsatellites (or markers). The parameters of genetic diversity and inbreeding, the outcrossing rate and coancestry were calculated. The observed heterozygosity was significantly higher and the fixation index was significantly lower in adults compared with the offspring. The crossing rate was variable among genotypes (2 to 80%), and the mean outcrossing rate was 36%. These results indicate that pollinator presence in pastures can influence gene flow in A. pintoi more than expected. Arachis pintoi presented a mixed mating system with a predominance of selfing, and families presented inbreeding and different levels of relatedness. New strategies of genotype conservation are needed to avoid pollinator-mediated crossing between accessions. (AU)
Subject(s)
Arachis , Sexual Behavior, Animal , Breeding , Amazonian Ecosystem , GenotypeABSTRACT
The objective of this study was to test the efficiency of preservation and maceration methods for Euterpe precatoria leaflet tissue to obtain genomic DNA for molecular studies. The leaflets of E. precatoria were collected in an experimental field at Embrapa Acre, Brazil. The study was conducted in a completely randomized design with 10 replicates, in a 12 × 2 factorial structure, with 12 storage treatments (fresh; lyophiliser 3 days; refrigerator 3, 5, and 7 days; silica gel 7, 10, 20, and 30 days; and transport buffer 3, 5, and 7 days) and two leaf tissue maceration methods (liquid nitrogen and the TissueLyser®). Statistically significant differences in the obtained DNA concentration were found between the maceration and storage treatments. The TissueLyser® macerator produced higher DNA concentrations when compared to liquid nitrogen. For the storage treatments, five groups were formed based on DNA concentration when macerated with the TissueLyser® and two groups when macerated with liquid nitrogen. The DNA concentrations ranged from 285.00 ng/µ L (7 days in transport buffer) to 702.00 ng/µ L (30 days in silica gel) when the leaflets were macerated with liquid nitrogen, and from 572.73 ng/µ L (30 days in silica gel) to 2,850.00 ng/µ L (3 days in lyophiliser) using the TissueLyser® macerator. The DNA purity (A260/A280 nm) varied from 1.30 to 1.70 when the leaflets were macerated with liquid nitrogen and from 1.30 to 1.90 with the TissueLyser® macerator. Despite the variations in leaf tissue preservation and DNA concentration, all treatments were effective for DNA isolation and it was possible to amplify genomic regions of microsatellite markers by PCR. It was concluded that leaflets of E. precatoria stored in a lyophiliser and processed with an automatic macerator resulted in satisfactory DNA for molecular studies.
O objetivo deste estudo foi testar a eficiência de métodos de preservação e maceração de tecidos de folíolos de Euterpe precatoria para obter DNA genômico para estudos moleculares. Os folíolos de E. precatoria foram coletados no campo experimental da Embrapa Acre, Brasil. O estudo foi conduzido em delineamento inteiramente casualizado com 10 repetições, em esquema fatorial 12 × 2, com 12 tratamentos de armazenamento (fresco; liofilizado 3 dias; geladeira 3, 5, e 7; sílica gel 7, 10, 20 e 30 dias e tampão de transporte 3, 5 e 7 dias) e dois tipos de maceração do tecido foliar (nitrogênio líquido e TissueLyser®). Para a variável concentração de DNA houve diferença estatística entre os tipos maceração e de armazenamento. O macerador TissueLyser® apresentou maiores concentrações de DNA quando comparado ao nitrogênio líquido.Para os tipos de armazenamento verificou-se formação de cinco grupos quando macerados TissueLyser® e dois grupos quando macerados com nitrogênio líquido. As concentrações de DNA variaram de 285,00 ng/µ L (7 dias em tampão de transporte) a 702,00 ng/µ L (30 dias em sílica gel) quando maceradas com nitrogênio líquido. Quando maceradas com macerador TissueLyser® variaram de 572,73 ng/µ L (30 dias em sílica gel) a 2.850,00 ng/µ L (3 dias em liofilizador). A pureza do DNA (A260/A280 nm) variou de 1,30 a 1,70 quando os folíolos foram macerados com nitrogênio líquido e de 1,30 a 1,90 quando macerados em macerador TissueLyser®. Apesar das variações na conservação e concentração dos tecidos foliares, todos os tratamentos foram eficazes para o isolamento do DNA e amplificaram regiões de marcadores microssatélites. Concluiu-se que folíolos de E. precatoria armazenados em liofilizador e macerados com macerador automático resultaram em DNA satisfatório para estudos moleculares.