RESUMO
Genetic, environmental, technological and financial resources are used differently in cattle herds that participate in the same breeding programme. The percentages of calves sired by sires within their own herd or from external herds vary across herds, as do the intensities of use of reproductive biotechnologies. These divergences may be related to differences in the indicators of genetic performance for economic traits. The aim of this study was to determine the factors related to herd structure and genetic resource utilization that exert the greatest influence on the genetic merit of seedstock herds within a Nellore breeding programme. The database comprised 21 factors, along with genomic-enhanced expected progeny differences (GE-EPDs) for growth, reproductive and carcass traits, as well as a selection index of animals from 128 herds. By combining principal component analysis and cluster analysis, we were able to group the herds. We identified statistically significant differences (p < 0.05) in the mean values of the factors, GE-EPDs and genetic trends among the groups of herds. Differences in the percentage of sires from external herds and in sire age between the groups of herds were the factors most associated with differences in mean GE-EPDs and genetic trends. Using young sires from other herds or lineages is an effective strategy in animal breeding. By enhancing genetic variability, this approach does not only improve the genetic quality of herds but also accelerates genetic progress in desired traits over time. Therefore, to ensure the success of this strategy, it is crucial that seedstock herds undergo a thorough selection process aimed at maximizing the genetic potential of future generations of beef cattle.
RESUMO
There is little information regarding the genetic diversity of native species aimed at identifying the best viable progenies for in situ and ex situ conservation. Furthermore, there is a lack of future forest improvement programs. We aimed to know the genetic diversity of 64 Peltophorum dubium (Spreng.) Taub. (Fabaceae) progenies. We determined this species' dendrometric characteristics, and when using multivariate techniques and cluster analysis, we verified the differences between the progenies and groups with less heterogeneity. The progeny and provenance test was installed in Dourados (Mato Grosso do Sul - MS), with seeds collected in three MS regions (Vale do Ivinhema, Serra de Maracaju, and Serra da Bodoquena) and in the micro-region of Lavras (Minas Gerais - MG). The experiment was conducted in an alpha lattice 8 x 8 with four repetitions. We found genetic variability among and within P. dubium populations for all height, diameter, circumference at breast height, volume, and basal area characters. We suggest that P. dubium populations have high genetic variability, which indicates possible genetic improvement through best progeny selection. The UPGMA and Tocher methods grouped the progenies into three and nine groups, respectively, in which the most divergent individuals come from MG and the Bonito region in MS. Based on morphological characters, P. dubium progenies identified as 45, 47, 49, 50, 55, and 59 from MG are the most promising, while progenies 6 and 9 were the least promising.
Informações quanto à diversidade genética de espécies nativas visando identificar melhores progênies viáveis para conservação in situ e ex situ, além de futuros programas de melhoramento florestal são incipientes. Objetivamos conhecer a diversidade genética de 64 progênies de Peltophorum dubium (Spreng.) Taub. (Fabaceae). Determinamos os caracteres dendrométricos dessa espécie, e ao utilizarmos técnicas multivariadas e análises de agrupamento verificamos as diferenças entre as progênies e grupos de menor heterogeneidade. O teste de progênies e procedências foi instalado em Dourados (MS), cujas sementes foram coletadas em três regiões de MS (Vale do Ivinhema, Serra de Maracaju e Serra da Bodoquena) e na microrregião de Lavras-MG. O experimento foi conduzido em alfa-látice 8 x 8, com quatro repetições. Constatamos variabilidade genética entre e dentro das populações de P. dubium para todos os caracteres altura, diâmetro, circunferência à altura do peito, volume e área basal. Sugerimos que as populações de P. dubium tem alta variabilidade genética, o que indicou possibilidade de melhoramento genético pela seleção das melhores progênies. Os métodos UPGMA e Tocher agruparam as progênies em três e nove grupos, respectivamente, em que os indivíduos mais divergentes são procedentes de MG e da região de Bonito em MS. As progênies de P. dubium de identificação 45, 47, 49, 50, 55 e 59, todas de MG, são as mais promissoras, enquanto que as progênies 6 e 9, foram as menos promissoras, baseando-se nos caracteres morfológicos.