Chromosome diversity in Dasypyrum villosum, an important genetic and trait resource for hexaploid wheat engineering.

BACKGROUND AND AIMS: Dasypyrum villosum (2n = 2x = 14) harbours potentially beneficial genes for hexaploid and tetraploid wheat improvement. Highly diversified chromosome variation exists among and within accessions due to its open-pollination nature. The wheat-D. villosum T6VS·6AL translocation was widely used in breeding mainly because gene Pm21 in the 6VS segment conferred high and lasting powdery mildew resistance. However, the widespread use of this translocation may narrow the genetic base of wheat. A better solution is to utilize diversified D. villosum accessions as the genetic source for wheat breeding. Analysis of cytological and genetic polymorphisms among D. villosum accessions also provides genetic evolution information on the species. Using cytogenetic and molecular tools we analysed genetic polymorphisms among D. villosum accessions and developed consensus karyotypes to assist the introgression of beneficial genes from D. villosum into wheat. METHODS: A multiplex probe of repeats for FISH, GISH and molecular markers were used to detect chromosome polymorphisms among D. villosum accessions. Polymorphic signal block types, chromosome heterogeneity and heterozygosity, and chromosome polymorphic information content were used in genetic diversity analysis. KEY RESULTS: Consensus karyotypes of D. villosum were developed, and the homoeologous statuses of individual D. villosum chromosomes relative to wheat were determined. Tandem repeat probes of pSc119.2, (GAA)10 and the AFA family produced high-resolution signals and not only showed different signal patterns in D. villosum chromosomes but also revealed the varied distribution of tandem repeats among chromosomes and accessions. A total of 106 polymorphic chromosomes were identified from 13 D. villosum accessions and high levels of chromosomal heterozygosity and heterogeneity were observed. A subset of 56 polymorphic chromosomes was transferred into durum wheat through wide crosses, and seven polymorphic chromosomes are described in two newly developed durum-D. villosum amphidiploids. CONCLUSIONS: Consensus karyotypes of D. villosum and oligonucleotide FISH facilitated identification of polymorphic signal blocks and a high level of chromosomal heterozygosity and heterogeneity among D. villosum accessions, seen in newly developed amphiploids. The abundant genetic diversity of D. villosum and range of alleles, exploitable through interploid crosses, backcrosses and recombination (chromosome engineering), allow introduction of biotic and abiotic stress resistances into wheat, translating into increasing yield, end-use quality and crop sustainability.

Genetic structure and connectivity analysis in a large domestic livestock meta-population: The case of the Pura Raza Español horses.

The Pura Raza Español (PRE) is an autochthonous Spanish horse population distributed in 65 countries and managed by a single association. Since 1960s, breeding animals have been steadily exported to other countries to establish local subpopulations. We analysed the genetic structure of a PRE horse meta-population (MP) of 215,500 animals from countries with at least 80 active animals (27 countries comprising 77% of the total animals in the complete pedigree). Genotypes from active animals (59% of the total animals in the complete pedigree) were also studied. Genetic analysis of the MP was performed using classical parameters such as inbreeding (F), coancestry, founder contribution, effective number of founders/ancestors (fe/fa) and gene flow between countries. Results showed that the MPF coefficient decreased in the last two decades (1990-2013), indicating an explicit management against F. Founder contribution to genetic variability across countries mainly came from females (73.6%). In general, unbalanced contributions of founders reflected the high loss of genetic diversity along generations (fe/fa as low as 32/19 for the whole MP). Despite this differential contribution, the proportional contribution to the global diversity of each country was similar. The highest within-country coancestry value corresponded to Cuba (0.1509), being the only country with highly inbred individuals (over 12%), and the lowest value corresponded to Spain (0.0574). These results should help to avoid further declines in genetic variability and increases in F levels, especially in small countries like Cuba. In parallel, only nine countries presented descendants in a single population, suggesting a common origin for all countries and/or a substantial exchange of genetic material between populations. Spain and the US showed the highest gene flow rates. These results support the need of a coordinated management strategy, especially promoting the exchange of genetic material to increase the effective population size and maintain the levels of genetic diversity in the PRE horse population.

The genetic diversity and structure of 18 sheep breeds exposed to isolation and selection.

The phylogenetic layout of the genotyped (30 microsatellite) 18 sheep breeds in this study demands and provides the opportunity to evaluate both neutral and adaptive components of genetic diversity in a naturally and artificially selected and subdivided sheep population. Seven Pramenka strains from Bosnia and Herzegovina and Croatia characterized by a very low intensity of artificial selection, preserved the highest neutral genetic variability. Eight central and north-western European breeds under considerable artificial isolation and selection preserved the lowest genetic variability. Only combinations of various phylogenetic parameters offer a reasonable explanation for underlying evolutionary forces working in the investigated island and mainland sheep breeds under variable natural and artificial selection. More than 60% of total genetic, diversity was allocated to virtually unselected Pramenka strains, and an additional 25% to native moderately selected Graue Gehoernte Heidschnucke and intensively selected Ostfriesische Milchschafe. Some economically very important breeds and strains did not contribute to a pool with maximal genetic diversity, while they play an important role in the cultural heritage of respective countries.

Comparison of pooled semen insemination and single colony insemination as sustainable honeybee breeding strategies.

Instrumental insemination of honeybees allows for two opposing breeding strategies. In single colony insemination (SCI), all drones to inseminate a queen are taken from one colony. In pooled semen insemination (PSI), sperm of many genetically diverse drones is mixed and queens are fertilized from the resulting drone pool. While SCI allows for maximum pedigree control, proponents of PSI claim to reduce inbreeding and maintain genetic variance. Using stochastic simulation studies, we compared genetic progress and inbreeding rates in small honeybee populations under SCI and PSI. Four different selection criteria were covered: estimated breeding values (EBV), phenotypes, true breeding values (TBV) and random selection. Under EBV-based truncation selection, SCI yielded 9.0% to 44.4% higher genetic gain than PSI, but had vastly increased inbreeding rates. Under phenotypical or TBV selection, the gap between SCI and PSI in terms of genetic progress narrowed. Throughout, PSI yielded lower inbreeding rates than SCI, but the differences were only substantial under EBV truncation selection. As a result, PSI did not appear as a viable breeding strategy owing to its incompatibility with modern methods of genetic evaluation. Instead, SCI is to be preferred but instead of strict truncation selection, strategies to avoid inbreeding need to be installed.

Prioritization of Appearance over Health and Temperament Is Detrimental to the Welfare of Purebred Dogs and Cats.

Fashions in the appearance of purebred dogs and cats are encouraged by celebrity culture, social media, and online impulse buying. The popularity of characteristics perceived as cute, quirky, and anthropomorphic has driven increasingly exaggerated breed features appealing to aesthetics rather than health. 'Hypertypes' of some breeds have emerged that take a breed's distinctive appearance to extremes beyond the intended interpretation of breed standards. This has severe, direct and indirect health and welfare consequences. Extreme conformations are associated with chronic health conditions including brachycephalic obstructive airway disorder, ocular, dental, skin, and musculoskeletal disorders. Puppy and kitten farms and illegal traders that meet the demand for hypertypes are associated with poor husbandry that neglects the physical, behavioral, and mental health of parents and offspring. A multidimensional approach involving collaboration between breeders, geneticists, owners, veterinarians, kennel clubs, cat fanciers' associations, animal charities, the academic and research communities, commercial enterprises, and governments is needed to safeguard breeds and tackle these challenges. There are many ongoing initiatives by national kennel clubs and global partnerships to educate pet owners and support responsible pet ownership and sustainable breeding. The resounding message is that health, temperament, and well-being must be prioritized over appearance.

The Potential of Instrumental Insemination for Sustainable Honeybee Breeding.

Mating control is crucial in honeybee breeding and commonly guaranteed by bringing virgin queens to isolated mating stations (IMS) for their nuptial flights. However, most breeding programs struggle to provide sufficiently many IMS. Research institutions routinely perform instrumental insemination of honeybees, but its potential to substitute IMS in breeding programs has not been sufficiently studied. We performed stochastic simulations to compare instrumental insemination strategies and mating on IMS in terms of genetic progress and inbreeding development. We focused on the role of paternal generation intervals, which can be shortened to two years with instrumental insemination in comparison to three years when using IMS. After 70 years, instrumental insemination yielded up to 42% higher genetic gain than IMS strategies-particularly with few available mating sites. Inbreeding rates with instrumental insemination and IMS were comparable. When the paternal generation interval in instrumental insemination was stretched to three years, the number of drone producers required for sustainable breeding was reduced substantially. In contrast, when shortening the interval to two years, it yielded the highest generational inbreeding rates (up to 2.28%). Overall, instrumental insemination with drones from a single colony appears as a viable strategy for honeybee breeding and a promising alternative to IMS.

Long-Term Evaluation of Breeding Scheme Alternatives for Endangered Honeybee Subspecies.

Modern breeding structures are emerging for European honeybee populations. However, while genetic evaluations of honeybees are becoming increasingly well understood, little is known about how selection decisions shape the populations' genetic structures. We performed simulations evaluating 100 different selection schemes, defined by selection rates for dams and sires, in populations of 200, 500, or 1000 colonies per year and considering four different quantitative traits, reflecting different genetic parameters and numbers of influential loci. Focusing on sustainability, we evaluated genetic progress over 100 years and related it to inbreeding developments. While all populations allowed for sustainable breeding with generational inbreeding rates below 1% per generation, optimal selection rates differed and sustainable selection was harder to achieve in smaller populations and for stronger negative correlations of maternal and direct effects in the selection trait. In small populations, a third or a fourth of all candidate queens should be selected as dams, whereas this number declined to a sixth for larger population sizes. Furthermore, our simulations indicated that, particularly in small populations, as many sires as possible should be provided. We conclude that carefully applied breeding provides good prospects for currently endangered honeybee subspecies, since sustainable genetic progress improves their attractiveness to beekeepers.

Conservation priorities of genetic diversity in domesticated metapopulations: a study in taurine cattle breeds.

We estimated neutral diversity of 21 European cattle breeds with 105 microsatellites. Nine of them resembled unselected Balkan Busa strains with diffuse breeding barriers and the 12 others were strongly differentiated, isolated breeds. Because of the impact of neutral genetic diversity on long-term population adaptive capacity, we discuss the long-term outcome of different conservation priorities in a subdivided metapopulation of the investigated cattle breeds. The optimal contribution to a pool of total genetic diversity allocated more than 95% of long-term relevant neutral diversity to virtually unselected strains of the Balkan Busa, while the maximization of total variance preferred inbred breeds. Current artificial selection methods, such as genomic selection sped up and a recovery of underestimated traits becomes quickly impossible. We emphasize that currently neutral and even deleterious alleles might be required for future genotypes in sustainable and efficient livestock breeding and production systems of a 21st century. We provide cumulative evidences that long-term survival relies on genetic complexity and complexity relies on allelic diversity. Our results suggest that virtually unselected, nonuniform strains harbor a crucial proportion of neutral diversity and should be conserved with high global priority. As one example, we suggest a cooperative maintenance of the nondifferentiated, highly fragmented, and fast vanishing metapopulation of Balkan Busa.