Inheritance studies of caffeine and theobromine content of Mate (Ilex paraguariensis) in Misiones, Argentina

In order to start a genetic improvement program for quality in the Mate crop (Ilex paraguariensis), it was attempted to estimate the actual genetic parameters of caffeine, theobromine and related quality traits, using available progeny tests in Misiones, Argentina. Using cluster analysis, eight groups of similar characteristics could be identified, and individual within full-sib family selection for quality was performed. Additive effects were strong for caffeine but weak for theobromine. Co-heritability between caffeine and theobromine was positive, suggesting that additive genetic correlations and dominance correlations are concurring. The strong influence of paternal progenitors regarding caffeine needs more research. This revised version was published online in August 2006 with corrections to the Cover Date.     

Benefits and complications of maximum likelihood estimation in (composite) interval mapping methods using EM and ECM

Normal mixtures are applied in interval mapping to model the segregation of genotypes following Mendel's Law in successive generations of crossing. Standard methods use least squares or maximum likelihood estimates. Theoretically, maximum likelihood is known to result in more efficient estimates than least squares. In the interval mapping literature, some authors state that both methods yield equivalent results, whereas other authors emphasize the higher efficiency of maximum likelihood. The present paper investigates differences of both methods more closely. We show by example the occurrence of multiple LOD-Score profiles when applying maximum likelihood estimation methods for a basic interval mapping and composite interval mapping model. This analysis results in some peaks of the LOD-Score profile that distinctly differ from F-statistic profiles without being spurious. A spurious profile for IM and CIM was found as well. It is concluded that users of IM and CIM mapping software must be prepared for the rare occurrence of spurious solutions in LOD profiles. The example indicates that especially in sparse marker maps maximum likelihood estimation has a potential to result in non-spurious profiles that are not similar to the F-statistic profiles. However, the discrimination of spurious and non-spurious further profiles is not straightforward in applications. Until the mathematical background of this phenomenon is investigated more thoroughly and rules to ascertain the information content of these additional solutions have been developed, the simultaneous use of the least squares and ML methods may caution against the rare occurrence of spurious results. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inbreeding and fertility in Irish Wolfhounds in Sweden: 1976 to 2007

Background

Given that no influence of inbreeding on life expectancy could be demonstrated in Irish Wolfhounds in a previous study, it was decided to test the influence of inbreeding and other parameters on fertility in this breed.

Methods

The study was based on all Irish Wolfhound litters registered in Sweden between 1976 and 2007 (n = 822 litters) as provided by the Swedish Kennel Club (SKK) and combined with a pedigree database going back to 1862. Analyses were performed using linear regression in a Generalised Linear Model and other tests in the SAS system^®.

Results

Mean number of pups per litter was 6.01 ± 2.65, with a maximum of 13. There were no significant differences in either the number of litters or the number of pups between years of birth. Males were used for breeding at a significantly earlier age than females. Mean number of litters per parent was 2.96 ± 3.14 for males and 1.59 ± 0.87 for females. No influence of Wright''s inbreeding coefficients over 5, 10, 20 and 30 generations and/or Meuwissen''s inbreeding coefficients on litter size was detected. In the Generalised Linear Model, highly significant, but weak (coefficient of determination (R²) = 0.0341) influences were found for maternal age at mating as well as maternal inbreeding measured by Wright''s inbreeding coefficient over 30 generations and Meuwissen''s inbreeding coefficient. Paternal inbreeding coefficients over 5, 10, 20 and 30 generations and calculated after Meuwissen, as well as maternal inbreeding coefficients over 5, 10 and 20 generations did not have significant effects on litter size.

Conclusion

The low coefficient of determination (R²) value of the Generalised Linear Model indicates that inbreeding does not have a strong influence on fertility in Irish Wolfhounds, which is consistent with earlier results and the breed''s genetic history. These results likely reflect the aforementioned genetic history and should not be extrapolated to other breeds without prior breed-specific research.     

Lifespan and disease predispositions in the Irish Wolfhound: a review

Several disease predispositions of Irish Wolfhounds are mentioned in the veterinary literature, but these lists vary greatly between different publications. This article reviews findings on lifespan as well as disease predispositions that have been reported in the literature. Hereditary mechanisms found so far are discussed, including their implications for breeding healthier dogs, the ethical necessity of which is stressed under the aspect of animal welfare. An open health registry, combined with the estimation of breeding values, seems to be the most promising approach. Furthermore, routine male castration is discouraged as being associated with an increased osteosarcoma risk. Mean lifespan estimates in Irish Wolfhounds vary between 4.95 and 8.75 years, but bias due to right censored data is common. The diseases reported to occur most frequently are dilated cardiomyopathy, osteogenic sarcoma, gastric dilation and volvulus and diseases of the osteochondrosis spectrum. Furthermore, intrahepatic portosystemic shunt plays an important role. Several other diseases have been reported in the literature, including rhinitis, epilepsy, progressive retinal atrophy, von Willebrand's Disease, and juvenile fibrocartilaginous embolism.