Combining genetic resources and elite material populations to improve the accuracy of genomic prediction in apple.

Genomic selection is an attractive strategy for apple breeding that could reduce the length of breeding cycles. A possible limitation to the practical implementation of this approach lies in the creation of a training set large and diverse enough to ensure accurate predictions. In this study, we investigated the potential of combining two available populations, i.e., genetic resources and elite material, in order to obtain a large training set with a high genetic diversity. We compared the predictive ability of genomic predictions within-population, across-population or when combining both populations, and tested a model accounting for population-specific marker effects in this last case. The obtained predictive abilities were moderate to high according to the studied trait and small increases in predictive ability could be obtained for some traits when the two populations were combined into a unique training set. We also investigated the potential of such a training set to predict hybrids resulting from crosses between the two populations, with a focus on the method to design the training set and the best proportion of each population to optimize predictions. The measured predictive abilities were very similar for all the proportions, except for the extreme cases where only one of the two populations was used in the training set, in which case predictive abilities could be lower than when using both populations. Using an optimization algorithm to choose the genotypes in the training set also led to higher predictive abilities than when the genotypes were chosen at random. Our results provide guidelines to initiate breeding programs that use genomic selection when the implementation of the training set is a limitation.

Fear of falling and associated activity restriction in older people. results of a cross-sectional study conducted in a Belgian town.

OBJECTIVES: This article aims at describing, in a Belgian town, the frequency of the fear of falling and of subsequent activity restriction among non-institutionalised people aged 65 years and over, and at identifying persons affected by these two issues. METHODS: Cross-sectional survey conducted in Fontaine l'Evêque (Belgium) in 2006, using a self-administered questionnaire. RESULTS: The participants could fill in the questionnaire on their own or with the help of a third party if needed. The latter were not taken into account in this article. Analyses covered 419 questionnaires. Fear of falling and activity restriction were reported by, respectively, 59.1% and 33.2% of participants. They were more frequent among fallers but also affected non-fallers. In logistic regression analyses: gender, the fact of living alone and the number of falls were significantly associated with fear of falling; gender, age and the number of falls were significantly associated with activity restriction. CONCLUSIONS: Our study, despite various limitations, shows the importance of fear of falling and of subsequent activity restriction among older people, among fallers as well as among non-fallers. It also provides information, though limited, concerning persons affected by these two issues in Belgium, and in other contexts as well. Given the ageing of our populations, it is important to take these problems into account when caring for older people.