Jean Dufour

Rising Out of the Ashes: Additive Genetic Variation for Crown and Collar Resistance to Hymenoscyphus fraxineus in Fraxinus excelsior

Since the early 1990s, ash dieback due to the invasive ascomycete Hymenoscyphus fraxineus is threatening Fraxinus excelsior in most of its natural range. Previous studies reported significant levels of genetic variability in susceptibility in F. excelsior either in field or inoculation experiments. The present study was based on a field experiment planted in 1995, 15 years before onset of the disease. Crown and collar status were monitored on 777 trees from 23 open-pollinated progenies originating from three French provenances. Health status was modeled using a Bayesian approach where spatiotemporal effects were explicitly taken into account. Moderate narrow-sense heritability was found for crown dieback (h2 = 0.42). This study is first to show that resistance at the collar level is also heritable (h2 = 0.49 for collar lesions prevalence and h2 = 0.42 for their severity) and that there is significant genetic correlation (r = 0.40) between the severities of crown and collar symptoms. There was no evidence for differences between provenances. Family effects were detected, but computing individual breeding values showed that most of the genetic variation lies within families. In agreement with previous reports, early flushing correlates with healthier crown. Implications of these results in disease management and breeding are discussed.

Wild Cherry Breeding (Prunus avium L.)

Wild cherry (Prunus avium L.) is native from central-eastern European temperate forests and it has only recently been introduced in intensive forest tree farming practices outside its natural range. Characterised by allogamy with pollination provided by honey bees, it is also able to spread by root stumps in juvenile phases of the ecosystem.

La sélection participative en France : des plantes annuelles aux ligneux

Breeding good varieties of uncommon forest species may be achieved through a lengthy, expensive conventional breeding programme. For some annual plants and tropical forest species, participatory breeding or domestication achieves good results and better dissemination of the varieties. This approach was initiated in France taking the wild cherry tree as a model, for which there are many existing schemes and cultivars that can be used as controls to evaluate the varieties and select new individuals while fine-tuning the methodology. The model can be applied to other species: we show that the wild cherry tree controls may be used for other species when soil and climate requirements are similar. Highly intensive breeding in nurseries would rapidly enable seed orchards to be set up