Fortsättningsansökan – studera förutsättningarna för att förbättra askens genetiska motståndskraft mot askskottsjukan

Bakgrund

Från Föreningen Skogsträdsförädling erhöll Lars-Göran Stener, Skogforsk, totalt 122 000 kr för år 2011 till inventering, analys och rapportskrivning om olika kloners resistens mot askskottsjukan i fröplantagerna i Snogeholm och Trolleholm.

Genomförande

1. Inventering av de enskilda trädens vitalitet, skador avseende askskottsjukan samt av vår- och höstfenologi i askfröplantagerna i Snogeholm och Trolleholm under år 2011.
2. Statistiska analyser och rapportskrivning.
3. En vetenskaplig artikel är inlämnad för revision till Scandinavian Journal of Forest Research.

Resultatet kan sammanfattas enligt följande

Ash dieback damages was assessed and analysed on 16 – 22 year-old grafts in two ash seed orchards (). The grafts originated from 106 plus-tree clones selected from 27 stands in southern Sweden based on their phenotypes.

The results obtained indicate that ash dieback disease is strongly genotypically controlled. There was considerable genotypic variation among individuals. None of the clones seemed to be totally resistant, bur some exhibited reduced susceptibility and retained this resistance after six years under heavy infection pressure. Together with the high heritability of resistance, strong age x age correlations and weak genotype x environment interactions, this suggests there is good scope for breeding less susceptible trees for the future.

The first objective of the hypothetical breeding plan should be to enlarge the population of less susceptible individuals as a matter of urgency. The results suggest that such “healthy” trees in natural ash stands are quite rare, implying that it will be necessary to gather a large number of candidates for breeding in order to achieve useful results from the selection process. Collecting scions from healthy trees in damaged stands all over the distribution area of ash is probably a cost-effective way of selecting candidates. However, such activities will have to be performed quite soon, before all of the trees in severely damaged ash stands are harvested.

The result presented are very promising and suggest that future breeding programs have the potential to produce healthy ash stands.