Breeding for Boundaries: using specific and general quantitative disease resistance to control compartmentalization of necrotrophic stem decay pathogens in breeding

This study aims to contribute new understanding of quantitative disease resistance (QDR) in Norway spruce (spruce) to support resistance breeding in Sweden. QDR is the dominating form of resistance in plants yet understanding of QDR is insufficient.

The result from this proposal is likely to challenge, and change, the current paradigm on forest tree resistance to stem decay pathogens, which suggests that it is broad-spectrum QDR (resistance to multiple pathogens). Yet recent work suggest that spruce QDR can be specific to either H. parviporum or H. annosum s.s.

We will investigate genetic variation and cellular responses in three spruce QDR trait loci (QTL) likely involved in QDR to stem pathogens.

We will test the hypotheses:The B-QTLs PaLAC5 and FAX2-like will confer higher resistance to several species of pathogens i.e. confer broad-spectrum QDRSpecific alleles at the S-QTL matairesinol synthase will confer resistance only to specific isolates or species of pathogens i.e conferring species-specific QDRAllelic variation in PaLAC5, FAX2 (B-QTLs) and matairesinol synthase (S-QTL) is involved in compartmentalization of pathogens in the stem.Allelic variation in FAX2-like and matairesinol synthase loci generate different profiles of fatty acids or lignans respectively.In southern Sweden the losses can reach well above 20% of the harvested trees for Heterobasidion decay alone.

Identification and use of trees with robust B-QDR is an opportunity to reduce the losses.