Root Rot Resistance Locus PaLAR3 Is Delivered by Somatic Embryogenesis (SE) Pipeline in Norway Spruce (Picea abies (L.) Karst.)

Jaanika Edesi,Ulrika Egertsdotter,Malin Elfstrand,Åke Olson,Mikko Tikkinen,Saila Varis,Tuija Aronen

doi:10.3390/f12020193

Jaanika Edesi, Ulrika Egertsdotter + Show 5 more

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https://doi.org/10.3390/f12020193

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Abstract

Research Highlights: The Norway spruce somatic embryogenesis (SE) pipeline is suitable for multiplication of material with root rot resistance traits. Background and Objectives: Heterobasidion root rot is the economically most severe forest pathogen in Europe, reducing the benefit of planting elite forest material. In this study, the SE-propagation ability of elite Norway spruce material carrying root rot resistance traits was studied. Materials and Methods: We analyzed the presence of the root rot resistance locus PaLAR3B among 80 Finnish progeny-tested Norway spruce plus-trees used for SE-plant production as well as in 241 SE lines (genotypes) derived from them. Seven full-sib families with lines having either AA, AB, or BB genotype for PaLAR3 locus were further studied for their SE-plant propagation ability. Results: The results indicate that 47.5% of the studied elite trees carry the PaLAR3B allele (45% are heterozygous and 2.5% homozygous). The resistance allele was present among the SE lines as expected based on Mendelian segregation and did not interfere with somatic embryo production capacity. All embryos from PaLAR3 genotypes germinated well and emblings were viable in the end of first growing season. However, in three families, PaLAR3B homo- or heterozygotes had 23.2% to 32.1% lower viability compared to their respective hetero- or PaLAR3A homozygotes. Conclusions: There is no trade-off between root rot resistance locus PaLAR3B and somatic embryo production ability, but the allele may interfere with Norway spruce embling establishment.

Highlights

Norway spruce (Picea abies (L.) Karst.) is one of the most important conifers in Europe, providing valuable raw material for forest industries [1]
As the resistance allele PaLAR3B is associated with higher (+)-catechin accumulation in Norway spruce, the aim of the present study was to analyze whether the presence of this allele, PaLAR3B, interferes with somatic embryogenesis (SE)-plant production
The results indicate that 47.5% of the 80 Finnish plus-trees used for SE-initiations carry the PaLAR3B allele (45% are heterozygous and 2.5% homozygous) (Table 1)

Summary

Introduction

Norway spruce (Picea abies (L.) Karst.) is one of the most important conifers in Europe, providing valuable raw material for forest industries [1]. The stem and root rot caused by members of the Heterobasidion annosum s.l. species complex is considered the most severe fungal forest disease occurring in Norway spruce in Europe. H. annosum s.l. incidence has been projected to increase in the future, threatening the expected productivity increase associated with planting elite forest regeneration materials [2,3]. The Norway spruce genome harbors genetic variability in root rot resistance which could be utilized in breeding for more resistant forest regeneration material [4]. Detected 13 quantitative trait locus (QTL) regions in the Norway spruce genome controlling resistance to Heterobasidion parviporum. Variation in one gene, leucoanthocyanidin reductase 3 (PaLAR3) comprising one of the QTLs, is known to a play role in root rot resistance [6]

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