Portrait photo of Maria Rosario Garcia-Gil Photo: Juha Niemi

Norway spruce and Scots pine are the two most economically important species in Fennoscandia. Despite several decades of breeding activity both species remain mostly undomesticated and thus still retain great potential for improvement. The traditional phenotype-based selection of superior trees is now undergoing a fast revolution where genomic-based selection (Genomic Selection) can substitute costly field tests. 

Genomic selection full potential requires of accurate and high-throughput phenotyping tools which will allow incorporating into the breeding programs a number of properties which otherwise were too expensive or tedious to measure, such as wood physical and chemical properties.

Genomic Selection (GS) for wood properties

Genomic prediction using genome-wide dense markers or genomic selection (GS) was first introduced by Theo Meuwissen. The method builds on the estimation of the effect of large numbers of DNA markers covering the entire genome and subsequently predict the genomic value of individuals that have been genotyped, but not phenotyped. As compared to the phenotypic mass selection based on a pedigree-based relationship matrix (A matrix), genomic prediction relies on constructing a marker-based relationship matrix (G matrix). The superiority of the G-matrix is the result of a more precise estimation of genetic similarity based on Mendelian segregation that not only captures recently pedigree but also the historical pedigree, and corrects possible errors in the pedigree. At MRGG´s lab we develop GS models for wood physical (density, MFA, MOE…) and chemical (cellulose, hemicellulose, lignin…) properties in Norway spruce. Aspects such as phenotyping efficient protocols for wood properties, single nucleotide polymorphisms (SNP) coding, environmental factors, progeny size, consanguinity are part of the model development for its implementation into operational breeding.

Collage of four graphs with a bundel of lowering black lines overlayed by one red line. Radial trends for MFA of Picea abies at two trials (Höreda and Erikstorp) from cambial age 1 to 20 and for Pinus contorta at two trials (Övra and Lagfors) from cambial age 1 to 30. The black lines represent the actual observations from all individual trees and the red line is the mean radial variation of MFA against the cambial age.

Inbreeding depression in Scots pine

In Sweden, conifer breeders are aware about the possible negative effect of increased inbreeding, so called inbreeding depression (ID), after successive cycles of selection. Moreover, inbreeding has been suggested, although not empirically evaluated, as a potential breeding tool through the exploitation of within-species heterosis. With no doubt inbreeding management is a central question in conifer breeding that has mostly been address through theoretical models, whereas empirical data has not been generated to probe any of those models right. At MRGG´s lab we conduct genomic studies on inbreed crosses of Scots pine to dissect the genetic control of inbreeding and its potential exploitation in conifer breeding.

Collage of five graphs showing the ring on the x-axis in relation to ring width (top left), stem diameter (top right), wood density (bottem left), microfibril angle (MFA; bottom middle) and modulus of elasticity (MOE; bottom right)Mean values generated with SilviScan data from the open-pollinated progenies and from the clonal archive.

Local adaptation in response to light quality

As a consequence of climate change, it is expected mean temperature to increase in 1.5 oC to 2oC, which is seen by the breeders as an opportunity for assisted migration northwards of the southern genotypes to benefit from their genetically governed extended growth. This would result in a substantial gain in volume. However, in addition to potential limitations in the extention of the growth season such as early spring frost, there are certain environmental cues that are not expected to change following the climate change, but to which trees are also adapted, such as light quality, day length and light intensity. This could limit the value of assisted migration. At MRGG´s lab we are investigating the genetic basis of local adaptation to light intensity and quality. During the growth season the trees in the north are exposed to higher proportions of far-red (FR) to red (R) light, which has resulted in a steep local adaptation to the response to R/FR ratio. These studies have involved greenhouse, cabinet experiments in combination with microarray and transcriptomic (RNAseq) data.

Shade avoidance response in conifers

Plants sense and respond to light quality and intensity, which is reflected at all different stages of seedling development. Response to shade differs among species in both angiosperms and gymnosperms depending on their level of tolerance to shade. Shade avoidance syndrome (SAS) is well-characterized in the shade intolerant model species A. thaliana whereas much less is known about the shade tolerance response (STR). At MRGG´s we conduct comparative studies in two conifer species with contrasting responses to shade; Scots pine, (shade-intolerant) and Norway spruce (shade-tolerant), with the aim to understand mechanisms behind SAS and STR in conifers.  

Key Publications

  • Ranade SS & García-Gil MR (2013). Adaptive cline to light spectra in Scots pine (Pinus sylvestris L). Tree physiology. 4: 479-493
  • Ranade SS, Abrahamsson S, Niemi J, and García-Gil MR (2013). Comparison of global expression profile under red light and far- red light in a conifer species. American Journal of Plant Science 4:479-493
  • Abrahamsson S, Hallander J, Waldmann P and García-Gil MR (2013). Heterozygosity-fitness correlation (HFC) in an inbreed Scots pine population. Genetica, DOI10.1007/s10709-013-9704-y
  • Nystedt B et al (2013). The draft sequence of the 20 GBp Norway spruce (Picea abies) genome (shed light on conifer genome evolution). Nature doi:10.1038/nature12211
  • Sillanpää MJ, Pikkuhookana P, Abrahamsson S, Fries A and García-Gil MR (2012). Simultaneous estimation of multiple quantitative trait loci and growth curve parameters through hierarchical Bayesian modeling. Heredity 108(2): 134-146
  • Abrahamsson S, Nilsson JE, Wu H, García-Gil MR, Andersson B (2012). Inheritance of height growth and autumn cold hardiness based on two generations of full-sib and half-sib families of Pinus sylvestris. Scandinavian Journal of Forest Research. 27:415-413