QTL Mapping of Wood FT-IR Chemotypes Shows Promise for Improving Biofuel Potential in Short Rotation Coppice Willow (Salix spp.)

Abstract

An increasing interest to convert lignocellulosic biomass into biofuels has highlighted the potential of using willows for this purpose, due to its fast growth in short rotation coppice systems. Here, we use a mapping population of 463 individuals of a cross between Salix viminalis and S. viminalis × S. schwerinii to investigate the genetic background of different wood chemical traits, information of importance for breeding towards different uses of wood. Furthermore, using a subset of the mapping population, the correlation between biogas production and chemical traits was investigated. The phenotyping of wood was carried by Furriertransformed-Infrared spectrometry (FT-IR) and water content analysis. Quantitative trait loci (QTLs) analysis was used to identify regions in the genome of importance for the phenotypic variation of these chemical traits. We found 27 QTLs for various traits. On linkage group (LG) VI-1, QTLs for signals assigned to G-lignin, lignin, and the S/G ratio were collocated and on LG XIV we found a cluster of QTLs representing signals assigned to lignin, cellulose, hemicellulose, and water. The QTLs explained from 3.4 to 6.9% of the phenotypic variation indicating a quantitative genetic background where many genes influence the traits. For the biogas production, a positive and negative correlation was seen with the signals assigned to acetyl and lignin, respectively. This study represents a first step in the understanding of the genetic background of wood chemical traits for willows, information needed for complementary studies, mapping of important genes, and for breeding of varieties for biofuel production purposes.

Biomass Recalcitrance in Willow Under Two Biological Conversion Paradigms: Enzymatic Hydrolysis and Anaerobic Digestion

“…BMP values for the material in this study averaged 198.0 Nml CH 4 /g biomass, with the highest BMP samples yielding almost 250 Nml CH 4 /g. A similar maximum value, albeit with a slightly lower mean of 149.7 Nml CH 4 /g VS, was found by Pawar et al [38], using non-pretreated Salix milled to the approximate particle size of the present study and using continuous stirring during incubation. Slightly higher values (mean 250, maximum 320 Nml CH 4 /g VS) were found in a study evaluating several Salix and Populus species [37].…”

“…Positive correlations between S/G ratio and AD performance in degradation of lignocellulosic materials have generally been reported, for example, in Populus biomass using C. thermocellum [45], in AD of herbaceous material [46], as well as in the present study. However, in a study on non-pretreated Salix, evaluating correlations between methane potentials and rates and FT-IR spectral features [38], some G lignin-assigned wavenumbers were positively correlated with both potentials and rates, although this finding was confounded by positive correlations between these wavenumbers and carbohydrate content. Taken together, the results may point to a difference in the effect of S/ G ratio on deconstruction of non-pretreated material that is dependent on the origin of the cellulolytic enzymes (fungal vs. bacterial).…”

Lignin Engineering in Forest Trees

“…Indeed, large variation in lignin amount and S/G composition already exists in natural populations of forest trees (Studer et al, 2011). Given that both traits affect the glucose release upon saccharification (Yoo et al, 2018), exploiting this genetic diversity by conventional breeding, aided by Genome Wide Association Studies (GWAS) (Porth et al, 2013; Fahrenkrog et al, 2017; Liu et al, 2018), Breeding with Rare Defective Alleles (BRDA) (Vanholme et al, 2013a) or genomic selection (Yin et al, 2010; Muchero et al, 2015; Pawar et al, 2018; Xie et al, 2018), is a valuable strategy to obtain lines that have improved wood processing efficiency. Once elite trees are obtained by these breeding methods, genetic engineering and CRISPR-based gene editing of specific genes is a very promising avenue to further improve these elite genotypes without breaking up their genetic constitution and without going through lengthy breeding cycles.…”

Evaluation of Wood Quality Traits in Salix viminalis Useful for Biofuels: Characterization and Method Development

“…Recent developments in society for changing from a fossil-based to a circular bioeconomy has created greater interest for using short-rotation coppice plants (e.g., willow) as a potential biomass source for transport biofuels such as bioethanol and biogas [1][2][3][4][5][6][7]. The use of bioenergy is ever increasing having grown by 150% since 2000 in the EU, while the use of biofuels in transport is up 25-fold; thus, there is a great surge after biomass raw materials of which coppice plants are expected to provide an important part [8].…”