Abstract
BackgroundConcern over land use for non-food bioenergy crops requires breeding programmes that focus on producing biomass on the minimum amount of land that is economically-viable. To achieve this, the maximum potential yield per hectare is a key target for improvement. For long lived tree species, such as poplar, this requires an understanding of the traits that contribute to biomass production and their genetic control. An important aspect of this for long lived plants is an understanding of genetic interactions at different developmental stages, i.e. how genes or genetic regions impact on yield over time.ResultsQTL mapping identified regions of genetic control for biomass yield. We mapped consistent QTL across multiple coppice cycles and identified five robust QTL hotspots on linkage groups III, IV, X, XIV and XIX, calling these 'Poplar Biomass Loci' (PBL 1–5). In total 20% of the variation in final harvest biomass yield was explained by mapped QTL. We also investigated the genetic correlations between yield related traits to identify 'early diagnostic' indicators of yield showing that early biomass was a reasonable predictor of coppice yield and that leaf size, cell number and stem and sylleptic branch number were also valuable traits.ConclusionThese findings provide insight into the genetic control of biomass production and correlation to 'early diagnostic' traits determining yield in poplar SRC for bioenergy. QTL hotspots serve as useful targets for directed breeding for improved biomass productivity that may also be relevant across additional poplar hybrids.
Highlights
Concern over land use for non-food bioenergy crops requires breeding programmes that focus on producing biomass on the minimum amount of land that is economicallyviable
Biomass accumulation in the first and subsequent years remained a reasonable predictor of biomass yield through to Coppice Cycle 2 (CC2)-4 (Biomass 1), suggesting that early screening for elite genotypes would be a reliable indicator of sustained productivity
In general we mapped Quantitative Trait Loci (QTL) explaining a relatively large % percentage variance explained (Vp) for numerous traits associated with biomass yield (Figures 3 and 4, Table 2 and Additional file 2 see [6] for an in-depth multivariate analysis of Single Stem (SS) and Coppice Cycle 1 (CC1) data), typically with few QTL explaining the largest percentage of trait variation (Additional file 1)
Summary
Concern over land use for non-food bioenergy crops requires breeding programmes that focus on producing biomass on the minimum amount of land that is economicallyviable. For long lived tree species, such as poplar, this requires an understanding of the traits that contribute to biomass production and their genetic control. There is currently a new wave of interest in the use of biomass as a renewable fuel source, both for heat and electricity production as well as for liquid transport fuels such as bioethanol, from biochemical fermentation or bio-oil from thermo-chemical conversion. This is true for second generation lignocellulosic crops that are unlikely to compete with food crops on agricultural land. To date, breeding efforts and scientific studies have concentrated on single-stem growth of poplars and there is a need to identify traits and genomic loci as targets for the development of improved SRC biomass-yielding genotypes
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