Toward improved drought tolerance in bioenergy crops: <scp>QTL</scp> for carbon isotope composition and stomatal conductance in <i><scp>P</scp>opulus</i>

Abstract

Abstract Dedicated non‐food bioenergy crops like poplar are needed as sustainable, low‐input feedstocks for renewable energy in a future drier climate, where they can be grown on marginal soils. Such plants should have a low water, carbon, and chemical footprint. Capturing natural variation in traits associated with water use efficiency ( WUE ) is the first step to developing trees that require less water and may be adapted to drier environments. We have assessed stomatal conductance ( g s ) and leaf carbon isotope composition (δ 13 C, an indirect indicator of leaf WUE ) in two P opulus species, P . deltoides and P. trichocarpa and their F 2 progeny, grown in the United Kingdom and in I taly. P opulus deltoides leaves showed lower δ 13 C than P. trichocarpa , suggesting a higher WUE in P . trichocarpa , although without drought preconditioning, g s of P. trichocarpa was less responsive to dehydration and abscisic acid treatment than P . deltoides , suggesting that leaf anatomy may also contribute to δ 13 C in P opulus . Quantitative trait loci ( QTL ) were identified for δ 13 C on eight linkage groups ( LG ) and two QTL for g s . From these. QTL and differential gene expression in response to drought from microarray data, we focused on three hotspots and identified 23 novel candidate genes on LG VI , X, and XVI . We have begun to unravel the genetic basis of WUE in bioenergy P opulus revealing important underpinning data for breeding and improvement in poplar genotypes for a future drier climate.