Productivity, leaf traits and carbon isotope discrimination in 29 Populus deltoides × P. nigra clones

Abstract

Summary• Here we tested whether some leaf traits could be used as predictors for productivity in a range of Populus deltoides × P. nigra clones. These traits were assessed in 3-yr-old rooted cuttings from 29 clones growing in an open field trial, in a five randomized complete block design, under optimal irrigation.• Variables were assigned to four groups describing productivity (above-ground biomass, total leaf area), leaf growth (total number of leaves increment rate), leaf structure (area of the largest leaf, specific leaf area, carbon and nitrogen contents), and carbon isotope discrimination in the leaves ( ∆ ).• High-yielding clones displayed larger total leaf area and individual leaf area, while no correlation could be detected between productivity and either leaf structure or ∆ . By contrast, ∆ was negatively correlated with number of leaves increment rate and leaf N content.• Our study shows that there is a potential to improve water-use efficiency in poplar without necessarily reducing the overall productivity. IntroductionPoplars are among the fastest growing trees under temperate latitudes. Their large productivity is associated with large water requirements and, as a consequence, a tight dependency of productivity upon water availability (Ceulemans et al ., 1988;Tschaplinski & Blake, 1989;Barigah et al ., 1994;Tschaplinski et al ., 1994;Zsuffa et al ., 1996). To sustain the extension of poplar cultivation from flood plains and bottomlands towards uplands where soil water availability is subjected to seasonal changes, more water-use efficient hybrids are required. One functional trait that could be of interest as an index for improved or maintained productivity under reduced water availability is the intrinsic water-use efficiency (Wi), i.e. the ratio between net CO 2 assimilation and stomatal conductance. Wi can be indirectly estimated at leaf level, via the carbon isotope discrimination ( ∆ ), assuming the occurrence of a linear and negative correlation between ∆ and intrinsic water-use efficiency shown both for cereals (Farquhar & Richards, 1984;Farquhar et al ., 1989) and for trees (Ponton et al ., 2001). This trait is easily measurable, highly heritable and has been used as a selection criterion in crop breeding Rebetzke et al ., 2002). Among tree species, it also displays a high heritability (Brendel et al ., 2002) and a large variability at interspecific level (Guehl et al ., 1998;Bonal et al ., 2000;Ponton et al ., 2001) and provenance level (Lauteri et al ., 1997;Roupsard et al ., 1998) as well as at family level (Brendel et al ., 2002). Such a clonal diversity of ∆ has already been shown to occur among poplars (Zhang et al ., 2004;Marron et al ., 2005). The detection of clones combining satisfactory productivity and high

Variation génétique de la productivité, de caractères foliaires et de la discrimination isotopique vis-à-vis du carbone chez des hybrides de peuplier cultivés sur des sites contrastés

“…Such genetic variability had already been observed from younger plant material in previous studies in hybrid poplars growing in a glasshouse or in the field (Al Afas et al, 2007;Ceulemans and Deraedt, 1999;Marron et al, 2005;Monclus et al, 2005;Voltas et al, 2006).…”

“…The links between productivity and Δ differ according to poplar species: a positive relationship was found for Populus davidiana (Dode) Schneider (Zhang et al, 2004), whereas none was detected for Populus trichocarpa × P. deltoides (TD hybrids) and Populus deltoides × P. nigra (DN hybrids) Monclus et al, 2005;Rae et al, 2004). The lack of correlation observed for these two hybrids suggests the possibility to select genotypes displaying simultaneously a high productivity and water-use efficiency.…”

“…While Δ l is an integrative indicator of intrinsic water-use efficiency at a leaf life time-scale (Farquhar and Richards, 1984) and in nursery in 2003 (black triangles) (Monclus et al, 2005) and 2004 (White triangles) (Monclus et al, 2006). Glasshouse and nursery measurements had been recorded from plants grown under well-watered condition.…”

“…A detailed study with several commercial poplar genotypes (DN hybrids) grown as young cuttings in glasshouse (3-month-old rooted cuttings; Marron et al, 2005) or in a nursery (1 to 4-year-old rooted cuttings coppiced each year; Monclus et al, 2005; indicated consistent genotypic differences in W i , and a lack of correlation between W i and productivity. The stability of these observations remains to be established under a wider range of environmental conditions and with older trees, as some juvenility effects might interfere with the observed ranking.…”

Genotypic variation in transpiration of coppiced poplar during the third rotation of a short‐rotation bio‐energy culture

“…However, the occurrence of a significant genotypic variability for productivity and for Δ 13 C (used as a proxy of WUE) in poplars and other tree species has been demonstrated, including a negative relationship between biomass and Δ 13 C (Cassasoli et al., 2004; Guehl, Nguyen‐Queyrens, Loustau, & Ferhi, 1994; Monclus et al., 2009; Zhang, Zang, & Li, 2004) or an opposite pattern (Marron et al., 2005; Rae, Robinson, Street, & Taylor, 2004). WUE in poplars is highly heritable (Monclus et al., 2005, 2006) and there is generally no trade‐off between WUE and productivity. Thus, the relationship between productivity and WUE seems to be a function of the genetic background and probably of the parentage, although further studies are needed to identify the genomic determinants of productivity and WUE via a QTL (Quantitative Trait Loci) approach.…”