The diversity of 13C isotope discrimination in a Quercus robur full-sib family is associated with differences in intrinsic water use efficiency, transpiration efficiency, and stomatal conductance

Abstract

(13)C discrimination in organic matter with respect to atmospheric CO(2) (Delta(13)C) is under tight genetic control in many plant species, including the pedunculate oak (Quercus robur L.) full-sib progeny used in this study. Delta(13)C is expected to reflect intrinsic water use efficiency, but this assumption requires confirmation due to potential interferences with mesophyll conductance to CO(2), or post-photosynthetic discrimination. In order to dissect the observed Delta(13)C variability in this progeny, six genotypes that have previously been found to display extreme phenotypic values of Delta(13)C [either very high ('high Delta') or low ('low Delta') phenotype] were selected, and transpiration efficiency (TE; accumulated biomass/transpired water), net CO(2) assimilation rate (A), stomatal conductance for water vapour (g(s)), and intrinsic water use efficiency (W(i)=A/g(s)) were compared with Delta(13)C in bulk leaf matter, wood, and cellulose in wood. As expected, 'high Delta' displayed higher values of Delta(13)C not only in bulk leaf matter, but also in wood and cellulose. This confirmed the stability of the genotypic differences in Delta(13)C recorded earlier. 'High Delta' also displayed lower TE, lower W(i), and higher g(s). A small difference was detected in photosynthetic capacity but none in mesophyll conductance to CO(2). 'High Delta' and 'low Delta' displayed very similar leaf anatomy, except for higher stomatal density in 'high Delta'. Finally, diurnal courses of leaf gas exchange revealed a higher g(s) in 'high Delta' in the morning than in the afternoon when the difference decreased. The gene ERECTA, involved in the control of water use efficiency, leaf differentiation, and stomatal density, displayed higher expression levels in 'low Delta'. In this progeny, the variability of Delta(13)C correlated closely with that of W(i) and TE. Genetic differences of Delta(13)C and W(i) can be ascribed to differences in stomatal conductance and stomatal density but not in photosynthetic capacity.

Is the ranking of poplar genotypes for leaf carbon isotope discrimination stable across sites and years in two different full-sib families?

“…The occurrence of a negative and linear relationship between Δ and W i was confirmed among others in poplars (Monclus et al 2006), in oaks (Roussel et al 2009) and in a range of tropical trees (Cernusak et al 2007), although it has been stated that the relation might differ among species (Warren and Adams 2006;Seibt et al 2008). It is often assumed that a low Δ (or large W i ) comes at the expense of growth, i.e.…”

The genetics of water-use efficiency and its relation to growth in maritime pine

“…Rather, more research is needed to support the interest of the Corsican genetic background in hybrid combination with the Landes provenance, which is well adapted to the Aquitaine region, especially in terms of frost resistance. To gain more insights into the functional background of observed variability in WUE, an approach of choosing specific genotypes for detailed studies, as has been done for pedonculate oak (Brendel et al , 2008; Roussel et al ., 2009a, b), might be feasible. The genetic material created within the maritime pine breeding programme (recurrent selection scheme between the Landes and Corsican genepools in the early 1980s and large progeny provenance tests of Corsican ecotypes in the 2010s) provide further research grounds to study the genetics of WUE in this species.…”

A linkage disequilibrium perspective on the genetic mosaic of speciation in two hybridizing Mediterranean white oaks

“…In particular, genes and/or QTL responsible for divergent ecological adaptations have been mapped and characterized (Saintagne et al, 2004;Porth et al, 2005: Parelle et al, 2007Brendel et al, 2008;Roussel et al, 2009;Le Provost et al, 2011), reproductive isolation barriers have been analyzed in detail (Gailing et al, 2005;Abadie et al, 2012;Lepais et al, 2013) and long-range haplotypic LD, a mechanism capable of physically linking both types of genes, seems to be the rule around putatively selected loci (Goicoechea et al, 2012). These are the three basic requirements for ecological speciation (Rundle and Nosil, 2005;Nosil, 2012), although other speciation types may also be possible for these oaks.…”