Control of expansive growth in water deficit: from phenotyping to field simulations

BORIS PARENT; LLORENÇ CABRERA-BOSQUET; MARIA ANGELA CANÉ; FRANÇOIS CHAUMONT; SANTIAGO ALVAREZ PRADO; CECILIO FROIS CALDEIRA JUNIOR; SÉBASTIEN LACUBE; DELPHINE FLEURY; CLAUDE WELCKER; ROBERTO TUBEROSA; FRANÇOIS TARDIEU

Montpellier

Conferencia; Recent progress in drought tolerance: from genetics to modelling; 2015

Maintenance of expansive growth under water deficit has been selected as a key target trait of DROPS because of its early response in drying conditions, its large genetic variability, its partially common control with reproductive growth and its consequences on light interception and transpiration.Development of methods to measure shoot growth in Phenotyping platforms (PhenoArch and Phenodyn, M3P, Montpellier, France; The Plant Accelerator, Adelaide, Australia) allowed identification of a large genetic variability in maize, wheat and durum wheat. Three-D characterization of individual plant architecture and of the spatial distribution of light in phenotyping platforms allowed calculation of light interception and of Radiation Use Efficiency (RUE) of hundreds of genotypes. Measurements of leaf elongation rate with a temporal definition of a few minutes allowed comparison of time courses of growth and of physiological variables that are candidate for the control of expansive growth. Overall, these methods resulted in progress in physiological understanding and in dozens of QTLs identified for shoot growth in bread wheat and maize, peduncle in durum wheat, RUE, transpiration and phenology in all three species.The importance of hydraulics in the control of leaf expansion rate (LER) has been demonstrated. Changes in LER occurred over a few minutes upon changes in evaporative demand and soil water status. LER also varied with circadian-driven changes in plant hydraulic conductance in continuous light. Rapid changes of LER with water deficit and evaporative demand are due to stomatal movements and changes in hydraulic conductivity related to aquaporin Plasma Membrane Intrinsic Proteins (PIPs). Both PIP expression and plant hydraulic conductance rapidly changed with environmental conditions and with the circadian clock. In addition to its value, this result was essential to establish a protocol for comparing transcript amounts of PIPs in genotypes of the maize panel (eQTLs). A large genetic variability has been observed for the progression of shoot development (phyllochron), for whole-plant leaf growth and for their responses to water deficit. Accurate QTLs have been identified for each of these variables, which are compared with the positions of QTLs of PIP transcript amounts, and of accumulation of abscisic acid and of metabolites in the leaf. This will results in new insights on the control of growth under water deficit.The position of QTLs of growth in response to drought has been compared to the positions of QTLs of yield in the field in the three species. In addition, the effects of introgressed genomic regions have been analyzed on the growth of several organs (leaf, peduncle, roots) and on yield of durum wheat and maize. The analysis of impact on yield of growth QTLs is based on colocation of QTLs between platforms and fields, and on a model for scaling up the effects of growth in the field. We have designed for that a model of shoot development that takes into account the responses of individual leaves to water deficit and evaporative demand, with parameters that are measured in a phenotyping platform for all genotypes of the panels. The model is incorporated into the crop model APSIM-maize, for estimation of the effect of QTLs of leaf growth on crop yield in hundreds of climatic scenarios, current or future.