Genetic analysis of gas-exchange based on high throughput estimates of transpiration and stomatal conductance in maize (Zea mays L.)

SANTIAGO ALVAREZ PRADO; LLORENÇ CABRERA-BOSQUET; AUDE COUPEL-LEDRU; ANTONIN GRAU; CLAUDE WELCKER; FRANÇOIS TARDIEU

Hyderabad

Conferencia; InterDrought - V; 2017

ICRISAT

Plants tend to decrease transpiration underwater deficit and/or high evaporative demand by closing stomata and reducingleaf growth. Identification of sources of genetic variability for underlying mechanismsis necessary to design genotypes adapted to stressing climatic scenarios. Aseries of four experiments was performed in the PhenoArch image-based phenotypingplatform (M3P, France) with contrasting soil water status and evaporativedemand. We used a diversity panel of 255 maize hybrids genotyped with 832K polymorphic SNPs. Equivalent stomatalconductance at plant level was estimated in the studied 1680 x 4 plants byinversion of the Penman Monteith equation. It changed with light intensity andvapor pressure deficit, with different thresholds and slopes between genotypes.Maximum values ranged from 52 to 76 mmol m-2 sec-1 dependingon hybrids. The sensitivity of leaf expansion to soil water potential wascalculated over the four experiments as the slope of the relationship of leafexpansion rate to soil water potential. For each hybrid, a common linearrelationship applied to the four experiments. The x-intercepts of theserelationships, which indicate the driest soil in which a plant still has anappreciable leaf growth, ranged from -0.6 to -1.6 MPa depending on hybrids. AGWAS analysis was performed on all variables presented above, suggestinginteresting candidate genes related to hydraulics and other mechanisms. Surprisingly,no co-location was observed between QTLs of stomatal conductance and ofsensitivity to soil water deficit, supporting the idea that the controls ofstomatal opening/photosynthesis and of leaf expansion are largely independent.