Genetic variability of growth maintenance under drought: from phenotyping platforms to the field

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Tardieu, Francois, F. | Welcker, Claude

Edité par CCSD -

International audience. Expansive growth of leaves or of reproductive organs such as silks are affected by water deficit before any reduction in photosynthesis or root growth. An approach combining quantitative genetic, physiology and ecophysiological modelling has been developed to disentangle the genetic basis of growth response to soil water deficit and evaporative demand. - The analysis of a mapping population in 7 fields in Mexico, Kenya and India suggests that the genetic determinisms of leaf area and of grain yield are in good part common, with an overall correlation between both variables. - A considerable genetic variability was observed for the sensitivities of leaf growth to water deficit and evaporative demand, measured in phenotyping platforms. In populations of RILs or in panels of unrelated lines, some lines had their growth stopped at a soil water potential of –0.6 MPa while other continued growing until –1.6 MPa. There is therefore a considerable natural genetic variability which can be exploited for breeding. A limited number of genomic regions were repeatedly associated with the sensitivity to soil water deficit and evaporative demand across mapping populations. - The dynamic nature of responses of leaf growth to changes in soil water status or evaporative demand suggests that hydraulic processes significantly contribute to genetic differences in growth maintenance in maize and rice. In particular, abscisic acid largely contributes to increase the tissue hydraulic conductivity, whole plant hydraulic conductance and growth recovery via an increase in aquaporin content and activity. Turgor and hydraulic conductivity play an important role in changes in leaf growth rate. - Comparative mapping in a tropical maize mapping population shows that the genetic determinism of leaf growth maintenance under water deficit is partly common with that of the maintenance of reproductive development1. This suggests common mechanisms between source and sink strengths, with profound consequences for designing drought tolerant ideotypes. - Common QTLs for leaf growth were observed in phenotyping platforms and in the field. Both modelling and experiment show that QTLs for organ growth translate into differences in yield5, opening route to new approaches of breeding combining MAS and modelling

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