High resolution mapping of traits related to whole-plant transpiration under increasing evaporative demand in wheat.

Rémy Schoppach,Walid Sadok,Ute Baumann,Elisabeth Majerus,Elodie Claverie,Delphine Fleury,Radoslaw Suchecki,Julian D Taylor

doi:10.1093/jxb/erw125

Abstract

Atmospheric vapor pressure deficit (VPD) is a key component of drought and has a strong influence on yields. Whole-plant transpiration rate (TR) response to increasing VPD has been linked to drought tolerance in wheat, but because of its challenging phenotyping, its genetic basis remains unexplored. Further, the genetic control of other key traits linked to daytime TR such as leaf area, stomata densities and - more recently - nocturnal transpiration remains unknown. Considering the presence of wheat phenology genes that can interfere with drought tolerance, the aim of this investigation was to identify at an enhanced resolution the genetic basis of the above traits while investigating the effects of phenology genes Ppd-D1 and Ppd-B1 Virtually all traits were highly heritable (heritabilities from 0.61 to 0.91) and a total of mostly trait-specific 68 QTL were detected. Six QTL were identified for TR response to VPD, with one QTL (QSLP.ucl-5A) individually explaining 25.4% of the genetic variance. This QTL harbored several genes previously reported to be involved in ABA signaling, interaction with DREB2A and root hydraulics. Surprisingly, nocturnal TR and stomata densities on both leaf sides were characterized by highly specific and robust QTL. In addition, negative correlations were found between TR and leaf area suggesting trade-offs between these traits. Further, Ppd-D1 had strong but opposite effects on these traits, suggesting an involvement in this trade-off. Overall, these findings revealed novel genetic resources while suggesting a more direct role of phenology genes in enhancing wheat drought tolerance.

Highlights

Drought is the major factor limiting yield production in wheat (Tester and Langridge, 2010)
Considering the presence of wheat phenology genes that can interfere with drought tolerance, the aim of this investigation was to identify at an enhanced resolution the genetic basis of the above traits while investigating the effects of phenology genes Ppd-D1 and Ppd-B1
Lobell et al (2014) reported that atmospheric vapor pressure deficit (VPD) has a much stronger effect on current and future yields than previously thought. This effect poses a major challenge for a crop such as wheat whose worldwide yield stagnation has been associated with an increase in the frequency of heat and drought events (e.g. Brisson et al, 2010), both resulting in high-VPD conditions

Summary

Introduction

Drought is the major factor limiting yield production in wheat (Tester and Langridge, 2010). One often-overlooked variable in quantifying drought impact on yield is air vapor pressure deficit (VPD) This variable, which is termed ‘atmospheric drought’, encapsulates the combined effects of air temperature (T) and relative humidity (RH), and is the main driving force of the whole-plant transpiration rate (TR) (Monteith, 1995). In natural environments, both T and RH contribute to the variation in VPD: on a sunny day, VPD typically increases as T increases and RH decreases progressively throughout the day. This effect poses a major challenge for a crop such as wheat whose worldwide yield stagnation has been associated with an increase in the frequency of heat and drought events (e.g. Brisson et al, 2010), both resulting in high-VPD conditions

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