Résumé
The production of peanut (Arachis hypogaea L.) in warm environments and on sandy soils makes the crop vulnerable to soil drying in nearly every cropping season. Several traits are being explored to overcome yield decreases resulting from the inevitable water deficits that develop in the soil. In this review, two traits: (1) an early limitation on transpiration rate (TR) as the soil dries, and (2) limitation on maximum TR (TRlim) under high vapor pressure deficit (VPD) in peanut will be discussed. Both of these traits result in water conservation by limiting plant transpiration rates and are potential reasons for genetic variation in Transpiration Efficiency (TE). The basis for transpiration response to soil water deficits and high VPD at the tissue and whole plant levels appears to be leaf and root hydraulic properties. A contributing factor in determining hydraulic limitations is water Transport through membranes via aquaporins (AQP). Overall, both of the two traits result in phenotypes with an ability to conserve water especially under late-season drought events. While large genetic variability in these traits has been observed in peanut, breeding efforts are still required to exploit these promising traits in commercial cultivars. This review focuses on the traits in peanut that allow identification of tolerant genotypes with potential yield increase in water-limited environments. A recent progress in molecular marker technology has made it possible to measure polymorphism in peanut and to identify molecular markers or quantitative trait loci (QTL) linked to TE and its surrogate traits despite its low levels of molecular polymorphism and complex polyploid genome. We also reviewed some of these QTLs and their potential application for molecular breeding in peanut under water-limited environments.