Phenotyping strategies to enhance peanut drought tolerance and molecular markers for crop improvement Jyostna M. Devi, T.R. Sinclair, V.Vadez, A. Shekoofa, N. Puppala
Mura, J. D.  2017.  In Genomics Assisted Breeding of Crops for Abiotic Stress Tolerance, Volume 2, Springer.  (in press)

The production of peanut (Arachis hypogaea L.) in warm environments and on sandy soils makes the crop vulnerable to soil drying to some extent in nearly every cropping season. Several traits are being explored to overcome some of the yield decrease that results 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 explanations 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 a water-conservation phenotype that can result in yield increase, 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 combining physiological and field-based investigations that allowed identification of tolerant genotypes with potential yield increase in water-limited environments. Genetic markers development in peanut lags behind other crop species due to low levels of molecular polymorphism and its complex polyploidy genome. However, recent progress in molecular genetic technology has made it possible to measure polymorphism in peanut and to identify molecular marker or Quatitative trait loci (QTLs).