Physiological-genetic dissection of drought resistance in wild emmer wheat

Wild emmer wheat (Triticum turgidum ssp. dicoccoides (Korn.) Thell.), the allo-tetraploid (BBAA) progenitor of cultivated wheats, offers a valuable source of allelic diversity for various economically important traits, including drought resistance. A total of 160 wild emmer accessions, consisting of 25 populations, and three control durum wheat cultivars were examined under two irrigation regimes, well-watered control (~650 mm) and water-limited (~250 mm). Principal component analysis, supported by photosynthetic rate measurements, revealed a variety of drought adaptive strategies among the wild accessions. A wide phenotypic variation was found both between and within the wild emmer populations in most morpho-physiological traits, with a considerable advantage in drought resistance over cultivated genotypes. Microsatellite markers revealed a wide allelic diversity between and within the wild emmer populations, confirming the patterns of phenotypic variation. The greatest drought resistance capacity corresponded with the highest allelic diversity and found in populations from intermediate aridity level. Physiological responses to drought were further dissected by quantitative trait loci (QTLs) mapping of yield and drought related traits under contrasting irrigation regimes, using 152 F6 recombinant inbred lines derived from a cross between durum wheat and wild emmer wheat from drought-prone environment. A total of 102 QTLs were mapped for 10 productivity and morpho-physiological traits. Several QTLs exhibited GxE interaction and accounted for productivity and related physiological traits under either the well watered or water-limited conditions. The identified genetic resources and QTLs detected, shed new light on drought adaptive complexes in wheat and expected to facilitate the improvement of drought resistance in elite wheat cultivars.