urum wheat (DW), Triticum turgidum L. ssp. durum (Desf.) Husn., genome BBAA, is a cereal grain mainly used for pasta production and evolved from domesticated emmer wheat (DEW), T. turgidum ssp. dicoccum (Schrank ex Schübl.) Thell. DEW itself derived from wild emmer wheat (WEW), T. turgidum ssp. dicoccoides (Körn. ex Asch. & Graebn.

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The yellow colour of durum wheat (Triticum turgidum L. var durum) semolina is due in part to the presence of carotenoid pigments found in the endosperm and is an important end-use quality trait. We hypothesized that variation in the genes coding for phytoene synthase (Psy), a critical enzyme in carotenoid biosynthesis, may partially explain the phenotypic variation in endosperm colour observed among durum cultivars. Using rice sequence information, primers were designed to PCR clone and sequence the Psy genes from Kofa (high colour) and W9262-260D3 (medium colour) durum cultivars. Sequencing confirmed the presence of four Psy genes in each parent, corresponding to a two member gene family designated as Psy1-1, Psy1-2 and Psy2-1 and Psy2-2. A genetic map was constructed using 155 F1-derived doubled haploid lines from the cross W9262-260D3/Kofa with 194 simple sequence repeat and DArT markers. Using Psy1-1 and Psy2-1 allele-specific markers and chromosome mapping, the Psy1 and Psy2 genes were located to the group 7 and 5 chromosomes, respectively. Four quantitative trait loci (QTL) underlying phenotypic variation in endosperm colour were identified on chromosomes 2A, 4B, 6B, and 7B. The Psy1-1 locus co-segregated with the 7B QTL, demonstrating an association of this gene with phenotypic variation for endosperm colour. This work is the first report of mapping Psy genes and supports the role of Psy1-1 in elevated levels of endosperm colour in durum wheat. This gene is a target for the further development of a molecular marker to enhance selection for endosperm colour in durum wheat breeding programs.

Quantification of the drought tolerance of wheat (Triticum spp.) genotypes is of interest to physiologists investigating traits associated with adaptation to dry conditions and to breeders developing cultivars for dry areas. The objective of this research was to assess drought tolerance in terms of minimal depression of yield in dry compared with favorable environments (drought susceptibility index, S) with a superiority measure (P) based on the sum across environments of the mean‐squared differences between genotype yield and the maximum yield in each environment. Twenty‐five hexaploid (T. aestivum L.) and 16 tetraploid (T. turgidum L. var. durum) wheat genotypes were grown in separate experiments under dry and irrigated conditions on a Swinton loam (Aridic Haploboroll) soil. There was year‐to‐year variation in S within genotypes and changes in genotype ranking within years. No single cause for this variability was identified. The S index did not differentiate between potentially drought‐tolerant genotypes and those that had low yield potential from other causes. P was correlated with mean yield in both the hexaploid (−0.96**) and tetraploid (−0.94**) groups (both significant at P = 0.01). However, P was strongly influenced by high yield environments; this was alleviated by standardization of the yield data. Although P appears to be a possible method to quantify average superiority of genotypes across locations, its suitability requires further assessment. There seems to be no simple technique to quantify drought tolerance that would assist physiologists in choosing genotypes in which to evaluate putative drought tolerance mechanisms.