Phytoene synthase 1 (Psy-1) and lipoxygenase 1 (Lpx-1) genes influence on semolina yellowness in wheat Mediterranean germplasm

Phytoene synthase-1 and Lipoxygenase-1 genes regulate for the increased synthesis and decreased catalysis of carotenoid pigments in durum wheat, respectively, resulting in pasta yellow color. A wheat RIL population derived from a cross between genotypes with contrasting yellow index (YI) was tested in Italy during three seasons and the parental lines were evaluated for Lpx relative expression. The Lpx-4B candidate gene was mapped into a QTL region, and eight QTL for YI were mapped on chromosomes 2B (one), 4A (one), 4B (three), 5A (two) and 7A (one). Psy1-A1 gene co-localized in a major QTL on chromosome 7A. A panel comprising 128 ancient and modern Mediterranean durum wheat genotypes was tested for semolina yellowness (b*values) in three Chilean environments and characterized for genes related to carotenoid synthesis and degradation. Out of 11 allelic groups (five Lpx-B1 haplotypes with three Psy1-A1 alleles), groups 3, 5 modern and 8 exhibited the highest semolina yellowness (b*values > 19.0). qPCR showed that a high yellowness landrace, which peaked at 42 days post anthesis, had up to 7.5 times higher Psy-1 expression than a low yellowness landrace, showing the important role of Psy1 in determining semolina yellowness during grain filling.