<i>Psy-E1</i> derived from <i>Thinopyrum ponticum</i> contributes strong yellowness to durum wheat but may cause yield loss in Japan

Strong yellow color, caused by carotenoid accumulation, in semolina flour made from durum wheat (<i>Triticum turgidum</i> L. subsp. <i>durum</i> (Desf.)) is one of the most important traits for pasta production. The first step in the carotenoid biosynthesis pathway, which is catalyzed by phytoene synthase (PSY), is a bottleneck, and allelic variation of <i>Psy-A1</i> in durum wheat produces different yellow pigment contents (YPC) in seeds. Durum wheat carrying leaf rust resistance gene <i>Lr19</i>, which was translocated from wheat relative <i>Thinopyrum ponticum</i> chromosome 7E to durum wheat chromosome 7A, is known to produce high YPC, and the causal gene is presumed to be <i>Psy-E1</i>, which is tightly linked to <i>Lr19</i>. In this study, <i>Psy-E1</i> produced higher YPC than <i>Psy-A1</i> alleles, such as <i>Psy-A1k</i>, <i>Psy-A1l</i> and <i>Psy-A1o</i>, in durum wheat. Segregation analysis demonstrated that <i>Psy-E1</i> is located at the <i>Psy-A1</i> locus on chromosome 7A. In a 2-year field test of near-isogenic materials, <i>Psy-E1</i> was accompanied by yield loss with decreases in grain number per spike, test weight and thousand-kernel weight under moisture conditions typical of wheat-growing areas of Japan. Thus, <i>Psy-E1</i> has the potential to contribute high YPC in durum wheat breeding programs, although the applicable cultivation environments are limited.