Development of wheat—Hordeum chilense Chromosome 2Hch Introgression Lines Potentially Useful for Improving Grain Quality Traits

The chromosome 2Hch of Hordeum chilense. has the potential to improve seed carotenoid content in wheat as it carries a set of endosperm carotenoid-related genes. We have obtained structural changes in chromosome 2Hch in a common wheat (Triticum aestivum L. “Chinese Spring”) background by crossing a wheat double disomic substitution 2Hch(2D) and 7Hch(7D) line with a disomic addition line carrying chromosome 2Cc from Aegilops cylindrica Host.. Seven introgressions of chromosome 2Hch into wheat were characterized by fluorescence in situ hybridization (FISH) and DNA markers. Chromosome-specific simple sequence repeats (SSRs) were used for identifying wheat chromosomes. In addition, we tested 82 conserved orthologous set (COS) markers for homoeologous group 2, of which 65 amplified targets in H. chilense and 26 showed polymorphism between H. chilense and wheat. A total of 24 markers were assigned to chromosome 2Hch with eight allocated to 2HchS and 16 to 2HchL. Among the seven introgressions there was a disomic substitution line 2Hch(2D), a ditelosomic addition line for the 2HchL arm, an isochromosome for the 2HchL arm, a homozygous centromeric 2HchS·2DL translocation, a double monosomic 2HchS·2DL plus 7HchS·D translocation, a homozygous centromeric 7HchS·2HchL translocation and, finally, a 2HchL·7HchL translocation. Wheat—H. chilense macrosyntenic comparisons using COS markers revealed that H. chilense chromosome 2Hch exhibits synteny to wheat homoeologous group 2 chromosomes, and the COS markers assigned to this chromosome will facilitate alien gene introgression into wheat. The genetic stocks developed here include new wheat—H. chilense recombinations which are useful for studying the effect of chromosome 2Hch on grain quality traits.

Lutein esterification in wheat endosperm is controlled by the homoeologous group 7, and is increased by the simultaneous presence of chromosomes 7D and 7Hch from Hordeum chilense

The high carotenoid content in tritordeum (×Tritordeum Ascherson et Graebner) grains is derived from its wild parent, Hordeum chilense Roem. et Schulz. Phytoene synthase 1 (Psy1) is located on chromosome 7HchS and plays a major role in this trait. This study investigates the impact of the introgression of chromosome 7Hch into common wheat background on carotenoid composition, including xanthophylls esterified with fatty acids (monoesters and diesters). All of the genetic stocks carrying Psy1 from H. chilense increased their carotenoid content relative to common wheat. In addition, significant changes in the carotenoid profile were detected in different genetic stocks. The most relevant was the increase in content of lutein diesters when both 7Hch and 7D were present, which indicates the existence of genes involved in the esterification of xanthophylls in both chromosomes. Furthermore, our results suggest that 7Hch genes preferentially esterify lutein with palmitic acid, whereas 7D is either indifferent to the fatty acid or it prefers linoleic acid for lutein esterification. The involvement and complementarity of 7Hch and 7D are highly significant considering the scarcity of previous results on lutein esterification in wheat.

Isolation and characterization of a wheat – Psathyrostachys huashanica ‘Keng’ 3Ns disomic addition line with resistance to stripe rust

We isolated a wheat germplasm line, 22-2, which was derived from common wheat (Triticum aestivum ‘7182’) and Psathyrostachys huashanica ‘Keng’ (2n = 2x = 14, NsNs). Genomic composition and homoeologous relationships of 22-2 was analyzed using cytology, genomic in situ hybridization (GISH), EST–SSR, and EST–STS to characterize the alien chromatin in the transfer line. The cytological investigations showed that the chromosome number and configuration were 2n = 44 = 22 II. Mitotic and meiotic GISH using P. huashanica genomic DNA as the probe indicated that 22-2 contained a pair of P. huashanica chromosomes. The genomic affinities of the introduced P. huashanica chromosomes were determined by EST–SSR and EST–STS using multiple-loci markers from seven wheat homoeologous groups between the parents and addition line. One EST–SSR and 17 EST–STS markers, which were located on the homoeologous group 3 chromosomes of wheat, amplified polymorphic bands in 22-2 that were unique to P. huashanica. Thus, these markers suggested that the introduced Ns chromosome pair belonged to homoeologous group 3, so we designated 22-2 as a 3Ns disomic addition line. Based on disease reaction to mixed races (CYR31, CYR32, and Shuiyuan14) of stripe rust in the adult stages, 22-2 was found to have high resistance to stripe rust, which was possibly derived from its P. huashanica parent. Consequently, the new disomic addition line 22-2 could be a valuable donor source for wheat improvement depending on the excellent agronomic traits, especially, the introduction of novel disease resistance genes into wheat during breeding programs.