Genetics of Hordeum chilense– Current Status

Hordeum chilense, a South-American wild barley, is being used in cereal breeding because of its good crossability with both wild and cultivated Triticeae species. Amphiploids and chromosome addition lines of H. chilense in common and durum wheats have been obtained as a means to transfer desirable agronomic characters from wild barley to wheat. No allosyndetic pairing has been detected in diverse hybrids involving H. chilense. Several biochemical markers have been associated with the seven chilense chromosome pairs. New approaches are necessary to transfer genes from H. chilense to cereals.     

Reaction of tritordeum to Fusarium culmorum and Septoria nodorum

Summary Hordeum chilense is a wild barley extensively used in wide crosses in the Triticeae. It could be a valuable source of resistance to Fusarium culmorum and Septoria nodorum. Some H. chilense x Triticum spp. amphiploids, named tritordeums, were more resistant than the parental wheat line to these diseases, others were not. Average contents of ergosterol and deoxynivalenol (DON) suggested that resistance to colonization by Fusarium was the highest for Hordeum chilense, followed by tritordeum and wheat in decreasing order. In particular, the H. chilense genotypes H7 and H17 enhanced the wheat resistance to F. culmorum in its tritordeum offsprings. Resistance to S. nodorum in tritordeum was not associated with tall plant height. There is sufficient genetic variation for resistance to F. culmorum and S. nodorum among tritordeum to allow the breeding of lines combining short straw and resistance to both diseases.     

Chromosomal localization of genes for carotenoid pigments using addition lines of Hordeum chilense in wheat

×Tritordeum sp. (Ascherson et Graebner) is the amphiploid obtained after chromosome doubling of hybrids between Hordeum chilense (Roem. et Schult.) and diploid, tetraploid or hexaploid wheats. Tritordeums have consistently higher carotenoid pigment contents than durum or bread wheat. Two distinct H. chilense accessions (used for the synthesis of tritordeum) were analysed for this trait. The chromosomal localization of the genes coding the ability of H. chilense to increase the carotene content of wheat were carried out using two sets of wheat- H. chilense addition lines. The a arm of chromosome 7H^ch is proposed to be responsible for the high carotene content in tritordeum. The implication of this finding in wheat breeding is discussed.     

The Rheological Properties and Baking Performances of Flours from Hexaploid Tritordeums

Hexaploid tritordeum (XTritordeumAscherson et Graebner) is the amphiploid obtained from the cross between a South American wild barley (Hordeum chilenseRoem. et Schulz.) and durum wheat (Triticum turgidumconv.durumDesf. em. M.K.). The bread making characteristics of eight lines of hexaploid tritordeum have been analysed, together with those of one bread wheat cultivar. The results indicated that, in general, the tritordeums yielded flours with quality properties similar to those of bread wheat, although their rheological and baking characteristics were slightly poorer. Despite the small number of samples, a range of variation was shown for some quality characters. This intra-specific variability suggests that, using well-established breeding procedures, it may be feasible to produce better quality tritordeums.     

The Amphiploid Hordeum chilense× Triticum aestivum ssp. sphacrocoecum. Variability in Octoploid Tritordeum

In order to increase variability in the octopioid tritordeum a new octoploid tritordeum has been synthesized after colchicine doubling of the chromosomes of the Hordeum chilense × Triticum aestivum ssp. sphaerococcum hybrid. The amphiploid showed full pairing in 30 % of the pollen mother cells, The fertility was higher than in previous tritordeums (1.65 grains per spikelet and 43.00 grains per spike). Hybrids between the octoploid tritorceums were sterile. However, hexaploid × octopiold trhordeum hybrids were fertile and secondary tritordeums were extracted with increased fertility.     

Hordeum chilense resistance to powdery mildew and its potential use in cereal breeding

Summary Hordeum chilense is a wild barley with high crossability with Triticum, Hordeum and Secale. Its amphiploid with wheat, tritordeum, has potential as a new crop. H. chilense is highly resistant to the powdery mildew diseases of both wheat and barley. Whereas tritordeum is resistant to barley powdery mildew, its reaction to wheat powdery mildew is similar to that of its wheat parent. However H. chilense contributes to a reduced density of mildew colonies. This quantitative resistance of tritordeum is diluted at higher ploidy levels.     

Analysis of D-prolamins synthesized by the Hordeum chilense genome and their effects on gluten strength in hexaploid tritordeum

Hexaploid tritordeum is the amphiploid derived from the cross between Hordeum chilense and durum wheat. The storage proteins synthesized in the H^ch genome influence the gluten strength of this amphiploid. The D‐prolamins of H. chilense have been analysed by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis with and without urea. A new locus named Glu‐H^ch3 has been detected. The effects of allelic variation at this locus on gluten strength, as measured the sodium dodecyl sulphate sedimentation test, were determined using seeds of 92 lines from a cross of two hexaploid tritordeum lines. Two allelic variants have been detected for this locus, which have shown different effects on gluten strength.     

Chromosomal location of genes for carotenoid pigments in Hordeum chilense

In wheat, carotenoids are very important for end‐use quality in noodle production. Hexaploid tritordeums are the amphiploids derived from the cross between a wild diploid barley (Hordeum chilense) and durum wheat. Hexaploid tritordeums exhibit a higher carotenoid content than their respective wheat parents. The cross between H1 and H7 lines of H. chilense was used in order to map quantitative trait loci (QTL) for carotenoid content. Multiple interval mapping identified one QTL mapped on chromosome 2. This knowledge is helpful to transfer this favourable trait to other cereal genomes because of the high crossability of H. chilense with other members of the tribe Triticeae.