J. Ballesteros

Tritordeum: Triticale’s New Brother Cereal

The amphiploids between Hordeum chilense and Triticutn spp. (tritordeum) resemble their wheat parents agronomically. We have synthesized more than one hundred primary tritordeums for breeding a new cereal crop. From the results obtained on the first two cycles of selection, in which the yield level of tritordeum was raised to that of traditional wheat varieties, it is clear that tritordeum has the potential to become a crop when sufficient breeding effort is applied. Tritordeum is already been exploited as a bridge for introducing the genetic variability available in the section Anisolepis of the genus Hordeum into wheat.

Field evaluation and agronomic performance of transgenic wheat.

Abstract.Seven transgenic lines of wheat have been evaluated under field conditions during 2 agonomic years. Four lines contained the transgenes for β-glucuronidase (uidA), herbicide resistance (bar) and for one high-molecular-weight (HMW) subunit, and three lines contained only one transgene for one HMW glutenin subunit and no marker genes. Agronomic traits and yield components were studied in transgenic lines and compared with the non-transgenic parent and null segregant lines. Although phenotypic differences for many traits have been found, only heading date and the number of spikelets per spike showed clear genotypic differences for both field trials. All transgenic lines had a longer heading date than parent lines whereas the number of spikelets per spike in transgenic lines was around that for L88-31 and higher for L88-6 than the corresponding parent lines. No differences were found between lines constitutively expressing the uidA and bar genes from those which only expressed the HMW genes. We conclude that differences between transgenic lines and their parents are small, and could be eliminated by backcrossing transgenic lines with their parents and selecting for the wanted genotype.

Functional properties of flours from field grown transgenic wheat lines expressing the HMW glutenin subunit 1Ax1 and 1Dx5 genes

The high molecular weight glutenin subunits (HMW-GS) of wheat are major determinants of the viscoelastic properties of gluten and dough. The bread making quality of field grown transgenic lines of bread wheat expressing the HMW-GS 1Ax1 or 1Dx5 genes were evaluated over a two year period. Subunit 1Ax1 represented about 29% and 48% of the total HMW-GS in lines 1-2 and 2-2, respectively, while subunit 1Dx5 represented 65.4% and 62% of the total HMW-GS in transgenic lines 6-2 and 9, respectively. The expression of subunits 1Ax1 or 1Dx5 in transgenic wheat led to corresponding decreases in the proportions of endogenous HMW-GS. HMW-GS 1Ax1 and 1Dx5 had contrasting effects on dough quality determined by the Alveograph and sedimentation test. Subunit 1Ax1 increased the tenacity (P), extensibility (L), deformation work (W), and sedimentation value, with the increase being related to the level of expression. In contrast, subunit 1Dx5 led to a smaller increment in the tenacity (P), but to drastic decrease in both extensibility (L), deformation work (W), and the sedimentation value. Expression of subunit 1Ax1 in transgenic wheat resulted in lines with improved rheological properties whereas the lines expressing subunit 1Dx5 resulted in unsuitable breadmaking-related characteristics.

The reaction of x Tritordeum and its Triticum spp. and Hordeum chilense parents to rust diseases

SummaryHexaploid and octoploid tritordeums and their parents Hordeum chilense and Triticum spp. were screened for resistance to isolates of wheat and barley yellow and brown rusts. All H. chilense lines were highly resistant to both wheat and barley brown rust, few lines were susceptible to wheat yellow rust while susceptibility to barley yellow rust was common. In general the resistance of tritordeum is predominantly contributed by the wheat parent and apparently the genes for resistance in H. chilense are inhibited in their expression by the presence of the wheat genome.

Development and cytogenetic characterisation of a double goat grass-barley chromosome substitution in tritordeum

Abstract×Tritordeum (Ascherson et Graebner, an amphiploid between Triticum turgidum conv. durum and Hordeum chilense), and chromosome substitution lines of tritordeum where chromosomes 2 Hch or 3 HchH. chilense were replaced with chromosome 2 D of T. aestivum or 3 Hv chromosome of H. vulgare, respectively, were used to assess the effect of specific chromosomes on the rachis. ×Tritordeum has brittle rachis while the 2 D(2 Hch) and 3 Hv (3 Hch) substitution lines have non-brittle rachis. Both lines also have compact spikes, a character highly desirable for the improvement of tritordeum threshability. Different combinations of 2 D and 3 Hv translocations were developed in tritordeum. In this article we present information on the identification and characterisation of all these introgression lines by the fluorescent in situ hybridisation.

Introgression of 1Dx5+1Dy10 into tritordeum.

Abstract.The uses of hexaploid tritordeum as a crop for human consumption require improvement of its bread-making quality. For this purpose chromosome 1D of bread wheat with the Glu-D1 allele encoding for high-molecular-weight glutenin subunits Dx5+Dy10 was introgressed into tritordeum. Different primary tritordeums were crossed with wheats carrying subunits Dx5+Dy10. The hybrids were backcrossed to tritordeum and seeds for the next backcross (or selfing) were selected for the presence of chromosome 1D using SDS-PAGE. Forty two chromosome plants carrying subunits Dx5+Dy10 were obtained after two backcrosses and selfing. Chromosome characterization of these plants using fluorescence in situ hybridisation (FISH) proved that either chromosome substitution 1Hch/1D or 1A/1D had been obtained. A homozygous plant with a translocation of the entire 1DL arm to 1HchS was also obtained. The complete chromosome substitution lines have better agronomic characteristics than the lines with translocations.