Wheat chromosome engineering at the 4x level: the potential of different alien gene transfers into durum wheat

Abstract

With the aim of making the point on feasibility and relative success of alien transfers into durum wheat via chromosome engineering, three transfer works, differing in origin and content of the alien introduction and in the transfer strategy adopted, are described. For the transfer of a powdery mildew resistance gene, Pm13, originating from Aegilops longissima and previously transferred to common wheat chromosome 3B, as well as for that of the leaf rust resistance gene Lr19 and its associated Yp (yellow pigment) gene, deriving from Ag. elongatum and introduced into 7A, the common wheat recombinants were employed as donors, from which the alien segments were homologously transferred into durum genotypes. On the other hand, for the transfer of common wheat chromosome 1D seed storage protein genes, phl mediated homoeologous recombination was repeatedly induced. This resulted in loss of individuals, including potentially desirable recombinants, probably due to imbalances created by thephl condition. However, recovered Gli-DllGlu-D3 tetraploid recombinants exhibited normal transmission and fertility. Preliminary evidence indicates a normal behaviour also for Glu-D1 '5 + 10' putative recombinants. Similarly, there was no negative impact from the transfer of the Pm13 gene, which has been successfully pyramided into Pm4a durum varieties. On the contrary, transfer of the Ag. elongatum segment showed normal female but almost no male transmission in one durum genotype. This in spite of the fact that the alien segment, proved to be, through in situ hybridization, considerably longer than previously believed, should contain an Sd-1 gene, causing preferential transmission in common wheat. While its behaviour is being checked in other durum genotypes, shortening of the alien segment, throughphl induced recombination, is also being carried out. Possible causes of the severe negative selection that this alien transfer seemingly encounters at the tetraploid level are discussed.

Chromosome composition of an F2 Triticum aestivum×T. turgidum spp. durum cross analysed by DArT markers and MCFISH

“…Hexaploid bread wheats (T. aestivum L.), with the chromosome constitution AABBDD (2n=6x=42), provide an excellent resource for the genetic enhancement of durum, due to the shared AABB tetraploid chromosome compliment and the potential for transfer of desirable D genome loci into durum. For example, the gluten quality of durum wheat has been significantly improved by the introgression of D genome segments (Ceoloni et al 1996;Pogna and Mazza 1996).…”

Transfer and Molecular Mapping of Aegilops Tauschii-Derived Hessian Fly Resistance Genes (H22, H23, H24, and H26) From D Genome of Triticum Aestivum Onto a Genome Chromosomes of Triticum Turgidum by Induced Homoeologous Recombination.

“…Friebe et al (1987;1993), andMujeeb-Kazi et al (1996) transferred the wheat-rye translocation T1BL·1RS from common wheat to durum wheat. Ceoloni et al (1996) transferred Pm13 from A. longissima to chromosome 3B of durum wheat in the form of the translocation T3BL·3BS-3S l and T3DL·3DS-3S l .The same authors transferred the leaf rust-resistance gene Lr19 from A. elongatum into durum wheat in the form of the translocation T7AS-7AeS·7AeL. The translocation chromosome is not transmitted through the pollen, thus preventing the recovery of homozygous lines.…”

“…The resulting F 1 plants (345 seeds) were backcrossed with the LDN 5D(5B) substitution line in which chromosome 5B is absent and replaced by a pair of 5D chromosomes with the objective of transferring D genome Hessian fly resistance genes onto A or B genomes of T. turgidum by homoeologous recombination. A total of 2,053 segregating BC 1 F 1 plants were tested for Hessian fly resistance, and the resistant plants (1,132) were backcrossed again with LND 5D(5B) to produce BC 2 F 1 and selfed to produce BC 1 F 2 . In the BC 1 F 1 populations, 24 families segregated for an excess of resistant plants than the expected 1:1 resistant to susceptible plants suggesting that they were putative A-D genome positive recombinants.…”

“…Very little progress, however, has been made in durum wheat (Ceoloni et al, 1996;Luo et al, 1996) because the buffering ability of durum wheat is less than that of common wheat (Ceoloni et al, 1996;Joppa, 1993). Transfers from the A and B genomes of Triticum aestivum L. can be accomplished through homologous recombination, whereas transfers from the D genome or other wild relatives of wheat require enhanced pairing through induced homoeologous recombination by using ph mutant or genetic stocks where chromosome 5B is absent.…”

“…Ceoloni et al (1996) transferred the powdery mildew resistance gene Pm13 from Aegilops longissima Schaseinf. & Muschl.…”