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The F1 hybrids of T. timopheevi and
T. monococcum had 21 chromosomes (Fig.
1), and after chromosome doubling, the amphiploid of T.
timopheevi-T.monococcum had 42 chromosomes (Fig.
2). Morphologically, the amphiploid resembled the accession of T.
zhukovskyi, PGR 10370 (Fig. 3). It had
a red coleoptile, and the entire plant was pubescent. Spikes of the
amphiploid also resembled T. zhukovskyi. This amphiploid had a
laterally compressed spike and long awns and, was non-free-threshing
as a result of glumes which tightly held the grains. The spike was
tapered at the base and tip. The rachis was rather brittle, and
easily disarticulated into individual spikelets at maturity. The
spikelets disarticulated at a point above the junction of the rachis
and rachilla, and each spikelet contained two grains. Both T.
zhukovskyi and the amphiploid had long red grains (Fig.
4). T. timopheevi has been noted for its resistance to
diseases, including rusts (Knott 1989), septoria nodorum, and tan
spot (Ma and Hughes 1995), and T. monococcum has resistance to
rusts (Knott 1989). Therefore, this amphiploid derived from T.
timopheevi and T. monococcum might have resistance
to several diseases. Synthetic wheat with genome AAGGAA was
previously developed using T. timopheevi and T.
monococcum by Y. Watanabe in 1955 and T. Kawahara in 1982
(http:// www.shigen.nig.ac.jp/wheat). In the current study, the
accessions of T. timopheevi and T. monococcum
used for the development of synthetic zhukovskyi wheat are
different from those used by Y. Watanabe and T. Kawahara, and they
have some resistance to fusarium head blight (data not shown).
The development of synthetic zhukovskyi wheat not only can provide
useful germplasm for wheat breeding program but also can help
scientist study wheat evolution. An evaluation of the amphiploid for
resistance to fusarium head blight, septoria nodorum and tan spot
etc. will be carried out in the greenhouse and fields. In order to
confirm the evolution of T. zhukovskyi, a conventional
cytogenetic study will he conducted by crossing the amphiploid with
T. zhukovskyi for observation of chromosome pairing
behavior of the F1, and a molecular cytogenetic
study will also be conducted using in situ hybridization
techniques.
References
Bowden WM (1959) Taxonomy and nomenclature of wheat, barley and
rye and their wild relatives. Can J Bot 37: 657- 684.
Dvorak J, Terlizzi PDI, Zhang HB and Resta P (1992) The evolution
of polypIoid wheats: identification of the A genome donor species.
Genome 36: 21-31.
Jakubziner M (1959) A new wheat species. Proc Ist Int Wheat Genet
Symp, Winnipeg: 207-220.>
Kimber G and Sears ER (1983) Assignment of genome symbols in
Triticeae. Proc 6th Int Wheat Genet Symp, Kyoto: 1195-1196.
Knott DR (1989) The wheat rusts-breeding for resistance. in:
Frankel R, Grossman M, Linskens HF, Maliga P and Riley R (ed)
Monographs on theoretical and applied genetics (12). Springer-Verlag,
Berlin/Heidelberg: 170-171.
Ma H and Hughes GR (1995) Genetic control and chromosomal location
of Triticum timopheevii-derived resistance to septoria
nodorum, blotch in durum wheat. Genome 7: 91-97.
Upadhya MD and Swaminathan MS (1963) Genome analysis in
Triticum zhukovskyi, a new hexoploid wheat. Chromosoma 14:
589-600.
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