| A number of Hordewa and Triticum species and varieties have
now been intercrossed and cytological peculiarities have been reported for
a number of these combinations. The hybridization of Chinese Spring by H.
bulbosum is followed by a sequential elimination of chromosomes of the
latter at a post zygotic stage (BARCLAY, 1975). At later stages such as
mitotic metaphase in hybrids between H. vulgare cult. Manker x T.
turgidum, chromosomal instability is manifest as anaphase bridges, aberrant
chromatid separation and finally somatic cells with chromosome numbers of
14, 16, 17, and 18 instead of the expected number of 21 (MUJEEB et al.,
1978). And finally, abnormalities at gametogenesis such as those reported
herein occur at still later stages. Thus far, there are no reports of chromosome doubling in Hordeum x Triticum hybrids to produce fertile amphiploids. It is possible that the chromosomal instability described for the hybrid material may persist in the amphiploids, thus affecting gametogenesis and reducing fertility. In view of this possibility, a more practical approach to the transfer of alien loci between species may be the manipulation of meiotic pairing control genes to affect recombination followed by backcrossing and selection of desired traits rather than the production of the raw amphiploids. Literature Cited BARCLAY, I.R. 1975. High frequencies of haploid production in wheat (Triticum aestivum) by chromosome elimination. Nature 256 : 410-411. CAUDERON, Y., G. TEMPE and G. GAY 1978. Creation et analyse cytogenetique d'un nouvelle hybride : Hordeum vulgare ssp. distichon x Triticum timopheevi. C.R. Acad. Sci. 286 : 1687-1690. FEDAK, G. 1977a. Increased homoeologous chromosome pairing in Hordeum vulgare x Triticum aestivum hybrids. Nature (London) 266 : 529-530. FEDAK, G. 1977b. Barley-wheat hybrids. Interspecific hybridization in plant breeding. Proc. 8th Cong. EUCARPIA, Madrid, pp. 261-267. FEDAK, G. 1980. Meiosis in reciprocal barley-wheat hybrids. Can. J. Genet. Cytol. 22:117-123. ISLAM A.K.,K.W. SHEPHERD and D.H.B. SPARROW 1975. Addition of individual barley chromosomes to wheat. Barley Genetics III Proc. 3rd. Int. Balrey Genet. Symp., Garching, W. Germany pp. 260-270. MUJEEB K.A.,J.B. TOHOMAS, R. RORDIQUEZ, R.F. WATERS and L.S.Bates 1978. Chromosome instability in hybrids of Hordeum vulgare L, with Triticum turgidum and T. aestivum. Jour. Heredity 69: 179-182. |
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