Chromosome identification and nuclear architecture in triticale × tritordeum F1hybrids

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Abstract
In situ hybridization with cloned, repetitive DNA probes and total genomic DNA enables the parental origin of all chromosomes to be established in metaphases of triticale × tritordeum F1 hybrids (2n=6x=42). Nuclei contain seven chromosomes of Hordeum chilense origin, seven from Secale cereale and 28 of wheat origin. When used as a probe, total genomic rye DNA labelled the rye chromosomes strongly and uniformly along their lengths, with brighter regions coincident with the terminal heterochromatin. The probe labelled the wheat-origin chromosomes weakly and was almost undetectable on the H. chilense-origin chromosomes. In contrast, under the same conditions, H. chilense DNA hybridized strongly to the H. chilense- and, with intermediate strength, to the S. cereale-origin chromosomes, excluding the subtelomeric heterochromatin: it hybridized only weakly to the wheat chromosomes, in some experiments revealing characteristic bands on wheat chromosomes. Cloned repetitive DNA probes from rye and H. chilense were used as probes to identify the linkage groups of all of their own-species chromosomes. Analysis of hybridization patterns of various probes to prophase and interphase nuclei indicated that there are many non-random features in the localization of both repetitive DNA and whole chromosomes, although general patterns of nuclear organization have yet to emerge. Both the particular lines used and the techniques developed here are likely to be valuable for production and characterization of plant breeding material.

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