Variation in the Intergenic Spacer of Ribosomal DNA of Wild Wheat, Triticum dicoccoides. In Israel

The variation in the intergenic spacer of ribosomal DNA (rDNA) of tetraploid wild emmer wheat, Triticum dicoccoides, in Israel was examined in 112 individual plants representing 12 populations tested earlier for allozymic variation encoded by 50 gene loci. The variation detected by means of restriction endonucleases results in part from variation in the number of 135-bp repeats that are in tandem array in the intergenic DNA. Intergenic spacers of genes within a single locus are relatively homogeneous, but populations of T. dicoccoides display a wide spectrum of rDNA spacer-length variation. Some populations are very homogeneous, whereas others are heterogeneous. The most homogeneous population consists of plants with spacerrDNA lengths that are the most common in T. dicoccoides in Israel. The lengths of specific regions within the spacer DNA are identical for loci on different chromosomes in the most homogeneous population. The allozymic and rDNA diversities within populations are highly and significantly intercorrelated, and both allozymic and rDNA diversities are significantly correlated with and predictable in terms of climatic variables.

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