Gametoclonal variation detected in the nuclear ribosomal DNA from doubled haploid lines of a spring wheat (Triticum aestivum L., cv. ?C sar?)

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Abstract
The organization of the nuclear ribosomal DNA from a parental line of wheat (Triticum aestivum L., cv. ‘César’) and its anther-derived first cycle and second cycle doubled haploid lines has been analyzed by DNA-DNA molecular hybridization. Restricted DNA has been probed by three subclones of wheat nuclear ribosomal DNA covering the entire repeat unit. No significant difference was detected in the extent of methylation of ribosomal DNA of the doubled haploid lines with respect to the parental line. On the other hand, a variation has been found in the organization of the nontranscribed spacer region of ribosomal DNA of the first cycle doubled haploid line. This variation remains stable after a second cycle of in vitro androgenesis. However, one out of five second cycle doubled haploid lines so far tested showed an additional hybridization band present in the parental line but lacking in the first cycle doubled haploid line.