THE ADDITION OF SINGLE CHROMOSOMES OF AVENA HIRTULA TO THE CULTIVATED HEXAPLOID OAT A. SATIVA
Six of the possible seven single chromosome addition lines of the wild diploid species A. hirtula to the cultivated oat A. sativa have been identified. The effect of the single hirtula chromosome on the morphology of the recipient A. sativa variety Manod was variable depending on the chromosome involved and certain genes which are dominant at the diploid level were only partly expressed in the hexaploid background.The frequency with which the hirtula chromosomes paired with their equivalent chromosomes in A. sativa was less than that observed in primary trisomics, indicating that the hirtula As genome is only partly homologous with the A genome of the hexaploids. None of the disomic addition lines was sufficiently stable cytologically to maintain the line without the reversion of a proportion of the progeny to the monosomic condition and eventually to the euploid chromosome number of A. sativa.