Intraspecific variation in C-banded chromosomes of Aegilops comosa and Ae. speltoides

Intraspecific variation in C-banding patterns can be used to differentiate subspecies of Ae. comosa, i.e. eu-comosa and heldrechii, but not those belonging to Ae. speltoides. Among the eu-comosa accessions, comosa E appears to possess a totally different karyotype as well as banding pattern. Two contrasting types of polymorphic changes were found. The first and more common type, observed in the 2 subspecies of Ae. speltoides and 2 accessions of Ae. comosa ssp. eucomosa, involved variation in C-band size and presence or absence of interstitial, terminal and proximal bands within a basic recognisable pattern. The second type involved complete repatterning of C-bands and could be seen in Ae. comosa where the ssp. eu-comosa has predominantly interstitial C-bands in contrast to centromeric and telomeric bands in the other ssp. heldrechii. Furthermore, the extent of polymorphic variation was found to vary between chromosomes of Ae. speltoides. That polymorphic changes have occurred without loss of fertility in hybrids between subspecies of each of the 2 species confirms that these sorts of changes have no effect on chromosome pairing or fertility. Polymorphic changes appear to be widespread within and between diploid Aegilops species and their non-random distribution seem to suggest that these changes could perhaps be intimately associated with the processes of speciation and subspeciation.