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cytogenetic variation was reporlod in rMcum aesh'vum (wheat) by Ahloowallo (1982) who
explainr the presence of aneuplold chromosome numban in the callus cells and also
univalent laggards, chromatin bridges, fragments at Anaphase I, and micronuclei In tetrads
of regenerdd plank to the occurrence of chromosomal Inversions and deletions. The
observed voridion in morphology, like pollen sterility and reduced seed weight, was thus
explained by a loss or gain of a whole chromosome or structural changes In chromosomes.
Karp and Maddock (1984) reporled 27% of regenerants to be ancwplolds. Some d the
regenerants were also observed to show chromosomal structural changes, particularly
interchanges. Davles et al. (1986) correlated 13 of the 17 regenerants (from a total of 551)
having altered ADHl zymogram with aneuploidy. The red of the 4 were observed to give rise
to euplold progeny. 3 of which were interpreted to possess o 4a Isochromosome, a 3BSJ4Aa
franslocotion and a 78SJ4Aa translocation respectively. Galiba et al. (1985) observed euploid
chromosome number of 2n~6x.42, while in 3 somaclonal families the chromosome number
ranged from 41 to 45 with some plants also containing telocentrlcs.
Regenerated plants with aberrant cytology were also observed in Avena sotlva (oak) by
McCoy et al. (1982) who repori an increase in trequency of chromosomal variabilliy horn 12-
49% to 48-88% with increase In duration of culture. Betides chromosome breclkage ond loos
of chromosome segments, lrisomy, monosomy, interchanges and inversions were also
observed. Also in oat, Maddock and Semple (1986) observed euploid chromosome number
of 42 and aneuplold plants that were shorier and darker green in colour. In about 9% d the
cells In progeny of two regenerated oat plants, premature reparation d hetemmorphlc
blvalents and lagging during anaphoro I were observed by Johnton et al. (1987a). In a later
Study Johnson et al. (1987b) discussed the possible role of heterochromatln In chromorome
breakage Induced In oat tissue cultures. They suggest that the prerence ol pmxlmal and
telorneric hetwochromatln means that bridges resumng fmm repllcdion problem in thew