Chromosomal abnormalities in maize regenerants in R1
--Kravchenko OA, Lysikov, VN, Palii, AF

We have previously reported (MNL 71:42-43) on the effect of gamma radiation on callus formation and somatic embryogenesis. It was found that the influence of gamma radiation was reliable and resulted in decreasing of callusogenesis and somatic embryogenesis frequency. We are now extending these studies to plant regenerants and the R1 generation. The experiment was carried out as follows: seeds of regenerants obtained from immature irradiated (4 Gr) embryos of inbred line 346 culture were germinated. Rootlet samples were fixed in 3:1 ethanol:acetic acid and standard 2% acetocarmine squash preparations were made to study and calculate various chromosomal abnormalities. Cytological analysis demonstrated that bridge and fragment formation as well as chromosome lagging was observed during anaphase and telophase of mitosis and occurred with variable frequencies (Table 1). It should also be noted that the maximum lethality proved to be among regenerants with a higher chromosomal abnormality frequency, especially in early stages of ontogenesis. In addition, male gametophyte viability of regenerants that reached flowering stage was 70.73%-72.51%. The results obtained indicate that chromosomal abnormalities induced by gamma radiation appear to remain at a rather high level in culture conditions in vitro and among regenerants in R1.

Table 1. Chromosomal abnormalities of regenerants in R1.
 
Types of abnormalities Frequency, %
bridges 1.34-3.11
fragments 0.91-3.89
lagging 2.86-14.81


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