Abstract

Maize seedlings of the genotype C I Sh Wx were fumigated with hydrogen fluoride gas (HF) continuously for 4, 6, 8 and 10 days. Miscrospore mitosis of the treated plants indicated the presence of fragments and bridges suggesting the occurrence of the phenomenon of breakage-fusion-bridge cycle of McClintock. This phenomenon was later confirmed by the production of endosperm mosaicisms. The period of fumigation was clearly related to the extent of the area resulting from the B-F-B cycle. Recombination values were estimated from F2 data for the regions C-sh and sh-wx. There was a significant increase in the frequency of crossing over for region I with maximum increase being for the 4 days duration. The recombination value for region II showed no significant deviation from the control. These findings indicate that HF in addition to being a mutagenic agent is also able to reduce crossing over in certain chromosome segments.

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