Behaviour of an extra-fragment chromosome induced by Bassia oil inZea mays

Abstract

Maize plants raised from seeds soaked in Bassia oil frequently produced semi-sterile ears. In one case the progeny of a semi-sterile plant consisted of (1) plants with the normal number of bivalents and (2) plants with a fragment chromosome in addition to the normal number. The behaviour of the extrafragment chromosome in meiosis has been studied in detail. The origin of the fragment chromosome is also discussed. It is regarded as formed by fragmentation of a normal chromosome. This is possible on account of the frequent occurrence of fragmentation and other structural chromosome alterations in maize plants raised from seeds soaked in Bassia oil. A kernel loss of about 25% has been observed in plants having an extra-fragment chromosome. There was no evidence of an effective mechanism for progressive numerical increase of the fragment chromosome. Instead it was found that there is a significant loss of the extra-fragment chromosome from one generation to another.