Further Evidence of Meiotic Instability Induced by Atrazine in Grain Sorghum

Abstract

Two sorghum inbreds (Combine Kafir 60 and Combine 7078) and their F1 and F2 progenies were treated with atrazine, as a preemergence herbicide, at 3, 6, and 9lb/A (3.3, 6.6, and 10.0 kg/ha). Low frequencies of meiotic aberrations occurred in all treated populations; no aberrations were observed in control populations. Frequency of total aberrations seemed higher in the F1 than in the F2 or parental lines; irregularities seemed more frequent in Combine 7078 than in Combine Kafir 60. More common aberrations were aneuploidy, polyploidy, metaphase I univalents, and multinucleate cells; anaphase I bridges and telophase I laggards were less frequent.Significance of these findings is not clear. A primary cause for concern is that irregularities of the kind observed may enhance development of offtypes and thereby create problems of genetic instability in lines or cultivars. The possibility that atrazine has similar effects on weeds also is worrisome. On the other hand, observed abnormalities were rare and have not been shown to result in viable offtypes or to be associated with reduced genetic stability in treated populations. Results should not be interpreted as militating against the use of atrazine or similar herbicides but as indicating a need for further investigation of the effects of such chemicals on the reproductive mechanisms and genetic stability of plant populations.