Frequency of Aneuploids in Autotetraploid Populations of Italian Ryegrass (Lolium multiflorum Lam.)

Abstract

The frequencies of aneuploids and meiotic behaviours were studied in early and advanced generations of induced autotetraploid Italian ryegrass. The mean proportions of aneupl.oids were 59% in early generation and 47% in advanced generation, and the difference between them was significant. But, the populations selected by snow endurance, though those were in advanced generation, had aneuploids as frequently as those in early generation. A higher frequency of bivalents and lower frequency of quadrivalents were found in advanced generation than in early generation. It is estimated that the frequencies of aneuploids in each population of advanced generation have been already reached in equilibrium state, and, this equilibrium value is variable in relation to the fitnesses of aneuploids and euploids.