High bivalent frequencies in artificial autopolyploids of Hyoscyamus muticus L.

Abstract

High pollen and seed fertility of induced autotetraploids of the medicinal solanaceous plant Hyoscyamus muticus (4x = 56) could, at least in part, be attributed to low quadrivalent and high bivalent frequencies at metaphase I (MI). Mean configuration frequencies per cell were 3,45 ring quadrivalents, 0.49 chain quadrivalents, 0.55 trivalents, 5.98 ring bivalents, 12.67 open (rod) gbivalents, and 1.34 univalents. In the diploid, ring bivalents were most common with chiasmata predominantly distal at diakinesis-MI. Different causes can explain the low quadrivalent frequencies in the tetraploids. Using a simple algebraic model, calculations show that the most probable explanation is reduced chiasma formation in one arm per chromosome, resulting from nonmedian partner exchange and special interference patterns. This agrees best quantitatively with high open (rod) bivalent frequencies compared with the diploid, accompanied by high ring quadrivalent frequencies.