In newly formed allopolyploids, meiotic instability in early generations contributes to reduced fertility, but less is known about their mitotic accuracy and somatic instability. Here, the authors report somatic numerical chromosome variation (somatic aneuploidy) among different individuals of newly synthesized wheat–Aegilops triuncialis amphiploids (AABBDDUtUtCtCt genome) over three successive generations. In total, 21 seeds in the F2 to F4 generations descended from three different F1 hybrids (2n = 5x = 35, ABDUtCt genome) were analyzed by chromosome counting and fluorescent in situ hybridization. Somatic aneuploidy was detected in 17 (81%) investigated individuals. Somatic chromosome numbers of the cells (among and within the evaluated individuals) ranged from 62 to 70. Furthermore, flow cytometry revealed variation in genome size within and between individual amphiploids that may be due to variable chromosome numbers. There was no evidence that somatic aneuploidy leads to stable cytotypes, at least in the early generations. The authors conclude that both newly formed status and large genome sizes may contribute to somatic and meiotic instability in synthetic wheat–Aegilops triuncialis amphiploids.
