Anther wall development, microsporogenesis and microgametogenesis in male fertile and sterile chrysanthemum (Chrysanthemum morifolium Ramat., Asteraceae)

Anther wall development, microsporogenesis and microgametogenesis were compared between a normal male fertile chrysanthemum cultivar ‘NJAU04-29-2’ and the two male sterile selections ‘rm20-11’ (anther indehiscent) and ‘NJAU05-52-2’ (anther aborted). In both of the two male sterile types, the tapetum enlarged abnormally and showed signs of disorganization of walls at the onset of meiosis, the pollen was aborted, the anthers appeared shrunken, and the anther vascular bundle and connective tissue were degenerated by anthesis. In ‘rm20-11’, the two smaller pollen sacs began to degenerate at the microsporogenesis stage, so that only one or two microsporangia developed, while in ‘NJAU05-52-2’, only one or two microsporangia were formed following the archesporial cell stage, and most of the microspore mother cells degenerated during the course of meiosis.

Research highlights▶ Two types of male sterility in the chrysanthemum are documented. ▶ Malfunctioning of the tapetum appears in both of two types of male sterility. ▶ Absence of endothecial cell wall thickening plays a key role in anther indehiscent. ▶ Anther abortion is mainly resulted from the lack of microsporangia.