Microspore Abortion and Abnormal Tapetal Degeneration in a Male‐sterile Wheat Line Induced by the Chemical Hybridizing Agent SQ‐1

Abstract

ABSTRACTThis study investigated the relationship between abnormal degeneration of the tapetum and pollen abortion in an SQ‐1‐induced male‐sterile line of wheat (Triticum aestivum L.), using semithin sectioning and cytochemistry. Anthers were collected from the tetrad through trinucleate stages, and 1.5% (w/v) acetocarmine staining was used to confirm the developmental stage. Lipids, polysaccharides, and proteins were detected by staining, and the area, mean optical density, and integrated optical density of the tapetum and pollen were calculated. Microspores of the male‐sterile line had a relatively smaller area and developed more slowly than those of the fertile control anthers, indicating that they had undergone abnormal mitosis and formed abnormal sperm cells containing only one or two nuclei in the mature pollen. In addition, although degeneration of the tapetum in the male‐sterile line commenced at the tetrad stage, which was earlier than in the control, degeneration was not completed until after that in the control. Semithin sectioning indicated that nutrient accumulation was abnormal in the male‐sterile line. No polysaccharides were found in tetrads in the male‐sterile line; at the early‐uninucleate stage, and fewer lipids and polysaccharides were found in the sterile pollen compared to the control. From the bi‐ to trinucleate pollen stages, polysaccharides, lipids, and proteins were lower in pollen of the male‐sterile line than in control pollen. Therefore, SQ‐1 probably delayed tapetal degeneration in the anthers of male‐sterile plants, leading to decreased nutrient supply and pollen abortion.