Cytological observation of anther development of cytoplasmic male sterility and thermosensitive genic male sterility systems in rice
Male sterility is an excellent tool for use in hybrid rice production as it involves naturally occurring emasculation of the male gamete, thus preventing self-pollination in plant species. There are two male sterility systems—cytoplasmic male sterility (CMS) and thermosensitive genic male sterility (TGMS) —being widely used in rice breeding programs. Although TGMS and CMS systems are valuable tools for rice breeding, and the genetic and molecular mechanisms in various plants have been extensively studied, knowledge of the critical stage of cellular change in the rice anther is still imprecise. To gain an understanding of the actual crucial developmental stage of the rice anther that affects pollen productivity, cytological events were observed throughout the anther developmental process in both TGMS (KUT1) and CMS (IR80151A) rice lines. The results revealed that male sterility in the KUT1 line was most pronounced in the late meiotic stage during the developmental process and ultimately resulted in empty locules that were without pollen grains. In the IR80151A line, male sterility was displayed at the late vacuolated stage and consequently caused pollen abortion. Therefore, it was concluded that male sterility of CMS and TGMS occurs post meiosis.