Abstract:

The study of sorghum (Sorghum bicolor L. Moench) A₂ cytoplasm male sterility is significant for utilizing sorghum heterosis and preventing potential disasters caused by employing sole cytoplasm source. The cytoplasm of sorghum A₂ cytoplasm-male sterility (CMS) came from IS12662C, and the hybrids with A₂ cytoplasm have been released for commercial use. Study on meiosis is very useful for understanding CMS male sterility and improving male sterile lines. In this study, A₂/B₂V4 were used to study the processes of microspore abortion during anther development and investigate the chromosomal behaviors of meiosis in A₂ CMS by cytological observation. For observing anther development, sorghum florets at various development stages were taken, fixed in FAA and observed with an Olympus microscope after staining, paraffin-bedded sliding. For observing chromosome behavior in PMC, florets were taken, fixed with Carnoy’s fixation, squashed on a slide and observed with an Olympus microscope. Many abnormal phenomena were observed during A₂ CMS anther development which were as follows: (1) no tapetal cells were formed or tapetam collapsed at very early stage during the microsporogenesis, and tapetal cells deformed; (2) although tapetal cells developed normally, meiotic behavior of chromosomes in pollen mother cells (PMC) were abnormal, leading to the degeneration of microspores; (3) the abnormal chromosomal behavior occurred in PMC meiosis of A₂ CMS started from anaphaseⅠ; (4) homologous chromosome movement to opposite poles at metaphaseⅠ was delayed or sister chromatids did not divide at metaphaseⅡ; (5) chromosomes multiploidized, and several nuclei or nucleoli were found in one cell. The abortion of taptal cells was not the only reason but for the failure of microspore, but all of above abnormalities lead to the failure of normal microspore development.

Key words: Sorghum, A₂ Cytoplasmic-male sterility, Tapetum, Meiosis