Cytological and Ploidy Analyses Revealing Fertility Defects of Cultivar Cyperus esculentus L. in China

Cyperus esculentus L., commonly known as Yellow Nutsedge or Tiger Nut, belongs to the Sedge family (Cyperaceae), which is widely distributed in tropical and temperate regions around the world. The species is particularly noted for its underground tuber, which is rich in starch and oil, and can be used for both food and industrial purposes. However, cultivated C. esculentus rarely flowers in the field, and when it does, flowering is often accompanied by sterility, significantly hindering the development of superior varieties through sexual hybridization. Our investigation into the causes of pollen abortion in C. esculentus yielded several key findings. Initially, we observed pollen abortion within the anthers using Alexander's red staining and starch-iodide staining techniques. Further examination through semi-thin sections of the anthers revealed that, although the pollen appeared normal during the pachytene stage, the pollen failed to stain blue in later developmental stages, indicating abnormal development. This was followed by vacuolation, collapse, and degradation of the pollen, ultimately resulting in abortion. Additionally, we monitored chromosome behavior throughout meiosis and observed premature chromosome separation during metaphase II, leading to disarray in the subsequent pseudomonad phase. Chromosomal karyotype analysis and ploidy predictions suggested that the triploid nature of C. esculentus contributes to meiotic disorders, which may explain the phenomenon of pollen abortion. These findings provide valuable insights into the reproductive challenges faced by this species and may inform future breeding efforts aimed at overcoming its sterility.