Identification and cytological observation of CMS in cotton

Abstract

Background The utilization of male sterility is essential for producing hybrid seeds, and comprehending the mechanism of male sterility is the foundation for developing sterile germplasm resources. However, only a few cytoplasmic male sterility (CMS) lines of cotton have been produced due to various hindrances. Inadequate agronomic traits and incomplete sterility, weak resilience of restorer lines and the difficulty in combining strong dominance all serve as primary impediments to the advancement of CMS in cotton. Therefore, identifying and cytologically observing of CMS in cotton will provide new insights for heterosis utilization. Results Two F2 segregating populations of cotton were constructed from cytoplasmic sterile lines (HaA and 01A, maternal) and restorer lines (HaR and 26R, paternal). Genetic analysis of F2 segregation populations showed that the separation ratio of fertile to sterile plants was 3:1. Phenotypic analysis indicated that there was no significant difference in the development process of flower buds between sterile and fertile plants. Compared to fertile plants, sterile plants exhibit smaller floral organs, shortened filament length and anther atrophy on the day of flowering. Scanning electron microscopy (SEM) of two F2 populations revealed morphological variations in the folds of the anther epidermis. Analysis of cell level differences showed that there was no significant difference in pollen development before the pollen maturation stage. However, between pollen maturation stage and flowering stage, the tapetum layer of sterile plants degenerated prematurely, the pollen grains were abnormal, pollen cytoplasmic degradation and gradually hollowed out. Conclusion The sterile trait is controlled by a single recessive gene. The floral morphology of the sterile plant was characterized by stamen atrophy and abnormal anthers. Pollen abortion occurs from the time of pollen maturity until flowering. Degradation of pollen grains and the formation of empty pollen grains due to the premature degradation of the tapetum are presumed to be the main cause for pollen abortion.