Abstract
The utilization of crop hybrids plays an important role in crop breeding and production, and the innovation of the male sterile germplasm is the basis for this utilization. However, the utilization of hybrid advantage in cotton is currently dominated by cytoplasmic male sterility (CMS) lines in Harknessi cotton, which has a single cytoplasmic origin and exhibits a significant negative effect of cytoplasmic-nuclear interactions. The negative effect of cytoplasmic-nuclear interactions can only be minimized by selecting and breeding CMS lines in which the cytoplasm and nucleus originate from the same variety. However, no homologous cytoplasmic-nuclear CMS germplasm has been created, and its mechanism of occurrence has not been determined. In this study, two homologous cytoplasmic-nuclear CMS lines and two heterologous cytoplasmic-nuclear CMS lines were utilized, and the heterologous cytoplasmic-nuclear CMS lines were aborted at a relatively early stage. The physiological indexes related to reactive oxygen species (ROS) metabolism in the heterologous cytoplasmic-nuclear CMS lines were lower than those of the homologous cytoplasmic-nuclear CMS lines, including the enzyme activities of POD and CAT from the tetrad to the mature pollen grain period, and the metabolite content of malondialdehyde (MDA) was inversely correlated with the enzyme activities of the heterologous cytoplasmic-nuclear CMS lines. Resequencing analysis of four cotton mitochondrial genomes (mt genomes) revealed that the heterologous cytoplasmic-nuclear CMS lines were more complex than the homologous cytoplasmic-nuclear CMS lines, and the homologous CMS lines showed a higher degree of covariance with the maintainer lines. This indicates that heterologous cytoplasmic-nuclear interactions are more likely to lead to mtDNA structural variation. Taken together, the results showed that the cytoplasmic-nucleus homologous system was less affected by the cytoplasmic-nuclear interaction and was the best combination for the study of male sterility.