Cytological study on haploid male fertility in maize

Abstract

Doubled haploid (DH) breeding technology, which relies on haploid genome doubling, is widely used in commercial maize breeding. Spontaneous haploid genome doubling (SHGD), a more simplified and straightforward method, is gaining popularity among maize breeders. However, the cytological mechanism of SHGD remains unclear. This study crossed inbred lines RL36 and RL7, which have differing SHGD abilities, with inducer line YHI-1 to obtain haploid kernels. The meiotic processes of pollen mother cells (PMCs) in the haploid plants were compared with diploid controls. The results suggested that three main pathways, the early doubling of haploid PMCs, the first meiotic metaphase chromosomal segregation distortion, and anomaly of the second meiosis, are responsible for SHGD. Furthermore, flow cytometry analysis of ploidy levels in leaves and PMCs from haploids and diploid controls revealed that somatic cell chromosome doubling and germ cell chromosome doubling are independent processes. These findings provide a foundation for further studies on the underlying mechanism of SHGD, aiding the application of DH technology in maize breeding practices.