The vast majority of commercial sunflower hybrids worldwide are produced
using cytoplasmic male sterility (CMS) of the PET1 type, resulting from
the interspecific hybridization of Helianthus petiolaris with Helianthus
annuus. In this study, the open reading frame, orfH522, associated with
the CMS-PET1 phenotype, was revealed for the first time in the
3’-flanking region of the mitochondrial atpA gene in wild H. annuus. An
analysis of whole genome data from 1089 accessions showed that the
frequency of occurrence of CMS-orfH522 in wild H. annuus populations is
3.58%, while in wild H. petiolaris populations, it is 1.26%. The
presence of additional genomic data with insufficient coverage of the
orfH522 sequence indicates that the potential frequency of occurrence of
CMS-orfH522 in natural sunflower populations may be two times higher.
Based on these results and previous studies, PET1-CMS was suggested to
be a natural cytotype of H. annuus, and the appearance of the CMS
phenotype in cultivated sunflowers is associated with the loss of
stabilizing nuclear genes of fertility restorers, which occurred during
interspecific hybridization. These data may explain the patterns of
differential cytoplasmic and nuclear introgression occurring in wild
sunflower and are useful for further evolutionary studies.