Genetic and epigenetic regulation of male fertility restoration in the 9E, A4 and M35 CMS-inducing cytoplasms of sorghum

The use of new CMS-inducing cytoplasms significantly increases the genetic variability of cultivated sorghum hybrids. The aim of the research was to study the inheritance of fertility restoration in new types of male-sterile cytoplasms (A4, 9E, M35) and to explore the reasons for its instability. Genetic analysis revealed that the restoration of male fertility was controlled by dominant genes, whose expression was strongly dependent on a sufficient level of water availability to plants during anther and pollen formation. An epigenetic mechanism for "switching on" fertility-restoring gene expression in F sub(1) hybrids is proposed, which is regulated by water availability to plants. This "active" state of fertility-restoring genes is stably expressed in self-pollinated progenies of restored hybrids, irrespective of their water availability conditions, but is not transmitted to testcross hybrids grown under arid conditions.