Development of novel perennial Sorghum bicolor x S. propinquum hybrids

Sorghum species provide a unique opportunity to develop perennial cropping systems due to their interspecific hybridization compatibility and phenotypic plasticity from annual to perennial life cycle. Sorghum bicolor (L.) Moench is a diploid (2n = 2x = 20) annual species that does not produce rhizomes, whereas Sorghum propinquum (Kunth) Hitchc. is a diploid (2n = 2x = 20) perennial, rhizomatous species native to Asia and is considered a wild relative of S. bicolor. Because of their relatively close taxonomic relationship, S. bicolor x S. propinquum hybrids offer both valuable insights between annuals and perennials, as well as hybridization opportunities for the introgression of perennialism into a major cereal crop. The objective of this study was to characterize a novel S. bicolor x S. propinquum F-2 population for height, tillering capacity, days to flowering, and overwintering capacity. Our research identified F-2 hybrids exhibiting transgressive segregation for height, whereas hybrids were intermediate between the parental extremes for days to mid-anthesis and tillering capacity. Fortuitous harsh winter conditions in 2018 applied strong natural selection pressure for overwintering capacity, allowing for the identification of F-2 hybrids with greater overwintering capacity than S. propinquum. The present results provide both novel perennial sorghum germplasm resources and insight towards developing effective breeding programs for perennial cereal cropping systems.