Development of novel perennial Sorghum bicolor x S. propinquum hybrids
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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 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 S. propinquum F population for height, tillering capacity, days to flowering, and overwintering capacity. Our research identified F hybrids exhibiting transgressive segregation for height, whereas hybrids were intermediate between the parental extremes for days to midanthesis and tillering capacity. Fortuitous harsh winter conditions in 2018 applied strong natural selection pressure for overwintering capacity, allowing for the identification of F 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.