Abstract
The St genome of Pseudoroegneria (Triticeae, Poaceae) not
only accounts for more than 60% perennial speciation, but also
prominent for forage and crop breeding. The diploidPseudoroegneria libanotica with more ancient St genome is covered
by cuticular wax on the aerial part, and exhibited strong drought
resistance. To reveal the genetic relationship among Triticeae species
and illustrate the mechanism between water deficit and cuticular wax
formation, in this study, we (1) assembled the chromosome level St
genome of Pse. libanotica with 2.99 Gb assembled into seven
pseudochromosomes; less repeat clusters (TEs) is the main reason for the
St genome with smaller genome size, and high genome heterozygosity might
cause abundant St-containing speciation; (2) the genusPseudoroegneria diverged during the middle and late Miocene, and
unique genes, gene family expansion and contraction in Pse.
libanotica were enriched in biotic and abiotic stresses, such as fatty
acid biosynthesis which may be greatly contribute to the its drought
adaption; (3) in total, 14 genes were involved in wax biosynthesis under
28 days drought treatment, more importantly, a new Kcs geneevm.TU.CTG175.54 plays a critical role in the very long chain
fatty acid (VLCFA)elongation from C18 to C26 inPse. libanotica. Our study lays a foundation for the genome
diversification of Triticeae species and deciphers cuticular wax
formation genes that have contributed to the drought resistance ofPse. libanotica.