Establishing a chromosome map for Spirodela polyrhiza, chromosome homeology and karyotype evolution within the aquatic, largely asexual Lemnoideae, a basic monocot group of potential economic importance

• Applicant: Professor Dr. Ingo Schubert
• Subject Area: Plant Genetics and Genomics
• Term: from 2014 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 256417479

Lemnoideae, a monophyletic subfamily within the monocot order Alismatales, are small and phenotypically simple free-floating aquatic organisms with very fast vegetative propagation. Therefore, some species are considered for efficient biomass production to generate biofuel, to feed livestock and (simultaneously) to clean waste water. The Lemnoideae comprise 5 genera of together 37 species. The genome of Spirodela polyrhiza has been sequenced as a reference for Lemnoideae genomes. We have confirmed the small genome size (158 Mbp/1C), and 2n=40 chromosomes for this species. The aim of the proposal is to establish the genetic composition, diversity and evolution of karyotypes for S. polyrhiza, and for representative species of all five genera, displaying variable genome sizes and chromosome complements. Because of rare sexual propagation and lacking genetic maps, the genomic contigs (which we confirmed and partially corrected) of S. polyrhiza need to be arranged into 20 linkage groups by means of in situ hybridisation. Then, comparative chromosome painting, based on chromosome-specific S. polyrhiza BAC pools, will reveal chromosome homeology and karyotype diversity and evolution (inter- and intrachromosomal rearrangements, ploidy mutations) between natural clones of S. polyrhiza and other Lemnoideae species that display different genome sizes and/or chromosome numbers as well as different body size and degree of neotenisation. Such comparison would be much more intricate by other techniques. Our approach will elucidate the genetic diversity between vegetative clones of duckweeds and provide a reliable basis for application-oriented research on this under-investigated potential crops.

• DFG Programme: Research Grants