Chenopodium polyploidy inferences from Salt Overly Sensitive 1 (SOS1) data

Area of Science:

• Plant evolutionary biology
• Genomics
• Phylogenetics

Background:

• Chenopodium (Amaranthaceae) is a diverse genus with agriculturally important crops and weeds.
• Polyploid species within Chenopodium have complex evolutionary histories.
• Understanding their origins is crucial for crop improvement and weed management.

Purpose of the Study:

• To construct a robust phylogeny for Chenopodium using nuclear DNA.
• To clarify the evolutionary relationships among polyploid species.
• To identify the genome donors of important polyploid Chenopodium species.

Main Methods:

• Phylogenetic analysis of two introns from the single-copy nuclear locus Salt Overly Sensitive 1 (SOS1).
• Direct sequencing of diploid species.
• Plasmid-mediated cloning to separate homeologous sequences in polyploids.
• Maximum likelihood and Bayesian phylogenetic analyses.

Main Results:

• Polyploid homeologous sequences were resolved into four clades (A-D).
• Two independent polyploid lineages were identified: American tetraploids (A, B homeologs) and Eastern Hemisphere hexaploids (B, C, D homeologs).
• The American diploid C. standleyanum was identified as the closest relative to the A genome donor of American tetraploids, including quinoa.

Conclusions:

• The two major polyploid lineages in Chenopodium originated independently.
• Each polyploid lineage likely arose from a single origin event.
• C. standleyanum is a significant resource for quinoa breeding programs.
• The placement of C. bryoniifolium suggests transoceanic dispersal within the genus.