Genomic constitution of the allo-octoploid Elymus tenuis (Poaceae: Triticeae) of New Zealand

Elymus tenuis (Buch.) A. Love et Connor is a perennial octoploid (2n = 56) wheatgrass endemic to New Zealand. To investigate its genomic constitution, four artificial interspecific hybrids between E. tenuis and E. enysii (2n = 4x = 28, HW), and E. solandri (2n = 6x = 42, StYW) and E. multiflorus (2n = 6x = 42, StYW) were studied cytologically. Meioses in pollen mother cells (PMCs) of the hybrids showed relatively high chromosome pairing, with an average of 13.50 in E. enysii x E. tenuis, 20.22 in E. solandri x E. tenuis, 19.62 in E. multiflorus x E. tenuis, and 20.00 in E. tenuis x E. multiflorus bivalents per cell, respectively. The results indicate that E. tenuis is an allo-octoploid species, with the new and unique genomic constitution StYHW. An autochthonous origin is proposed for it.