Origin of the Rare Hybrid Genus xTrisetokoeleria Tzvelev (Poaceae) According to Molecular Phylogenetic Data

In our article, we analyzed new data on the origin of the hybrid genus xTrisetokoeleria. According to the morphological criteria xT. jurtzevii is a hybrid between Koeleria asiatica s. l. and Trisetum spicatum, xT. taimyrica, and originated from Koeleria asiatica s. l. and Trisetum subalpestre, xT. gorodkowii, a hybrid between Koeleria asiatica and Trisetum ruprechtianum. Later xT. taimyrica was transferred to Koeleria. Parental taxa are prone to active hybridization themselves, thus, new methods of next-generation sequencing (NGS) were needed to clarify the relationships of these genera. For NGS we used the fragment 18S rDNA (part)-ITS1-5.8S rDNA (totally 441 accessions). We analyzed ITS1-5.8S rDNA-ITS2 region, trnL-trnF and trnK-rps16 from eight samples of the five species, using the Sanger method: xTrisetokoeleria jurtzevii, xT. taimyrica, Koeleria asiatica, Sibirotrisetum sibiricum (=Trisetum sibiricum), and Trisetum spicatum. We also studied the pollen fertility of xTrisetokoeleria and its possible progenitors. Our data partly contradicted previous assumptions, based on morphological grounds, and showed us a picture of developed introgression within and between Koeleria and Trisetum. xT. jurtzevii, a totally sterile hybrid formed rather recently. We can suppose that xT. jurtzevii is a hybrid between K. asiatica and some Trisetum s. str. Species, but not T. spicatum. xT. gorodkowii, a hybrid in the stage of primary stabilization; it has one unique ribotype related to T. spicatum s. l. The second parental species is unrelated to Trisetum ruprechtianum. xT. taimyrica and is a stabilized hybrid species; it shares major ribotypes with the T. spicatum/T. wrangelense group and has a minor fraction of rDNA related to genus Deyeuxia s. l.

Automated summary

In our article, we analyzed new data on the origin of the hybrid genus xTrisetokoeleria. The results showed that xT. jurtzevii is a hybrid between Koeleria asiatica and Trisetum spicatum, xT. taimyrica originated from Koeleria asiatica and Trisetum subalpestre, and xT. gorodkowii is a hybrid between Koeleria asiatica and Trisetum ruprechtianum. Next-generation sequencing methods were used to clarify the relationships between these genera. The study also provided insights into the pollen fertility of xTrisetokoeleria and its possible progenitors.