New Insights into Interspecific Hybridization in Lemna L. Sect. Lemna (Lemnaceae Martinov)

Duckweeds have been increasingly studied in recent years, both as model plants and in view of their potential applications as a new crop in a circular bioeconomy perspective. In order to select species and clones with the desired attributes, the correct identification of the species is fundamental. Molecular methods have recently provided a more solid base for taxonomy and yielded a consensus phylogenetic tree, although some points remain to be elucidated. The duckweed genus Lemna L. comprises twelve species, grouped in four sections, which include very similar sister species. The least taxonomically resolved is sect. Lemna, presenting difficulties in species delimitation using morphological and even barcoding molecular markers. Ambiguous species boundaries between Lemna minor L. and Lemna japonica Landolt have been clarified by Tubulin Based Polymorphism (TBP), with the discovery of interspecific hybrids. In the present work, we extended TBP profiling to a larger number of clones in sect. Lemna, previously classified using only morphological features, in order to test that classification, and to investigate the possible existence of other hybrids in this section. The analysis revealed several misidentifications of clones, in particular among the species L. minor, L. japonica and Lemna gibba L., and identified six putative ‘L. gibba’ clones as interspecific hybrids between L. minor and L. gibba.