Common duckweed (Lemna minor L.) is a widely used plant for phytoremediation and environment monitoring of wastewater in vivo, as this plant can be efficiently grown in Petri dishes and quickly multiplied in laboratory conditions. It is also a valuable test object to study the impact of various environmental factors by measuring growth and biochemical parameters. Our goal was to establish an axenic diploid line of L. minor free from symbionts, for use as a model plant to obtain reproducible results in experiments. In this work, we used 29 L. minor clones collected in natural conditions in Lithuania and Latvia, which were naturally inhabited with bacteria and algae. The L. minor clone entitled Sta2 was found to be best to fit requirements to establish a laboratory line suitable for testing of the genetic and physiological influence of environmental factors. Application of flow cytometry, confocal laser scanning microscopy, and sequencing of catalase, glutathione peroxidase, and ascorbate peroxidase genes proved that the selected and specifically sterilised line Sta2 was diploid and free from symbiotic bacteria or algae. Media for storage and for rapid propagation of L. minor biomass were also developed. The axenic line Sta2 can be maintained in sterile laboratory conditions and can be used as a model organism in a wide spectrum of biological and environmental investigations.
