Telling duckweed apart: Genotyping technologies for the Lemnaceae

1 Why duckweed? In his monographic study [1, 2] Elias Landolt wrote: “Within the last sixty years the family of Lemnaceae became more and more important as suitable research material for plant physiology and phytochemistry. Some of the advantages of Lemnaceae are: fast and predominantly vegetative reproduction (genetically uniform clones), only small laboratory space requirement, and aseptic culture. In addition, the family aroused attention as a food source due to its high productivity and its high protein content. Furthermore, Lemnaceae are used as multipurpose test objects and for nutrient and mineral removal from sewage water. The literature on Lemnaceae has been growing exponentially for the last 30 years. Hillman [3] cites 250 titles in his review of the descriptive and experimental literature of the family Lemnaceae. The bibliography of the present work . contains more than 3 000 titles. ” It only can be added that 25 years later the “Web of Sciences” cited more than 3 000 additional papers concerning duckweed in reviewed journals. It is thus quite apparent that the special properties of this family of aquatic plants are now capturing more interests from the scientific community worldwide than ever before. Duckweed belongs to f lowering plants but f lowering of these species is rather rare . Instead, the preferred mode of propagation is vegetative. Vegetative propagation here means that the frond primordia will start to develop and grow out of the pockets of mother plants [1, . Some duckweed (species of the genera Spirodela, Landoltia and Lemna) possess two meristematic primordia in the pockets, whereas in others (genera Wolffia and Wolffiella) daughter fronds were formed from a meristematic region in the single reproductive pouch of a mother frond . As an example, in Wolffia borealis approximately 10 daughter fronds were formed from one mother frond with a formation rate of 0.62 fronds per day . At the time of emergence of the daughter frond out from the pouches of the mother frond it contains already more or less developed primordia for the next generation of fronds. This mechanism of propagation is the basis of the exponential growth rate and responsible for the fascinating “secret of duckweed” in rapidly producing biomass. Doubling times of 2 days or less also under natural conditions are not rare in this family of plants. This high productivity is connected with high reproducibility when cultivation is carried out under standardized conditions. These properties have important implications for the practical applications of duckweed on the basis of its rapid biomass production. Duckweed biomass can be used and has already been demonstrated for the production of ethanol following saccharification of starch and fermentation of the resulting glucose . The high protein content in some strains and under alternative growth conditions makes the biomass also valuable as animal feed or human food [7, 10, . There is another important fact in duckweed cultivation: instead of fertilizing the plants with chemicals that are likely to rise in costs both economically and ecologically, duckweeds in general are adapted to eutrophic conditions and can grow well on municipal or Telling Duckweed Apart: Genotyping Technologies for the Lemnaceae Klaus J. Appenroth1, Nikolai Borisjuk2 & Eric Lam2* (1University of Jena, Institute of General Botany & Plant Physiology, Jena 07743, Germany) (2Plant Biology & Pathology, Rutgers State University of New Brunswick, NJ 08901, USA)