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Background The plant body in duckweed species has undergone reduction and simplification from the ancient Spirodela species towards more derived Wolffia species. Among the five duckweed genera, Wolffia members are rootless and represent the smallest and most reduced species. A better understanding of Wolffia frond architecture is necessary to fully explore duckweed evolution. Results We conducted a comprehensive study of the morphology and anatomy of Wolffia globosa, the only Wolffia species in China. We first used X-ray microtomography imaging to reveal the three-dimensional and internal structure of the W. globosa frond. This showed that new fronds rapidly budded from the hollow reproductive pocket of the mother fronds and that several generations at various developmental stages could coexist in a single W. globosa frond. Using light microscopy, we observed that the meristem area of the W. globosa frond was located at the base of the reproductive pocket and composed of undifferentiated cells that continued to produce new buds. A single epidermal layer surrounded the W. globosa frond, and the mesophyll cells varied from small and dense palisade-like parenchyma cells to large, vacuolated cells from the ventral to the dorsal part. Furthermore, W. globosa fronds contained all the same organelles as other angiosperms; the most prominent organelles were chloroplasts with abundant starch grains. Conclusions Our study revealed that the reproductive strategy of W. globosa plants enables the rapid accumulation of biomass and the wide distribution of this species in various habitats. The reduced body plan and size of Wolffia are consistent with our observation that relatively few cell types are present in these plants. We also propose that W. globosa plants are not only suitable for the study of structural reduction in higher plants, but also an ideal system to explore fundamental developmental processes of higher plants that cannot be addressed using other model plants.

In 2020, the first record of Wolffia arrhiza was made in Novosibirsk region (Western Siberia) in a floodplain lake. Wolffia arrhiza formed vast stands with an area of hundreds of square meters and with high productivity. Besides monodominant communities, it was met as a component of the cenoses of such hydrophytes as Stratiotes aloides and Hydrocharis morsus-ranae, as well as of the helophyte communities formed by Typha latifolia and Eleocharis mamillata. According to local residents, Wolffia was observed as abundant for some years; thus, most likely, the population winters safely at the latitude of Novosibirsk. The most likely source of Wolffia arrhiza appearance in the lake was an accidental introduction from an aquarium, although the possibility of this plant entering the lake in high-water years from the wastewater of the municipal settling tank of Novosibirsk sewage waters also exists.

Duckweeds represent a small, free-floating aquatic family (Lemnaceae) of the monocot order Alismatales with the fastest growth rate among flowering plants. They comprise five genera (Spirodela, Landoltia, Lemna, Wolffiella, and Wolffia) varying in genome size and chromosome number. Spirodela polyrhiza had the first sequenced duckweed genome. Cytogenetic maps are available for both species of the genus Spirodela (S. polyrhiza and S. intermedia). However, elucidation of chromosome homeology and evolutionary chromosome rearrangements by cross-FISH using Spirodela BAC probes to species of other duckweed genera has not been successful so far. We investigated the potential of chromosome-specific oligo-FISH probes to address these topics. We designed oligo-FISH probes specific for one S. intermedia and one S. polyrhiza chromosome (Fig. 1a). Our results show that these oligo-probes cross-hybridize with the homeologous regions of the other congeneric species, but are not suitable to uncover chromosomal homeology across duckweeds genera. This is most likely due to too low sequence similarity between the investigated genera and/or too low probe density on the target genomes. Finally, we suggest genus-specific design of oligo-probes to elucidate chromosome evolution across duckweed genera.

The free-floating aquatic duckweeds consist of the five genera, Spirodela , Landoltia , Lemna , Wolffiella and Wolffia , comprising 36 species within the monocot order of Alismatales. They are strongly adaptable to various environments and are widely distributed in a variety of climates all over the world except that Wolffiella species are restricted to the Americas and Africa. Among them, Spirodela species have large a flattened frond with 5−11 rhizoids while the rootless Wolffia species form an oval-shaped frond and are the smallest flowering plants. Duckweeds seldom flower and their rapid asexual propagation allows them to accumulate biomass quickly. They usually bud new generations (daughter fronds) from their reproductive pouches at the base of the mother fronds and the frond number almost doubles within 24 h under good growth conditions yielding the fastest-growing flowering plants. They tend to be associated with nutrient-rich or eutrophic freshwater environments with slow-moving flow such as ponds, lakes, ditches, and paddy fields. While duckweeds become more reduced from Spirodela to Wolffia , their genome size varies 13-fold, ranging from 150 Mb in Spirodela polyrhiza to 1881 Mb in Wolffia arrhiza . With the development of long-read sequencing technology, the genomes of common duckweed species including S. polyrhiza , Lemna minor , Lemna gibba and Wolffia australiana have been sequenced and assembled. The underlying molecular mechanisms and regulatory networks in duckweeds under different treatments such as starvation, salt stress, heavy metal and radiation have also been revealed by transcriptome, proteome and metabolome analyses for the genera Spirodela , Landoltia , and Lemna enhancing their potential applications in the fields of phytoremediation and bioenergy. Furthermore, genetic transformation systems for some common duckweeds such as L. minor , Lemna aequinoctialis , S. polyrhiza and Wolffia globosa have been established, and especially the frond transformation systems have significantly improved transformation efficiencies (more than 90%). These characteristics have made duckweeds model systems for several decades for the study of plant physiology, biochemistry, ecotoxicology, and have contributed to knowledge of auxin biosynthesis, plant flowering and the circadian system. Duckweeds have also been widely used for the treatment of agricultural, municipal, and even industrial wastewater because they can uptake nitrogen and phosphorus as well as quickly accumulate heavy metals and organic pollutants. Besides, their accumulated biomass is rich in starch and protein and therefore can be used for feed applications and biofuels. In this review, we introduce the origin, classification and evolution of duckweeds, as well as research in morphology and anatomy, physiology, genetic transformation and omics studies. We further discuss the application of duckweeds in food, feed, bioenergy, and bioremediation. Finally, we highlight the challenges and future directions of duckweed research, providing a reference for basic biological research and resource utilization.

Wolffia is a genus of protein-rich aquatic plants. Mankai, a cultivated strain of Wolffia globosa, contains more than 40 % protein based on dry matter evaluation. Furthermore, Mankai is nutritionally excellent as a food material, and is expected to be applicable to various products as a substitute for animal protein. A battery of toxicological studies was conducted on the dried product of Mankai (Dry Mankai), with the expectation to utilize it as a raw material for food applications. Dry Mankai was not genotoxic in a bacterial reverse mutation test and in vitro micronucleus assay. In the subchronic toxicity study, rats were provided Dry Mankai in the diet at levels of 0 %, 5 %, 10 %, or 20 % (w/w), equivalent to 0, 3.18, 6.49, and 13.16 g/kg/day for males and 0, 3.58, 7.42, and 15.03 g/kg/day for females, respectively. No adverse effects that could be attributable to treatment were observed in clinical observations, body weight, food consumption, ophthalmology, hematology and blood chemistry, urinalysis, and macroscopic and microscopic findings. According to the repeated-dose study in rats, the no observed adverse effect level of Dry Mankai was 20 % (w/w) for both sexes (13.16 and 15.03 g/kg/day for males and females, respectively).

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on the safety of water lentil powder as a novel food (NF) pursuant to Regulation (EU) 2015/2283. Water lentils refer to aquatic plants belonging to the Araceae family and represented by five genera (Lemna, Wolffia, Wolffiella, Landoltia and Spirodela). The NF is thermally washed and dried water lentils, which are produced as a polyculture crop consisting of species from the Lemna genus (70-100%) and the Wolffia genus (0-30%). The main constituents of the NF are protein, fibre and fat. The Panel notes that the concentration of trace elements and contaminants in the NF is highly dependent on the conditions of cultivation of the plant and the fertiliser composition. The NF is expected to be stable and to comply with the specifications during the suggested shelf life. The NF is intended for human consumption as a food ingredient in herbs, spices and seasonings, sauces, soups and broths, protein products, dietary food for weight control and as a food supplement. The target population is the general population, except for food supplements which are exclusively intended for consumption by adults. The Panel considers that based on the composition of the NF and the proposed intended uses, the NF is not nutritionally disadvantageous, except for the concerns regarding intake of manganese from the NF. No adverse effect was observed in the submitted 90-day subchronic study, at the highest dose, 1,000 mg/kg body weight (bw) per day of NF. The Panel considers that, based on the protein concentration, the consumption of the NF may trigger allergic reactions. The Panel concluded that an increase in manganese intake from the NF used as food ingredient or food supplements is of safety concern and the safety of the NF cannot be established. (C) 2021 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.

The production of recombinant proteins in transgenic plants is becoming an increasingly serious alternative to classical biopharming methods as knowledge about this process grows. Wolffia arrhiza, an aquatic plant unique in its anatomy, is a promising expression system that can grow in submerged culture in bioreactors. In our study 8550 explants were subjected to Agrobacterium-mediated transformation, and 41 independent hygromycin-resistant Wolffia lines were obtained, with the transformation efficiency of 0.48%. 40 of them contained the hirudin-1 gene (codon-optimized for expression in plants) and were independent lines of nuclear-transformed Wolffia, the transgenic insertion has been confirmed by PCR and Southern blot analysis. We have analyzed the accumulation of the target protein and its expression has been proven in three transgenic lines. The maximum accumulation of recombinant hirudin was 0.02% of the total soluble protein, which corresponds to 775.5 ± 111.9 ng g(−1) of fresh weight of the plant. The results will be used in research on the development of an expression system based on Wolffia plants for the production of hirudin and other recombinant pharmaceutical proteins.

A 40 days feeding trial with Labeo rohita (rohu) fry was conducted in six outdoor cemented tanks (5m × 4m × 1 m; 6–8 cm soil base) to establish the relative impact of on‐farm grown live Wolffia globosa (a duckweed with crude protein of 28.57%) and a formulated iso‐nitrogenous feed (crude protein 28.37%) on growth performance, survival, health and overall quality of fingerlings. The experimental tanks were dried, limed at 250 kg/ha, filled with ground water and subsequently applied with cow dung (soaked overnight) and mustard oil cake at 1,000 kg/ha and 50 kg/ha respectively. The fry were stocked at 0.3 millions/ha in six prepared tanks, and fed live Wolffia (T1) and formulated feed (T2). Results of the study indicate better performance (p

Plants in the family Lemnaceae are aquatic monocots and the smallest, simplest, and fastest growing angiosperms. Their small size, the smallest family member is 0.5 mm and the largest is 2.0 cm, as well as their diverse morphologies make these plants ideal for laboratory studies. Their rapid growth rate is partially due to the family’s neotenous lifestyle, where instead of maturing and producing flowers, the plants remain in a juvenile state and continuously bud asexually. Maturation and flowering in the wild are rare in most family members. To promote further research on these unique plants, we have optimized laboratory flowering protocols for 3 of the 5 genera: Spirodela, Lemna, and Wolffia in the Lemnaceae. Duckweeds were widely used in the past for research on flowering, hormone and amino acid biosynthesis, the photosynthetic apparatus, and phytoremediation due to their aqueous lifestyle and ease of aseptic culture. There is a recent renaissance in interest in growing these plants as non-lignified biomass sources for fuel production, and as a resource-efficient complete protein source. The genome sequences of several Lemnaceae family members have become available, providing a foundation for genetic improvement of these plants as crops. The protocols for maximizing flowering described herein are based on screens testing daylength, a variety of media, supplementation with salicylic acid or ethylenediamine-N,N′-bis(2-hydroxyphenylacetic acid) (EDDHA), as well as various culture vessels for effects on flowering of verified Lemnaceae strains available from the Rutgers Duckweed Stock Cooperative.

Watermeal, Wolffia australiana, is the smallest known flowering monocot and is rich in protein. Despite its great potential as a biotech crop, basic research on Wolffia is in its infancy. Here, we generated the reference genome of a species of watermeal, W. australiana, and identified the genome-wide features that may contribute to its atypical anatomy and physiology, including the absence of roots, adaxial stomata development, and anaerobic life as a turion. In addition, we found evidence of extensive genome rearrangements that may underpin the specialized aquatic lifestyle of watermeal. Analysis of the gene inventory of this intriguing species helps explain the distinct characteristics of W. australiana and its unique evolutionary trajectory., Halim Park and Jin Hwa Park et al. report the nuclear genome sequence of the duckweed Wolffia australiana, the smallest known flowering plant. The genome assembly represents an improvement over a recently published genome and highlights genome rearrangements that may be linked to its specialized aquatic adaptations.

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on the safety of water lentil powder as a novel food (NF) pursuant to Regulation (EU) 2015/2283. Water lentils refer to aquatic plants belonging to the Araceae family and represented by five genera (Lemna, Wolffia, Wolffiella, Landoltia and Spirodela). The NF is thermally washed and dried water lentils, which are produced as a polyculture crop consisting of species from the Lemna genus (70-100%) and the Wolffia genus (0-30%). The main constituents of the NF are protein, fibre and fat. The Panel notes that the concentration of trace elements and contaminants in the NF is highly dependent on the conditions of cultivation of the plant and the fertiliser composition. The NF is expected to be stable and to comply with the specifications during the suggested shelf life. The NF is intended for human consumption as a food ingredient in herbs, spices and seasonings, sauces, soups and broths, protein products, dietary food for weight control and as a food supplement. The target population is the general population, except for food supplements which are exclusively intended for consumption by adults. The Panel considers that based on the composition of the NF and the proposed intended uses, the NF is not nutritionally disadvantageous, except for the concerns regarding intake of manganese from the NF. No adverse effect was observed in the submitted 90-day subchronic study, at the highest dose, 1,000 mg/kg body weight (bw) per day of NF. The Panel considers that, based on the protein concentration, the consumption of the NF may trigger allergic reactions. The Panel concluded that an increase in manganese intake from the NF used as food ingredient or food supplements is of safety concern and the safety of the NF cannot be established.

To colonise other planets, self-sufficiency of space missions is mandatory. To date, the most promising technology to support long-duration missions is the bioregenerative life support system (BLSS), in which plants as autotrophs play a crucial role in recycling wastes and producing food and oxygen. We reviewed the scientific literature on duckweed (Lemnaceae) and reported available information on plant biological traits, nutritional features, biomass production, and space applications, especially of the genus Wolffia. Results confirmed that the smallest existing higher plants are the best candidate for space BLSS. We discussed needs for further research before criticalities to be addressed to finalise the adoption of Wolffia species for space missions.

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on the safety of water lentil powder as a novel food (NF) pursuant to Regulation (EU) 2015/2283. Water lentils refer to aquatic plants belonging to the Araceae family and represented by five genera (Lemna, Wolffia, Wolffiella, Landoltia and Spirodela). The NF is thermally washed and dried water lentils, which are produced as a polyculture crop consisting of species from the Lemna genus (70-100%) and the Wolffia genus (0-30%). The main constituents of the NF are protein, fibre and fat. The Panel notes that the concentration of trace elements and contaminants in the NF is highly dependent on the conditions of cultivation of the plant and the fertiliser composition. The NF is expected to be stable and to comply with the specifications during the suggested shelf life. The NF is intended for human consumption as a food ingredient in herbs, spices and seasonings, sauces, soups and broths, protein products, dietary food for weight control and as a food supplement. The target population is the general population, except for food supplements which are exclusively intended for consumption by adults. The Panel considers that based on the composition of the NF and the proposed intended uses, the NF is not nutritionally disadvantageous, except for the concerns regarding intake of manganese from the NF. No adverse effect was observed in the submitted 90-day subchronic study, at the highest dose, 1,000 mg/kg body weight (bw) per day of NF. The Panel considers that, based on the protein concentration, the consumption of the NF may trigger allergic reactions. The Panel concluded that an increase in manganese intake from the NF used as food ingredient or food supplements is of safety concern and the safety of the NF cannot be established. (C) 2021 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.

Vibriosis is a commonly found bacterial disease identified among fish and shellfish cultured in saline waters. A multitude of Vibrio species have been identified as the causative agents. LamB, a member of outer membrane protein (OMPs) family of these bacteria is conserved among all Vibrio species and has been identified as an efficient vaccine candidate against vibriosis. Rootless duckweed (Wolffia) is a tiny, edible aquatic plant possessing characteristics suitable for the utilization as a bioreactor. Thus, we attempted to express a protective edible vaccine antigen against fish vibriosis in nuclear-transformed Wolffia. We amplified LamB gene from virulent Vibrio alginolyticus and it was modified to maximize the protein expression level and translocate the protein to the endoplasmic reticulum (ER) in plants. It was cloned into binary vector pMYC under the control of CaMV 35S promoter and introduced into Wolffia globosa by Agrobacterium-mediated transformation. Integration and expression of the LamB gene was confirmed by genomic PCR and RT-PCR. Western blot analysis revealed accumulation of the LamB protein in 8 transgenic lines. The cross-protective property of transgenic Wolffia was evaluated by orally vaccinating zebrafish through feeding fresh transgenic Wolffia and subsequently challenging with virulent V. alginolyticus. High relative percent survival (RPS) of the vaccinated fish (63.3%) confirmed that fish immunized with transgenic Wolffia were well-protected from Vibrio infection. These findings suggest that Wolffia expressed LamB could serve as an edible plant-based candidate vaccine model for fish vibriosis and feasibility of utilizing Wolffia as bioreactor to produce edible vaccines.

Wolffia is the fastest growing plant genus on Earth with a recorded doubling time of less than a day. Wolffia has a dramatically reduced body plan, primarily growing through a continuous, budding-type asexual reproduction with no obvious phase transition. Most plants are bound by the 24-hour light-dark cycle with the majority of processes such as gene expression partitioned or phased to a specific time-of-day (TOD). However, the role that TOD information and the circadian clock plays in facilitating the growth of a fast-growing plant is unknown. Here we generated draft reference genomes for Wolffia australiana (Benth.) Hartog & Plas to monitor gene expression over a two-day time course under light-dark cycles. Wolffia australiana has the smallest genome size in the genus at 357 Mb and has a dramatically reduced gene set at 15,312 with a specific loss of root (WOX5), vascular (CASP), circadian (TOC1), and light-signaling (NPH3) genes. Remarkably, it has also lost all but one of the NLR genes that are known to be involved in innate immunity. In addition, only 13% of its genes cycle, which is far less than in other plants, with an overrepresentation of genes associated with carbon processing and chloroplast-related functions. Despite having a focused set of cycling genes, TOD cis-elements are conserved in W. australiana, consistent with the overall conservation of transcriptional networks. In contrast to the model plants Arabidopsis thaliana and Oryza sativa, the reduction in cycling genes correlates with fewer pathways under TOD control in Wolffia, which could reflect a release of functional gating. Since TOD networks and the circadian clock work to gate activities to specific times of day, this minimization of regulation may enable Wolffia to grow continuously with optimal economy. Wolffia is an ideal model to study the transcriptional control of growth and the findings presented here could serve as a template for plant improvement.

The Lemnaceae family, commonly called duckweeds, is 37 species of the smallest and simplest flowering plants found floating on nutrient-rich waters worldwide. Their small size and rapid clonal growth in aseptic conditions made them a stable and simple model for plant research especially from 1950 to 1990, when they were used to study plant physiology and biochemistry including auxin synthesis and sulfur metabolism. Duckweed research then saw a resurgence in 2008 when global fuel prices rose and the US Department of Energy funded the sequencing of the Spirodela polyrhiza genome. This launched not only the genomic investigations detailed in this book, but the regrowth of duckweed industrial applications. Thanks to their ability to quickly absorb nitrogen, phosphorous, and other nutrients while removing pathogens and growing at a rate of 13–38 dry tons/hectare year in water treatment lagoons, scientists are currently exploring ways that duckweed can convert agricultural and municipal wastewater into clean water and a high-protein animal feed. The potential of these plants for phytoremediation of heavy metals and organic compounds also allows the possibility to clean the wastewater from heavy industry while providing biofuels and even plastics. Finally, thanks to their superb nutritional profile Wolffia species grown in clean conditions promise to become one of the healthiest and most environmentally friendly vegetables. Given the importance of these incredible plants, it is no wonder researchers are investigating the genetic mechanisms that make it all possible.

There are five genera (Spirodela, Landoltia, Lemna, Wolffiella and Wolffia) of duckweed species widely distributed in various freshwater habitats worldwide. Rapid growth rate, predominantly asexual reproduction and floating growth made them ideal for a plant model. The sensitivity to some toxicants and enrichment capacity also made duckweeds favorable in biomonitoring and bioremediation in contaminated water. Furthermore, duckweeds have increasingly been considered as alternative sources for bioenergy and food, due to their high biomass accumulation rate and nutritional contents. Both stable and transient transformation protocols have been established for some duckweed species. Agrobacterium-mediated method is the main approach in duckweeds genetic transformation, which could be affected by the type of explants, Agrobacterium strains, their densities, co-culture conditions and antibiotics and their concentrations. Particle treatment and other improvements such as vacuum infiltration can accelerate transient transformation efficiency by microprojectile bombardment method. Inadequacies are still present in genetic transformation of some duckweed species including low efficiency of transformation and long-time period especially using calli as infected materials. Therefore, more concentrated and persistent efforts to develop efficient approaches for genetic transformation of duckweeds are still needed. Furthermore, it is necessary to make an effort to express various types of genes so as to expand the development and utilization of duckweeds.

Duckweeds (family Lemnaceae) comprise 37 angiosperm species, which are distributed among five genera. Although these tiny specimens represent the smallest flowering plants on earth, the group is practically ubiquitous in water bodies worldwide. The paucity of morphological features in duckweeds has made it difficult to elucidate their evolutionary history, or to present a compelling classification of the group, but more recent molecular evidence has facilitated an improved systematic evaluation of these unique plants. The duckweeds are closely related to aroids (family Araceae), with which they share several morphological features. Within Lemnaceae, the two species of Spirodela and the monotypic genus Landoltia are more distantly related to other duckweeds than are the larger genera Lemna, Wolffia, and Wolffiella to one another. A substantial amount of plastid DNA sequence data has upheld a phylogeny for the family that is mostly consistent, and many of those relationships have been corroborated by the recent addition of nuclear DNA data. Morphologically, the genera lacking roots (Wolffia and Wolffiella) comprise a single lineage, as do the three largest genera (Lemna, Wolffia, and Wolffiella) that are more reduced in comparison with Landoltia and Spirodela. The biogeography of Lemnaceae indicates that numerous dispersal events have occurred in relatively recent evolutionary time, and that several species essentially are cosmopolitan. Although not particularly speciose, duckweeds comprise a surprisingly diverse group with much potential for exploring various genetic, biochemical, and metabolic phenomena.

Duckweed is an interesting model for studying cytogenetics, epigenetics and karyotype evolution. Belonging to the monocotyledonous arum or aroid family Araceae, these aquatic plants present an approximately 12-fold range of different genome sizes, from 158 Mbp (Spirodela sps.) to 1881 Mbp (Wolffia arrhiza) and variable chromosome numbers. In addition to reduced gene repertoires that found in so far all published duckweed genomes of Spirodela, Lemna and Wolffia species, several peculiar genome and epigenome features (e.g. the lowest copy number of genes coding for rRNA, extreme levels of global DNA methylation, and atypical patterns of heterochromatic and euchromatic territories) indicate a unique and interesting history of duckweed genome evolution, organization and adaptation to plants with simplified body architecture and extremely fast growth rate. Together with the high-throughput long-read, long-range information and optical mapping technologies, available cytogenetic resources, including an efficient and robust protocol of multicolour fluorescence in situ hybridization (mcFISH) and mitotic chromosome preparation, and a Spirodela genome-integrated bacterial-artificial-chromosome (BAC) map with ancestral chromosome linkages allow further comprehensive comparative genomic and cytogenetic analysis between duckweed, its close relatives, and other monocotyledonous plants of interest.

Duckweeds are the simplest and smallest (“frond” size 1 mm to less than 1 cm) flowering plants, able to grow on fresh and polluted water. In the recent past, intense research to understand various species and their potential has been underway, especially in the genetics and biochemical repertoire. Duckweeds come under the family Lemnaceae and contain genera such as Lemna, Spirodela, Landolita, Wolffia and Wolffella. Duckweeds thrive ubiquitously as autotrophs using photosynthesis to source their nutritional requirements from solar energy and minerals from the rhizosphere. They are also endowed to absorb and accumulate heavy metals, radionucleotides and metalloids with potential for phytoremediation. The metabolic versatility of duckweeds can be deployed as nutrition in aquaculture, livestock and of late as functional foods. Duckweeds are currently being explored to find new applications in feed to complement diets and increase animal growth either alone or coupled with crop residues to bring about a balance of nutrients. Duckweeds have emerged as an important food resource; a case in point is Wolffia arrhiza. Consumed in various formats, duckweeds have a good balance of proteins, fat, starch, an array of favorable amino acids and fatty acids, minerals and antioxidants, phytosterols and much sought after omega-3 fatty acids as well.

Duckweeds include the world's smallest and fastest growing flowering plants that have the capacity to produce huge biomass with a broad range of potential applications like production of feed and food, biofuel and biogas. In order to achieve optimal and sustainable commercial system, it is necessary that suitable species and clones of duckweeds be identified and selected based on appropriate strategies. However, a high degree of reduction in their structural complexity poses serious problems in identification of closely related species of duckweeds, on a morphological basis. Use of molecular taxonomic tools is the present solution. The state of the art of molecular taxonomy of all the five genera of duckweeds (Spirodela, Landoltia, Lemna, Wolffiella, and Wolffia) is based mainly on the techniques of fingerprinting by amplified fragment length polymorphism (AFLP) and barcoding using sequences of plastidic DNA fragments. After more than 15 years of molecular taxonomic investigations, a certain viewpoint is now available demonstrating all five genera to be monophyletic. Also, the phenetic analyses had made huge progress in delineating the currently defined 36 species of duckweeds, although, all species cannot yet be defined with confidence. Wolffiella has turned out to be the most complicated genus as only 6 to 7 species out of the 10 can be reliably delineated. Further progress in the phylogenetic and phenetic analyses requires more advanced methods like next generation and/or whole genome sequencing. First results using the method genotyping-by-sequencing in the genus Lemna (in combination with metabolomic profiling by matrix-assisted laser desorption ionization time-of-flight mass-spectrometry (MALDI-TOF-MS) as well as AFLP and barcoding by plastidic sequences) are more promising: The species Lemna valdiviana and Lemna yungensis were united to one species, Lemna valdiviana. This reduced the total number of Lemnaceae species to 36.