MORPHOLOGICAL AND MOLECULAR CHARACTERIZATION OF DUCKWEED (LEMNACEAE) IN SELECTED WETLANDS AND POND WATERS OF THARAKA- NITHI COUNTY, KENYA

Abstract

Duckweeds are aquatic herbs adapted to various geographic and climatic zones, with significant applications in wastewater treatment, animal feeds, biofuel production, and as a culinary ingredient in some Asian countries. In Kenya, including Tharaka-Nithi County, duckweed has attracted the attention of farmers as a feed supplement for livestock. However, commercial extraction poses a threat to the survival of the plant and its ecological roles, necessitating its conservation and promotion of sustainable utilization. This study aimed at characterizing local duckweed species to understand their taxonomic variation and distribution in Tharaka-Nithi County. Samples were collected from selected wetlands and ponds, with GPS coordinates and elevation of sampling points recorded for analysis of their distribution. Morphological features of duckweed were studied and the DNA extracted for molecular characterization using DNA barcoding markers. One hundred and forty-four samples of duckweed were collected and from morphological characterization, they were grouped into nine clones. All the nine clones had parallel veins and obovate fronds with rounded apices. Morphological features such as frond symmetry, color, border and length varied among clones. Hence, frond symmetry, border and color, formed significant qualitative characteristics while frond length formed a significant quantitative characteristic. Morphological data suggested that the clones belonged to the same genus, consistent with previous studies. Further, molecular characterization that was done using RBCL and matK genes, successfully confirmed they were duckweed species. Six RBCL gene amplification products were sequenced, and BLAST search results indicated they were from the genus Lemna. Three samples collected from Chogoria, Gatithini and Ikumbo were identified as Lemna minor. In contrast, samples collected from Marimanti, Kathwana and Kaanwa were identified as Lemna turionifera, Lemna aequinoctialis, and Lemma perpusilla respectively. Lemna minor and Lemna turionifera were predominant in treated sewage ponds while Lemna aequinoctialis and Lemma perpusilla were found on still waters in swamps and fishponds respectively. This study provides information that can be used in formulating conservation and utilization policies for duckweed in Tharaka-Nithi County and beyond. The findings highlight the need for molecular identification to supplement morphological methods due to the intricate nature of duckweed species identification. Through this foundational understanding of duckweed biodiversity in the region, this research contributes valuable insights into sustainable resource management and conservation strategies, ensuring the long-term viability of these vital aquatic plants in local ecosystems.