Morphological and Molecular Characterization of Azolla Accessions in Kenya

Abstract

Background. Azolla Lam., a mosquito fern, is invasive in major rice growing Schemes in Kenya, where it clogs irrigation canals and forms dense mats in paddy fields. However, the species of Azolla has not been established. Objective. to characterize Azolla accessions collected from six major rice Irrigation Schemes in Kenya: Mwea, Ahero, West Kano, Bunyala, Taveta and TARDA. Methodology. Azolla accessions were collected, grown for 10 days at Mwea Irrigation Agricultural Development Centre (MIAD) and their vegetative traits examined microscopically using 13 Pereira’s morphological characters. The vegetative characteristics were evaluated on a binary 0/1 system, pairwise similarity was estimated using Jaccard’s coefficient (S1) and a dendrogram generated. Genomic DNA was extracted from each of the accessions, amplified with SCAR primers and amplified products resolved and scored using agarose gels. Polymorphic SCAR markers were identified and correlated to the accessions. Results. Nine vegetative characters useful for distinguishing between the two Azolla sub-genera (Euazolla and Rhizosperma) and the seven Azolla species were examined. Possession of hook-like, septate glochidia suggested the presence of Azolla filiculoides in TARDA1 accession. The presence of pinnate sporophyte with septate rhizome papillae and fronts measuring 2-4 cm with 2-4 cm long roots and lack of anthocyanin suggested the presence of Azolla nilotica for TARDA 2 and Taveta 2 accessions. SCAR marker based 490 bp primers that identify with A. filiculoides also amplified Mwea and Taveta 1 accessions to give a distinct band. Implications. Results suggest the existence of Azolla nilotica and Azolla filiculoides among the Kenyan accessions. Conclusion. Azolla filiculoides and Azolla nilotica are the two main Azolla species characterized in the major Irrigation Schemes in Kenya. Of the two species, Azolla filiculoides has infested four of the Kenya irrigation schemes (Mwea, Ahero, Bunyala, Tana River and West Kano), while Azolla nilotica exists only in Taveta and TARDA.