Morphological variation, chromosome number, and DNA barcoding of Giant Duckweed (Spirodela polyrhiza) in Vietnam

Abstract

Our present study is the first systematic survey on duckweed biodiversity in Vietnam. More than 100 samples of Spirodela, Lemna, and Wolffia were collected throughout Vietnam and maintained under laboratory conditions. In this report, the morphological variation, chromosome number, and DNA barcoding on Spirodela samples were investigated.  S. polyrhiza and S. intermedia are the only two species of Spirodela genus - the most ancient genus among the five duckweed genera. The obtained DNA sequences of atpF- atpH and psbK – psbI regions showed that all 29 Spirodela samples collected from different regions along Vietnam are S. polyrhiza. Specific SNPs of individual S. polyrhiza clones were identified in the psbK-psbI region. The differences in genome size (163 – 170 Mbp), frond size (0.80 – 1.25 cm2), frond shape (oval/circular symmetry/asymmetry), stomata (20.57 – 24.00 µm in length and 10.00 – 21.30 µm in width) and root number (4.75 – 6.69 roots) among six representatives S. polyrhiza clones were recorded. The chromosome number of these clones was uniformly 2n=40.