Molecular identification of Azolla in the Yangtze River Watershed, China

Abstract

Seven samples were collected broadly from the Yangtze River watershed of China during a search for Azolla pinnata asiatica, intended as molecular references to identify the subspecies of a new exotic congener in Florida. Molecular taxonomic analysis was carried out using chloroplast trnG-trnR and trnL-trnF, in addition to nuclear ITS1 sequences, which when referenced against NCBI yielded the unexpected result of Azolla caroliniana for all seven samples. In four of five provinces sampled, cold-tolerant A. filiculoides and A. caroliniana would be expected to outcompete A. pinnata due to biological advantages during over-wintering and early spring growth. However, A. caroliniana’s predominance over A. filiculoides in this limited sampling taken widely from the Yangtze watershed was unexpected given the historical predominance of Azolla filiculoides introduction in the literature. The explanation may be A. caroliniana’s use in early rice systems, its intermediate tolerance to heat and cold, and its high biomass production. Azolla caroliniana’s hybrid status is further characterized here using NCBI ITS1 Blasts of an SLA Illumina 2000 dataset.