NUCLEAR GENOME CHARACTERIZATION OF THE CARRAGEENOPHYTE AGARDHIELLA-SUBULATA (RHODOPHYTA)

DNA reassociation kinetics were used to determine nuclear genome organization and complexity in Agardhiella subulata (Gigartinales, Rhodophyta). Results indicate the presence of three second-order components corresponding to fast (22%), intermediate (68%) and slow (10%) fractions. Thus, the genome consists of 90% repetitive sequences. Microspectrophotometry with the DNA-localizing fluorochrome DAPI was used to confirm ploidy level differences in the gametophytic and tetrasporophytic phases. Results indicate that meiosis occurs during tetrasporogenesis. Comparison of mean nuclear DNA (I(f)) values to chicken erythrocytes (RBC) resulted in an estimate of 0.9 pg/2C genome for Agardhiella. Karyological studies using aceto-orcein revealed a chromosome complement of 2N = 44 in carposporangia and the presence of 22 bivalents during diakinesis of tetraspore mother cells.