Ploidy determination of black wattle (Acacia mearnsii) using stomatal chloroplast counts

Synopsis The arrangements of chloroplasts and numbers within the stoma were examined as a rapid indirect technique for the identification ofploidy level in blackwattle (Acacia mearnsii de Wild). Chloroplast counts were made from stomatal guard cells from leaves of known diploid (2n=2x=26) and tetraploid (2n=4x=52) plants grown under nursery conditions. Three-month-old plant material was used and five plants were chosen at random across six lines (3 diploids, 3 tetraploids). For diploids the mean number ofchloroplasts per stoma was 9,89 ± 0,170 and 22,75 ± 0,170 for tetraploids. Chloroplasts in diploid guard cells were polarized into the corners, while evenly distributed in the tetraploids. These differences noted between the ploidy levels were significant (P<0,01). The analysis of stomatal chloroplast number and arrangement have proven to be an accurate indirect technique to distinguish between diploid and tetraploid black wattle.