Stomatal frequency and size differentiate ploidy levels in Aegilops neglecta

Aegilops neglecta Req. ex Bertol. is a forage goatgrass that has tetraploid and hexaploid forms. No morphological trait is known to distinguish between the two forms. Accessions of Ae. neglecta representing diverse germplasm were characterized for stomatal frequency and size on the adaxial surface of leaves. Stomatal frequency among tillers within a plant and among leaves on a tiller was measured. Significant variation was found in stomatal frequency between the ploidy levels for basal leaves 2 and 3 and the penultimate and flag leaves. Mean stomatal frequency for basal leaves ranged from 50.24 to 54.80 per mm(2) for tetraploid and from 39.24 to 40.50 per mm(2) for hexaploid accessions. For upper leaves, it varied from 52.88 to 53.50 per mm(2) for tetraploid and from 46.12 to 46.40 per mm(2) for hexaploid accessions. The two ploidy forms also exhibited clear differences for stomatal size on the basal and upper leaves of the main tiller. Mean stomatal size for the basal leaves ranged from 41.42 to 46.09 mum for tetraploid and from 53.59 to 54.97 mum for hexaploid accessions. For upper leaves, stomatal size varied from 47.29 to 53.29 mum in tetraploid and from 64.76 to 66.84 mum for hexaploid accessions. None of the individual accession ranges overlapped between the ploidy levels. Stomatal frequency and size were highly negatively correlated. Increased ploidy in Ae. neglecta has resulted in fewer but larger stomata per unit leaf area. Stomatal size and/or frequency on the adaxial surface of leaves could be used to distinguish tetraploid from hexaploid cytotypes in Ae. neglecta in fresh material from Turkey collected in the field.