Male sterility and ecology of Dutch Origanum vulgare populations

Male sterility was investigated in 19 Dutch Origanum vulgare populations by counting stamens and relating the numbers to several environmental factors. A mean of 11.5% male sterility was found for all populations, while 12 populations had a low value of 0-4.5% and the other 7 a higher one of 8.9-64.2%. Of the 53 plants counted 43% showed no staminal reduction and 57% a reduction of0.2-100%. Only 2 plants were found with a 100% reduction, which is e. 4%. Considerable variation in male sterility was established for individual plants within one population and also, rather frequently, for different stems on one plant. Of 4384 flowers counted 9.5% had no stamens, while 1.3% had I, 1.5% had 2 and 1.0% had 3 well developed stamens. The remaining 86.7% had all 4 stamens well developed. It was found that populations growing in relatively undisturbed Mesobromion/Trifolion vegetation possessed low male sterility values, and that populations in disturbed Arrhenatherion/ Lolio-Potentillion vegetation often had much higher male sterility percentages. Further it was ascertained that small, isolated populations usually had a much higher male sterility than compact populations. No correlations could be found between male sterility and the following environmental factors; acidity, calcium, phosphorus, organic matter, sand, clay, gradient and aspect.