Genotypic specificity of walnut (Juglans regia L.) pollen germination on different germination media

Abstract The pollen of three walnut cultivars ('Geisenheim 139', 'Geisenheim 251' and 'Elit') was germinated on the culture media designed by combining different concentrations of agar (0.6 and 0.8%), sucrose (10, 15 and 20%), boric acid (0, 300 and 600 ppm) and calcium chloride (0, 50 and 100 ppm). A total of 54 combinations of these substances for each of the cultivars were tested in order to develop the most suitable medium for in vitro pollen germination tests in walnut. Walnut pollen germination was significantly affected by genotype and agar, sucrose, boric acid and calcium chloride concentrations in the medium. The average pollen germination percentage was the highest (13.4%) in cv. 'Geisenheim 251' and the lowest (6.8%) in cv. 'Geisenheim 139'. Significant interactions were observed between the germination medium components, as well as between cultivars and germination medium. The optimum germination medium for 'Geisenheim 139' pollen contained 0.6% agar, 20% sucrose, 600 ppm boric acid and 0% calcium chloride. The pollen of cvs. 'Elit' and 'Geisenheim 251' gave maximum germination on the medium containing 0.6% agar, 15% sucrose, 300 ppm boric acid and 50 ppm calcium chloride.