AN IMPROVED METHOD INVOLVING HYDROPONIC CULTURE FOR THE PRODUCTION OF SEXUAL HYBRIDS BETWEEN DIHAPLOID SOLANUM-TUBEROSUM AND DIPLOID SOLANUM-MICRODONTUM

Dihaploid Solanum tuberosum and diploid S. microdontum plants were grown in soil and hydroponics under glasshouse and growth room conditions. A high light intensity was necessary for flower induction in both species and the dihaploid flowered only when grown in hydroponics. Premature berry abscission was retarded by tuber removal and prevented by the addition of indole acetic acid to the nutrient solution. Seeds from prematurely abscised berries germinated poorly in soil, but germinated almost as well as those seeds from indole acetic acid-treated plants when placed on Murashige and Skoog (1962) based culture medium. The hybrid plants were intermediate in morphology, compared to the parents, possessed heterotic vigour and were male fertile. Germinating hybrid seeds on a colchicine-containing medium led to poorly growing plants with ploidy chimeras. Hybrid plant ploidy levels were doubled by regenerating plants from stem/leaf explants on the tuber disc regeneration medium of Jarret et al. (1980).