Development of Seedless Grapefruit Cultivars through Budwood Irradiation

Buds from a mature ‘Foster’ grapefruit ( Citrus paradisi Macf.) tree were exposed to 3, 5, 7, 9, and 11 kilorad (kr) of gamma irradiation. The irradiated buds were grafted to rootstocks in the nursery and greenhouse. The LD 50 was near 5 kr for buds grafted in the greenhouse and 9 kr for those in the nursery; however, no buds receiving more than 5 kr initiated growth. Grafted trees that grew were field grown until fruiting and seed per fruit was counted. Several nonjuvenile, commercially seedless clones were developed among small populations of plants, and in significantly less time than required through seed irradiation.