Weigela (Thunb.) improvement by mutagenesis: looking for a method

When three years old shrubs of Weigela (Thunb.) are severely pruned, the collar zone produces large populations of shoots at the same stage of development. Previously irradiated with gamma rays of 60Co, this collar zone will produce a large population of cuttings, easy and cheap to grow, amoung which screening for mutant will be more efficient. A factorial experimental design has been used with the following combinations: - Pot-plants maintained outdoor compared with pot-plants introduced in the greenhouse a week before irradiation. Keeping existing buds on the branches, compared with suppression of any visible bud. Doses 0.4 and 6 kR given at a dose rate of 1 kRh-1. Few plants, out of the design, have been treated to 7 kR