In vitro mutation breeding for the development of bananas with resistance to race 4, Fusarium wilt (Fusarium oxysporum f. sp. cubense)

In 1985 the Queensland Department of Primary Industries initiated an in vitro mutation breeding program for banana improvement. The primary objective was to develop a banana that was resistant to race 4, Fusarium wilt which could effectively substitute for the Cavendish cultivars currently grown. Micropropagated bananas were exposed to gamma radiation from a 60Co source and the LD50 was established at 40 Gy. However, the optimal dose selected for irradiating explants was 20 Gy. At this dosage visual changes were apparent and plant survival, at 73%, was sufficiently high to make the technique practical on a larger scale. Over 20,000 plants have been evaluated in the field at our race 4 screening site and nursery at Wamuran in southeastern Queensland. Of the irradiated plants examined only the putative mutants from Dwarf Parfitt, an extra-dwarf variety of Cavendish, show potential as a race 4 resistant Cavendish cultivar. Plants are intermediate in height between Dwarf Cavendish and Williams, the industry standard. Preliminary results indicate the putative mutants are faster cycling and more cold tolerant than Williams. More importantly they also appear to retain the resistance to race 4 shown by the mother plant, Dwarf Parfitt. (author). 16 refs, 2 figs, 2 tabs