Mutation breeding of Highgate (Musa acuminata, AAA) for tolerance to Fusarium oxysporum f. sp. cubense using gamma irradiation

Explants of in vitro-grown cultures of banana (Musa spp., AAA Group cv. Highgate) were exposed to various doses of gamma radiation to evaluate the effectiveness of inducing mutations and also with the aim of producing variants tolerant to the fungus Fusarium oxysporum f. sp. cubense. This fungus causes fusarial wilt or Panama Disease in banana and plantain. Based on phenotypic variations in regenerated plants, factors of effectiveness were calculated for each type of explant. Factors of effectiveness for Types I and III explants (recently dissected apices and corms respectively) showed a similar trend and were higher than that from Type II explants (apices cultured in liquid medium for 28 days). The highest factors of effectiveness were obtained at doses of 0.8 and 2.0 krad for explant Types I and III respectively. Regenerated plants were screened for tolerance to the fungus under greenhouse conditions. Twelve weeks after inoculation, 9 (0.9%), 3 (0.3%) and 8 (0.5%) plants regenerated from explant Types I, II and III respectively had less than 10% vascular invasion of their corms with no external symptoms of the disease. These plants were considered tolerant to the fungus and were multiplied, ex vitro, for field screening.