Development of bunchy top virus resistant banana cv lakatan in vitro culture and radiation technology

Bunchy to virus (BTV) is the most destructive virus disease of banana in the Philippines. Incorporation of resistance to this virus disease by conventional hybridization is not possible due to male and female sterility of most commercial banana cultivars. In vitro culture coupled with radiation technology can be used to develop BTV resistance in banana cv. Lakatan. The sensitivity of banana shot tip explants to gamma irradiation was determined by subjecting the shoot tips to varying doses (5, 10, 20, 25, 30, 40, 60, 80 and 100 Gy) of irradiation. The LD sub 50 for banana shoot tips determined by 50% reduction in growth and shoot proliferation, was observed to around 20-25 Gy. Bulk irradiation of shoot tip explants was conducted using 20-25 Gy. Irradiated cultures were multiplied for 3-5 cycles and plants regenerated were potted out and screened for BTV resistance. A total of 3,447 irradiated plants regenerated from the radiosensitivity experiment (1,847 plants) and bulk irradiation of 20/25 Gy (1,600 plants) were screened for BTV resistance in the greenhouse using artificial BTV inoculation using the aphid vector Pentalonia nigronervosa. One hundred eighteen plants or 3.4% (118/3,447) of the artificially irradiated plants showed seedling resistance after 4-7 months of evaluation. These plants were planted in the field and were subjected to natural BTV infection. To date, 85 (out of the 118) putative seedling resistant plants continuously expressed BTV resistance in the field after more than 10 months of evaluation. The absence of BTV infection in 39 putative resistant plants was confirmed by ELISA test. Suckers from selected putative resistance plants will be collected, propagated and evaluated for the second cycle stability of BTV resistance and detailed characterization of important horticultural traits