Resistance sources to Fusarium oxysporum f. sp cubense tropical race 4 in banana wild relatives

Target trait evaluation in crop wild relatives is an important prerequisite for efficiently using the potential useful genes located in this valuable germplasm. Over recent decades, Fusarium oxysporum f. sp. cubense tropical race 4 (Foc-TR4) has seriously threatened worldwide banana plantations. Breeding new resistant cultivars from wild banana species is expected to provide invaluable additional resources. However, knowledge on resistance to Foc-TR4 in wild Musa species is very limited. In this study, eight genotypes of wild banana relatives (Musa acuminata subsp. burmannica, M. balbisiana, M. basjoo, M. itinerans, M. nagensium, M. ruiliensis, M. velutina and M. yunnanensis) were characterized for resistance to Foc-TR4 in both greenhouse and field conditions. Most wild bananas showed higher resistance levels to Foc-TR4 than the reference cultivars 'Brazilian' (AAA, susceptible) and 'Goldfinger' (AAAB, moderate resistance). Among the wild species, M. balbisiana showed the highest levels of disease intensity followed by M. acuminata subsp. burmannica. Some individuals of M. yunnanensis, M. nagensium, M. ruiliensis and M. velutina showed low levels of rhizome discolouration in greenhouse conditions, but were resistant in the field. No symptoms were observed on M. basjoo and M. itinerans, suggesting higher levels of resistance to Foc-TR4. The results revealed different sources of resistance to Foc-TR4 in banana wild relatives, which constitute a valuable genetic resource for banana breeding programmes aiming to produce cultivars resistant to fusarium wilt.