Identification of a QTL conferring resistance to the Subtropical Race 4 of Fusarium oxysporum f. sp. cubense in Calcutta 4 (Musa acuminata ssp. burmannica)

Fusarium wilt of banana (FWB), caused by Fusarium oxysporum f. sp. cubense (Foc), continues to be one of the most devastating diseases of bananas worldwide. The pathogen is highly adaptive, and composed of distinct evolutionary lineages, and three races with pathogenicity to specific banana cultivars. Foc Race 1 decimated the Gros Michel (AAA genome) based banana industry in the 1950s and was replaced with the Cavendish banana, which is resistant to Foc Race 1. Since then, Cavendish has dominated the global market but is susceptible to infection by Foc Race 4, which includes Subtropical Race 4 (STR4) and Tropical Race 4 (TR4). Whereas TR4 infects Cavendish in all environments where banana is grown, STR4 is a lineage closely related to TR4 that causes disease in subtropical regions with cooler climates. Since the 1990s, global banana production has succumbed to TR4, after it was first detected in the Asia-Pacific region. The fungus has since spread to many banana growing regions around the world. In Australia, TR4 remains confined to the Tully Valley in northern Queensland since its first detection in 2015, yet the long-term sustainability of the country’s banana industry is under ongoing threat. With no effective chemical control available, resistance breeding is widely considered the most promising management strategy. Wild diploid accessions of Musa acuminata are key sources of resistance to Foc Race 4. So far, quantitative trait locus (QTL) for STR4 resistance has been identified in M. acuminata ssp. malaccensis [1]. Here we report the first genetic dissection of resistance from M. acuminata ssp. burmannica, another valuable diploid group in banana improvement programs