Researchers at The University of Queensland have pinpointed a genetic region in a wild banana that resists Fusarium wilt Subtropical Race 4, a threat to Cavendish bananas worldwide. The discovery, from the wild variety Calcutta 4, offers breeders a tool to develop disease-resistant commercial bananas. This five-year study provides a roadmap for sustainable protection against the soil-borne fungus.
A team led by Dr. Andrew Chen and Professor Elizabeth Aitken at The University of Queensland has identified the genomic region on chromosome 5 of the wild diploid banana Calcutta 4 that confers resistance to Fusarium wilt Subtropical Race 4 (STR4), a variant of Panama disease. This fungus, which spreads through soil and persists to infect future crops, endangers global Cavendish banana production in subtropical regions.
"Fusarium wilt -- also known as Panama disease -- is a destructive soil-borne disease which impacts farmed Cavendish bananas worldwide through its virulent Race 4 strains," Dr. Chen explained. The pathogen causes plants to wilt and die, leaving lasting contamination that challenges conventional farming.
To locate the resistance, researchers crossed Calcutta 4 with susceptible diploid bananas, grew the progeny, and exposed them to STR4. They then compared DNA from surviving plants and those infected, using forward genetics, genome sequencing, and bulked segregant analysis. "We've located the source of STR4 resistance in Calcutta 4... This is a very significant finding; it is the first genetic dissection of Race 4 resistance from this wild subspecies," Dr. Chen stated.
The effort spanned five years, with each banana generation requiring at least 12 months to mature for testing and breeding. Although Calcutta 4 is fertile, its fruit is not edible, making it unsuitable for commercial use. Instead, the findings aim to guide breeding of palatable, resistant varieties.
Future work will develop molecular markers for early detection of the trait, accelerating selection and reducing costs. "The next step is to develop molecular markers to track the resistance trait efficiently so plant breeders can screen seedlings early," Dr. Chen said. The study, funded by Hort Innovation and the Australian Government, appears in Horticulture Research.