Master’s Research Uncovers Genetic Secrets of New Zealand Apples

A master’s student at the University of Otago is conducting groundbreaking research on over 300 heritage apple varieties from the Jim Dunckley Heritage Orchard. Established 25 years ago by the Coastal Otago Branch of the New Zealand Tree Crops Association, this orchard is renowned for its diverse collection, featuring unique cultivars such as Peasgood Nonsuch and Warner’s King. Aaron Hewson aims to leverage genetic analysis to help preserve these historical apple varieties.

Mr. Hewson’s research focuses on identifying and propagating heritage cultivars through genetic means. The apple varieties in the orchard were collected during the 1990s by the late Jim Dunckley, who sourced them from various locations across Otago and Southland. A significant number originated from Clyde, where an old Plant & Food Research orchard was located. Hewson describes the collection as a “hodgepodge mix,” where some trees bear names given by local farmers that reference nearby landmarks. However, these names do not always correlate with the actual genetic makeup of the apples.

A fascinating aspect of Mr. Hewson’s study involved discrepancies in genetic identity. For instance, he discovered that a Plant & Food apple labeled as Granny Smith was genetically identical to another cultivar named Lord Lambourne. This revelation indicates that one of the names may have been incorrectly assigned.

To conduct his research, Mr. Hewson, along with university students and staff from the Plant Biochemistry Lab, collected and labeled samples from the orchard. These samples were freeze-dried and sent to a laboratory in France for genetic analysis with the assistance of Plant & Food Research, which is now part of the Bioeconomy Science Institute. Mr. Hewson expressed gratitude for the support of his co-supervisor, Dr. Elena Lopez-Girona, who has provided invaluable expertise throughout the process.

The genetic analysis employs a technology known as SNP chip genotyping. This method examines approximately 50,000 known DNA hotspots in apple leaves to create a genetic fingerprint, allowing researchers to determine whether two trees are the same variety. The importance of this research extends beyond academic interest; local apple collections may hold the key to disease resistance and other desirable traits as biosecurity regulations complicate the import of new apple genetics.

Mr. Hewson highlighted a startling statistic: while there are around 10,000 apple varieties worldwide, most commercial apples trace their lineage back to only six parent varieties. This narrow genetic base poses risks for future cultivation, making the genetic diversity present in the Dunckley orchard critical for future breeding programs.

Associate Professor Lynnette Brownfield, Mr. Hewson’s other co-supervisor, emphasized the significance of identifying the varieties within the orchard. This knowledge could assist breeders in sourcing new genetic material, particularly traits like disease resistance, thereby enhancing the future of apple cultivation in New Zealand.

The Coastal Otago Branch of the New Zealand Tree Crops Association, which owns the orchard, plans to utilize the findings of this research to assign unique identifiers to each tree. This will create a comprehensive record, enabling collaboration with breeders ranging from backyard growers to large organizations like Plant & Food Research.

The overarching goal is to ensure that this rich heritage of apple cultivars is not only preserved but also actively used in the development of future apple varieties. Through Mr. Hewson’s research, the legacy of these heritage apples continues to thrive, offering promise for the future of apple farming in New Zealand.