Research Uncovers Genetic Diversity of New Zealand’s Heritage Apples

A significant research initiative is underway at the Jim Dunckley Heritage Orchard in New Zealand, where Aaron Hewson, a master of science student in plant biotechnology, is analysing over 300 varieties of apples. Established 25 years ago by the Coastal Otago Branch of the New Zealand Tree Crops Association, this orchard is considered one of the most diverse collections of apple cultivars in the country.

Hewson’s research aims to support the preservation and propagation of these heritage varieties through genetic identification. “I am doing this research for them so they can continue to preserve and propagate the heritage cultivars, with confident identification by genetic means,” he stated. The apple cultivars were gathered in the 1990s by Jim Dunckley from various locations across Otago and Southland, with the majority originating from Clyde, the site of an old Plant & Food Research orchard.

Many of the apples in the orchard have names assigned by local farmers, often based on regional landmarks such as bridges. Hewson noted that these names sometimes do not correspond with the actual genetic makeup of the apples. For example, he highlighted a case involving a commonly known cultivar, Granny Smith, which was found to be genetically identical to another variety called Lord Lambourne. “These two cultivars should be really different, but the samples were saying they were genetically the same. So one of those names has to be wrong,” he explained.

To determine the genetic identity of these apples, samples were collected by university students and staff from the Plant Biochemistry Lab. The samples were then freeze-dried, labelled, and sent to a specialized laboratory in France for analysis, with logistical support from Plant & Food Research, now part of the Bioeconomy Science Institute. Hewson expressed gratitude for the assistance of his co-supervisor, Dr. Elena Lopez-Girona, in facilitating this process, stating, “It has been very beneficial to have her expertise.”

The genetic analysis employs a technique known as the SNP chip, which examines approximately 50,000 known DNA hotspots in apple leaves. This method generates a genetic fingerprint that can quickly determine whether two trees belong to the same variety. The research is particularly important given the stringent biosecurity regulations that complicate the importation of new apple genetics into New Zealand. As Hewson pointed out, “If we talk about the entire amount of apples across the world, there is something on the order of 10,000 different varieties. But all of our commercial varieties, no matter how many there are, come from just six apples.”

Associate Professor Lynnette Brownfield, who also supervises Hewson, emphasized the significance of identifying the genetic diversity within the orchard. She noted that since commercial apples in New Zealand stem from a limited genetic pool, uncovering the unique traits of these heritage varieties could aid breeders in discovering fresh genetic resources, including traits for disease resistance.

The future of this research hinges on the decisions made by the Coastal Otago Branch of the New Zealand Tree Crops Association, which owns the orchard. Professor Brownfield highlighted the project’s ultimate goal: to assign unique identifiers to all trees in the collection, enabling comprehensive knowledge of the varieties. This will facilitate collaboration with apple breeders, ranging from backyard enthusiasts to larger organizations such as Plant & Food Research, ensuring that valuable germplasm is made available as needed.

As this research progresses, the insights gained could play a crucial role in enhancing the resilience and diversity of apple cultivars in New Zealand, securing a future where heritage varieties continue to thrive.