Student Uncovers Genetic Diversity in New Zealand’s Heritage Apples

Aaron Hewson, a master’s student in plant biotechnology, is conducting significant research on over 300 apple varieties from the Jim Dunckley Heritage Orchard in New Zealand. This orchard, established by the Coastal Otago Branch of the New Zealand Tree Crops Association 25 years ago, boasts one of the most diverse collections of apple cultivars in the country. Varieties include uniquely named apples such as Peasgood Nonsuch, Nonnetit Bastard, Warner’s King, and Albany Beauty.

Hewson’s research aims to aid in the preservation and propagation of these heritage cultivars. “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 explained.

The orchard’s apple cultivars were originally collected in the 1990s by Jim Dunckley from various locations in Otago and Southland, with a significant portion coming from Clyde, where there was once an old Plant & Food Research orchard. Hewson describes the collection as a “real kind of hodgepodge mix,” noting that some trees carry names given by local farmers that reference local landmarks. These names do not always align with the actual genetic identities of the apples.

For instance, he highlighted a case where a well-known cultivar, Granny Smith, was found to share genetic material with a 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,” Hewson stated.

To clarify these genetic relationships, samples were collected by university students and staff from the Plant Biochemistry Lab, where they were labelled and freeze-dried. These samples were subsequently sent to a laboratory in France for analysis, facilitated by Plant & Food Research, now part of the Bioeconomy Science Institute.

Hewson acknowledged the support of his co-supervisor, Dr. Elena Lopez-Girona from Plant & Food Research, stating, “It has been very beneficial to have her expertise.” The samples were sent alongside a bulk group for genotyping using a SNP chip—a method that examines approximately 50,000 known DNA hotspots in apple leaves to produce a genetic fingerprint. This process helps determine whether two trees are the same variety or different.

The significance of this research extends beyond mere identification. With stringent biosecurity rules making it challenging to import new apple genetics, local collections like the Jim Dunckley Heritage Orchard could be crucial for developing disease-resistant varieties and enhancing genetic diversity. “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, they all come from six apples, so it is really, really narrow,” Hewson pointed out.

The potential impact of this research is underscored by insights from Associate Professor Lynnette Brownfield of the University of Otago, who serves as another co-supervisor. She noted that the narrow genetic base of commercial apples in New Zealand necessitates the identification of unique traits within the orchard. This knowledge could assist breeders in sourcing fresh genes, particularly those that confer disease resistance, thus expanding future breeding opportunities.

The Coastal Otago Branch of the New Zealand Tree Crops Association owns the orchard and will determine how to utilize the research findings. Professor Brownfield stated that the goal is to assign unique identities to all trees in the collection. This effort will enable more informed discussions with apple breeders, ranging from backyard growers to organizations like Plant & Food Research, facilitating the provision of germplasm as needed.

As this research progresses, it not only aims to preserve the rich heritage of New Zealand’s apple varieties but also seeks to enhance the future of apple cultivation through genetic diversity and resilience.