Researcher Unlocks Genetic Secrets of New Zealand’s Heritage Apples

A comprehensive analysis of over 300 apple varieties from the Jim Dunckley Heritage Orchard is underway, led by Aaron Hewson, a master of science student specializing in plant biotechnology. This orchard, established 25 years ago by the Coastal Otago Branch of the New Zealand Tree Crops Association, is recognized as one of New Zealand’s most diverse collections of apple cultivars.

The research aims to ensure the preservation and propagation of these heritage cultivars through genetic identification. According to Hewson, “I am doing this research for them so they can continue to preserve and propagate the heritage cultivars, with confident identification by genetic means.” The cultivars in question were collected in the 1990s by Jim Dunckley, who sourced them from various locations in Otago and Southland, predominantly from Clyde, where an older Plant & Food Research orchard was situated.

Hewson describes the collection as a “real kind of hodgepodge mix,” noting that some trees bear names reflecting local landmarks, which do not always align with their genetic backgrounds. For instance, he highlights a case involving a Plant & Food apple called Granny Smith, traditionally found in supermarkets, and another named 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 explained.

To investigate these genetic discrepancies, samples were collected by university students and staff from the Plant Biochemistry Lab, labeled, and freeze-dried. These samples were then sent to a laboratory in France for analysis, with support from Plant & Food Research, now part of the Bioeconomy Science Institute. Hewson credited Dr. Elena Lopez-Girona, his co-supervisor from Plant & Food Research, for her invaluable assistance during the research process.

“They allowed us to send our samples with their bulk group of samples for genotyping by SNP chip,” Hewson stated. A SNP chip is a laboratory technique that examines approximately 50,000 known DNA hotspots in apple leaves, providing a rapid genetic fingerprint to determine if two trees belong to the same variety or differ.

The significance of this research extends beyond mere identification; it addresses crucial issues related to biodiversity. Biosecurity regulations hinder the import of new apple genetics, making the local heritage collection pivotal for enhancing disease resistance and other beneficial traits in apple cultivation. “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 remarked.

Associate Professor Lynnette Brownfield from the University of Otago, who serves as another co-supervisor, emphasized the importance of this research for the future of apple breeding in New Zealand. She pointed out that identifying the genetic composition of the orchard could assist breeders in discovering new genes, including those for disease resistance, thereby broadening the genetic base for future apple varieties.

The Coastal Otago Branch of the New Zealand Tree Crops Association, which owns the orchard, will determine how the findings from this research will be utilized. The ultimate goal is to assign unique identifiers to all trees in the collection, thus enabling comprehensive knowledge of the orchard’s genetic diversity. This information will facilitate discussions with apple breeders ranging from backyard growers to major organizations like Plant & Food Research, and will support the provision of germplasm as needed.

In a world where agricultural biodiversity is increasingly threatened, the work being done at the Jim Dunckley Heritage Orchard stands as a critical effort to preserve heritage apple varieties for future generations.