Aaron Hewson, a master of science student in plant biotechnology, has been analysing more than 300 varieties from the Jim Dunckley Heritage Orchard.
Established by the Coastal Otago Branch of the New Zealand Tree Crops Association 25 years ago, the orchard is thought to be one of the most diverse collections of apple cultivars in New Zealand, including varieties with colourful names such as Peasgood Nonsuch, Nonnetit Bastard, Warner’s King and Albany Beauty.
"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 were collected in the 1990s by Jim Dunckley from locations across Otago and Southland.
"But the majority came from Clyde, where there was an old Plant & Food [Research] orchard.
"It is a real kind of hodgepodge mix," Mr Hewson said.
Some trees carried names given by local farmers referencing local landmarks such as bridges.
These names did not necessarily match the underlying genetics.
“There is one case where we had a Plant & Food apple called Granny Smith, the classic one you get in supermarkets, and another one 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," Mr Hewson said.
To uncover the underlying DNA, samples were collected by university students and staff from the Plant Biochemistry Lab, labelled and freeze-dried.
They were then sent to a laboratory in France with help from Plant & Food Research, now part of the Bioeconomy Science Institute.
Mr Hewson said his co-supervisor, Dr Elena Lopez-Girona from Plant & Food Research, had been helpful during this process.
"It has been very beneficial to have her expertise."
"They allowed us to send our samples with their bulk group of samples for genotyping by SNP chip."
A SNP chip is a lab process that checks about 50,000 known DNA hotspots in an apple leaf to create a quick genetic fingerprint, showing whether two trees are the same variety or something different.
Biosecurity rules make it difficult to import new apple genetics, so the local collection could prove vital for disease resistance and other traits.
"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 manythere are, they all come from six apples, so it is really, really narrow," Mr Hewson said.
University of Otago Associate Professor Lynnette Brownfield, Mr Hewson’s other co-supervisor, said because commercial apples in New Zealand come from a narrow genetic base, identifying what is in the orchard could help breeders find fresh genes, including disease resistance, to widen future breeding options.
The Coastal Otago Branch of the New Zealand Tree Crops Association owns the orchard and will decide how to use the information, Prof Brownfield said.
The aim was to assign IDs to all trees so the collection was fully known, allowing them to talk with apple breeders from backyard growers to organisations such as Plant & Food Research and to provide germplasm as it was needed, she said.
