What’s Next for the Donaldson Citrus Variety?

Josh McGillHLB Management, Research

During this summer’s Florida Citrus Industry Annual Conference, Matthew Mattia, a post-doctoral associate with the U.S. Department of Agriculture (USDA), discussed his work to identify the origins of the Donaldson citrus variety. The variety is a single tree on the USDA A.H. Whitmore Foundation Farm near Groveland, Florida.

Matthew Mattia spoke about the Donaldson variety at the Florida Citrus Industry Annual Conference.

Mattia was the first to discover the tree on the farm in July 2021. The tree caught his eye because of its healthy appearance despite high HLB infections in the grove. Mattia pored through thousands of USDA records trying to discover the origin of the variety but was unable to conclusively find it. He found records of the tree dating back to the 1950s and is fairly confident it was propagated in Florida.

While the origin is unknown, the tree has created a buzz because of its tolerance to HLB. Mattia addressed what’s next for the tree during the conference. A team of scientists is being assembled to study all aspects of the tree.

“We have been taking cuttings off this tree and budding those on rootstocks,” Mattia said. “These roots are dipped in antibiotic material to clean up the HLB. We want cleaned material so we can look for early interactions with HLB. This might tell us more about overall tolerance and how we might expect the variety to perform in the grove.”

Donaldson has been entered into the Florida Department of Agriculture and Consumer Services Department of Plant Industry Accelerated Budwood Initiative. Cleanup of the material began, and genetic sequencing of the original, single tree is being conducted. Genetic work also is underway to confirm the rootstock is indeed Swingle, which it is believed to be.

Tissue culture was successfully used to grow the first 1,088 Donaldson seedlings. The goal is to release tissue-culture trees to nurseries by the end of the year or early next year. Read more about the limited availability of Donaldson.

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Frank Giles


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