The Ichang lemon and Changsha tangerine have been growing in the Tifton area for more than 35 years. Both are cold-tolerant and produce desirable backyard fruit. The only disadvantage, however, is that the fruit is seeded.

In 2003, Wayne Hanna, crop and soil sciences professor at the University of Georgia Tifton Campus, initiated a project to produce seedless fruit from these two cultivars. Today, Hanna has more than 100 trees of each variety growing on the Tifton Campus. His research program employs the talents of one technician and one ABAC student and part-time assistance from cooperators.

Most citrus trees reproduce via apomixis, a genetic mechanism that allows vegetative reproduction through the seed. In apomixis, a plant produces identical plants via the seed. The goal of the citrus program at the UGA Tifton Campus is to prevent the plant from producing seed, therefore producing seedless cold hardy tangerines and lemons.

“Seed and pollen sterility is one of the main reasons for this program’s success,” Hanna said. “Seedless fruit is more enjoyable to eat.”

One of the ways to produce seedless fruit, according to Hanna, is gamma radiation. At the outset, researchers apply radiation (in various amounts) to seeds. This irradiated seed is then used to produce trees.

Radiation damages the chromosomes, oftentimes resulting in seedless fruit. This process usually produces trees with only one or more limbs with seedless fruit. Once limbs with seedless fruit are identified, buds are taken from the limbs and grafted or budded onto hardy rootstock.

“The amount of radiation applied and the area of the growing point in the seed affected determine whether a branch or entire tree may produce seedless fruit.  As the branches on the tree produce fruit, the fruit on each limb is examined to find seedless fruit,” Hanna explained.

Data collected in 2009 reveal significant reduction in the number of seeds per fruit.  Juice volume is down a little, but not significantly.  The brix level (percentage of sugar) has been maintained and, in some cases, is actually higher.  This means a sweeter fruit.  

Results from the project, thus far, are positive.  So positive, in fact, that Hanna is moving on to the next step:  evaluating the trees’ performance in South Carolina, North Carolina, Louisiana, Texas and Mississippi.  Hanna’s goal is to establish the trees from Texas to North Carolina.

“If you want a seedless lemon or tangerine in your backyard, you can have it in a few years,” said Hanna.

Hanna estimates that the seedless Ichang lemon and Changsa tangerine will be available to the public in three to five years.  In the meantime, however, Hanna is considering other “seedless” options, including kumquat, pomegranate and grapefruit.  Hanna even has his sights set on a coneless pine tree.

“I have nothing to gain [personally] in doing this,” Hanna said.  “I just want to make a contribution to society.”