Arkansas Fruit Breeder John R. Clark Reflects on 42-Year Career With Division of Agriculture

John Clark began his fruit breeding career in July 1980 as a Research Associate and will retire in January 2023 with the title of Distinguished Professor of Horticulture.

Fred Miller/U of A Systems Division of Agriculture

John Clark began his fruit breeding career in July 1980 as a Research Associate and will retire in January 2023 with the title of Distinguished Professor of Horticulture.

Take a stroll through the fruit aisle of your local grocery store or farmer’s market and you’re bound to find a grape, peach, nectarine, blackberry or blueberry with John Reuben Clark’s fingerprints on them.

During his more than 42-year career at the U of A System Division of Agriculture and Dale Bumpers College of Agricultural, Food and Life Sciences, the Arkansas Agricultural Experiment Station fruit breeder and Distinguished Professor of Horticulture was the developer or co-developer of 81 fruit varieties, including the first primocane-bearing blackberries to flower and fruit on first-year shoots, Prime-Jim® and Prime-Jan®.

According to Margaret Worthington, associate professor of fruit breeding and blackberry genetics, the primocane fruit trait extends the ripening period into late summer and fall, extending the domestic production and marketing season from one to two months of summer to potentially more than six months at the experimental station. The fruit trait, Primocane, also expanded production to new areas of the world and facilitated organic production, Worthington added.

Clark will officially retire from the Division of Agriculture at the end of January.

“Dr. Clark and his program have transformed the small fruit industry domestically and around the world,” said Wayne Mackay, Horticultural Division Manager. “He has a unique ability to imagine what the consumer wants and then create strains that meet that need.”

According to Mackay, Clark has also successfully worked with the berry industry to successfully commercialize new varieties.

“This is most evident in its germplasm licensing, which has enabled the industry to create new flavored table grape cultivars like Cotton Candy that have transformed consumer expectations in this product category,” said Mackay. “He really is a game changer.”

Clark said at the fruit store, “Quality is key” because there are so many new varieties and there is competition among fruits.

“I wouldn’t have said that 40 years ago,” Clark said. “I would have said the most important thing is that we need thornless blackberries and a high yield.”

After developing thornless blackberries and developing many other beneficial traits for fruit growers, Clark’s work focused more on consumer taste and shipping characteristics that extend the fruit’s viability.

Pioneer in patent licensing

The Bayh-Dole Act of 1980 allowed universities and not-for-profit research organizations to own, patent and commercialize inventions developed under government-funded research programs. Although Clark’s predecessor, James Moore, began patenting cultivars in the early 1980s, Clark expanded the intellectual property program, including increased licensing of cultivar patents and the establishment of breeding and testing agreements for the Division of Agriculture, beginning in the early 2000s years. This focus later coincided with the development of the Technology Commercialization Office. The intellectual property proceeds fully support the Arkansas Fruit Breeding Program, Clark said.

“In addition to his creative eye as a plant breeder, John has a creative perspective on the commercial and marketing side,” said Nathan McKinney, Associate Director of the Arkansas Agricultural Experiment Station and former Technology Licensing Officer in the Technology Commercialization Office. “John managed to combine science and business like no other faculty.”

Many of the varieties Clark developed have been successful, Worthington said, particularly for the blackberry industry.

In addition to strains released directly from the Arkansas Fruit Breeding Program, Clark has also worked with staff at Driscoll’s, International Fruit Genetics and other companies around the world to create new strains through breeding agreements using the unique genetics created in the program develop. Innovative table grape flavors have been carried over from Arkansas into IFG proprietary varieties, with the trademarked Cotton Candy and Candy Hearts being some of the most popular examples. The unique flavors developed in Arkansas have attracted attention in the table grape industry worldwide, Worthington said.

pass it on

Though a world-renowned fruit grower himself, since 2013 Clark has also earned a musical reputation for the melodic guitar instruments he composed to accompany the Division of Agriculture’s YouTube videos describing new fruit varieties from Arkansas. The videos were inspired by Dave Edmark, former Experiment Station science writer. Fred Miller, Science Editor and Experiment Station photographer, produced the original videos and recorded Clark’s music.

Clark has narrated 29 videos and provided original compositions such as “Table Grape Getalong” that accompanied the release of a group of table grape varieties. The videos have been viewed over 350,000 times.

Sometimes Clark wrote strain-specific tunes like “Traveler” and “Dazzle” that musically capture the characteristics of the fruit. For example, the song for Prime-Ark® Traveler Blackberry has melodies that “walk” up and down the fretboard to emphasize the strain’s “travel and transport qualities.” The pink grape Dazzle called for “flat-picking” to give it “a little zip,” Clark said.

Clark is also a regular columnist for cultivation of products and American fruit grower Magazine. He has authored over 800 publications in his career, including nearly 400 service and popular press articles, 12 book chapters, and 186 peer-reviewed publications.

From the beginning

Clark began his journey in plant breeding with the Arkansas Agricultural Experiment Station in early July 1980 as a research assistant to Moore, the founder of the fruit breeding program. Clark came to Fayetteville from their home state of Mississippi with his wife, Sharon, and their one-year-old son, Johnathan. Clark earned his bachelor’s and master’s degrees in horticulture from Mississippi State University and was raised on the JR Clark Dairy Farm in Madison, Mississippi, where his family also raised beef cows and row crops.

Farming was an inherent part of his constitution, he says, but fruit growing was outside his purview until he came to Fayetteville about a year after attending a grape growers’ conference at the division’s fruit research station near Clarksville. He also knew a U-of-A student, Keith Patterson, at Mississippi State, who would tell him stories about Fayetteville’s amenities, such as the Swinging Door music club on Dickson Street, where Patterson had worked as a bartender.

Aiming to continue his education in horticulture, a job at Moore, which paid $12,000 a year in 1980, allowed him to continue his PhD by taking one course per semester while working at the Agricultural Research and Extension Center in Fayetteville . In 1983 he received his PhD. and became resident director of the Fruit Research Station and continued to work with Moore on fruit breeding projects until 1996, when Moore retired and Clark relocated to the Fayetteville campus.

Arkansas genetics for everyone

Although the fruit breeding program has always focused on improving varieties for Arkansas, the genetics from these developments are sometimes more valuable to out-of-state growers, Clark said.

“The breeding program is designed to help Arkansas breeders,” Clark said. “That’s our primary focus, so anything that works in other places or if the genetics have value elsewhere is always secondary to Arkansas growers.”

McKinney said, “The impact of John’s career is truly global, but his focus on ‘Arkansas first’ has never waned.”

“It was a fabulous opportunity,” Clark said. “Inspiration is what helps make things happen for you and drives enthusiasm, which expands those possibilities. I’m grateful to have worked for an organization that supported these opportunities. It was a lot of work, and I don’t know how many gallons I’ve sweated, but it really took something the way it worked out.”

Awards and other achievements

Throughout his career, Clark has received some of the highest honors from the Division of Agriculture and professional organizations such as the American Society for Horticultural Science and the American Pomological Society. He has served on numerous horticultural and fruit breeding committees and boards and advised four Ph.D. students, 11 master students and 13 bachelor students. Many have led breeding and research programs in the public and private sectors. He has also served as an informal mentor to many young researchers and consultants around the world. Clark was inducted into the Arkansas Agriculture Hall of Fame in 2018.

To learn more about the Division of Agriculture’s research, visit the Arkansas Agricultural Experiment Station website: Follow @ArkAgResearch on Twitter. To learn more about the Division of Agriculture, visit Follow us on Twitter at @AgInArk. To learn more about extension programs in Arkansas, contact your local Cooperative Extension Service representative or visit

About the Department of Agriculture: The mission of the University of Arkansas Systems Division of Agriculture is to strengthen agriculture, communities and families by combining trusted research with the adoption of best practices. Through the Agricultural Experiment Station and Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the statewide land grant education system. The Department of Agriculture is one of 20 units within the University of Arkansas system. It has offices in all 75 counties in Arkansas and faculties at five system campuses. The University of Arkansas System Division of Agriculture provides all of its extension and research programs and services without regard to race, color, sex, gender identity, sexual orientation, national origin, religion, age, disability, family or veteran status, genetic information, or to any one other legally protected status and is an Affirmative Action/Equal Opportunity Employer.

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