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Citrus Rootstock Guide Updates Available Online

Daniel CooperIndustry News Release, Rootstocks

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(UF/IFAS) — Florida’s citrus growers may now access the updated Florida Citrus Rootstock Selection Guide, which is more user- and mobile-friendly. Revisions include current University of Florida rootstock horticultural traits, three new rootstocks that tolerate citrus greening and an updated bibliography.

“The fourth edition of the Florida Citrus Rootstock Selection Guide has a new look and information for a comprehensive description of standard commercial and recently released rootstocks,” said Rhuanito “Johnny” Ferrarezi, an assistant professor who leads citrus horticultural research and University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Extension programs at the UF/IFAS Indian River Research and Education Center (IRREC) near Fort Pierce. “The rootstock guide saves time for growers and provides a useful tool for rootstock choice that is supported by previous and ongoing field research.”

The updated guide website was funded by the Citrus Research and Development Foundation Inc. and the U.S. Department of Agriculture National Institute of Food and Agriculture.

Adding that the site is easy to reference, Ferrarezi explained that growers who access the site may select from a menu of 21 horticultural traits for 49 different rootstocks. An expert system based on artificial intelligence will then simulate a “human expert” and sort rootstocks that will benefit the growers’ specific needs. The database combines factors such as weather, soil types, water availability and fruit varieties. With just a few clicks, growers can access the best information available about rootstock selection.

Rootstock horticultural traits have been updated for University of Florida rootstocks. Three new rootstocks, US Super Sour 1, US Super Sour 2, and US Super Sour 3, now appear in the rootstock guide. Each of the new Super Sours is expected to tolerate huanglongbing (HLB), or citrus greening, a disease that has challenged the Florida citrus industry.

“The most recently published journal articles and a bibliography from 2015 in which all work relevant to citrus rootstocks are now available,” said Ferrarezi, whose research objective is to determine which rootstocks most effectively resist HLB. “An easy-to-read and attractive chronological timeline for the guide’s history is also included on the site.”

Ferrarezi’s work aims to assist citrus growers in the Indian River District, where the world’s highest-quality grapefruit is produced. He studies ways to improve production inside citrus under protective screen (CUPS), in which citrus trees grow in a protected environment of 14-foot-high white mesh screen houses.

Ferrarezi examines rootstock performance in an experimental grove called the Millennium Block, a 35-acre research plot where citrus research began in 2000. When citrus canker was found on a few trees in the grove in 2005, it was necessary to ‘push’ the entire grove, as mandated by the Florida Citrus Canker Eradication Rule.

Today, nearly 15 years later, and despite one of the district’s lowest points of grapefruit production, Ferrarezi has planted about two-thirds of the 5,440 young citrus trees he will study in the Millennium Block.

“We have a new beginning for the Millennium Block at IRREC, and we will seek scions and rootstocks that best resist huanglongbing,” Ferrarezi said.

Most of Florida’s citrus trees are affected by HLB, Ferrarezi said. As the disease advances, leaves turn to a lighter green, hence its common name. Ferrarezi works along with research professors to develop methods to best manage fruit production on trees that have HLB, to minimize or slow the pathogen’s effects.

Within the guide, Ferrarezi recognizes research collaborators who have made contributions to the guide since it was first created in 1989, as well as those who continue to research rootstocks, which is critical to the industry’s sustainability. They include William Castle, professor emeritus who previously worked at the UF/IFAS Citrus Research and Education Center (CREC) in Lake Alfred; Jude Grosser, UF/IFAS professor of plant cell genetics at CREC; Stephen Futch, multi-county UF/IFAS Extension agent emeritus who also retired from CREC. Also contributing to the guide are Kim Bowman, a geneticist with the U.S. Department of Agriculture’s Agricultural Research Service, who developed the three new Super Sour varieties; and Steve Rogers, a research scientist and website provider who is also the CEO of Ecostat, a private company based in Florida. Rogers created the artificial intelligence system for the guide. Ferrarezi Citrus Horticulture Laboratory webmaster Andres Gonzalez designed and executed the guide.

Source: University of Florida Institute of Food and Agricultural Sciences