During a recent webinar, Jude Grosser, University of Florida Institute of Food and Agricultural Sciences professor of plant cell genetics, presented a three-legged stool approach to achieving sustainability in citrus production. Those legs consist of:
- Superior rootstock genetics
- Improved scion selections
- An enhanced nutrition program that keeps trees fed with consistent flows of primary and secondary nutrients
For the first two legs, Grosser said enhanced tolerance to HLB is a primary goal, along with improving yield and juice quality. During the presentation, he covered several rootstocks and scions, but the following are a few of particular note.
ROOTSTOCKS
Grosser discussed his favorite new rootstock, which is a mutant of X-639. Many growers are familiar with X-639. The new rootstock is called Defiance.
It creates an excellent root system despite HLB. Grosser showed a photo of 2-year-old OLL-20 trees planted on Defiance with no individual protective covers (IPCS) or oxytetracycline (OTC) injections that were off to a strong start and cropping well.
UFR-18 is another new rootstock release, which has shown good tolerance to diaprepes. It also has screened well for sting nematode tolerance. In addition, the rootstock has also shown tolerance to HLB.
“If you were at the field day at Jason Griffin’s grove recently, you would have seen these trees,” Grosser said. “There’s a block of 10- to 11-year-old trees in his grove that look fantastic and are loaded with fruit.”
SCIONS
Two new varieties — OLL-DC336 and OLL-DC340 — were discussed in Grosser’s presentation. He said these have superior flavor attributes and juice quality and have done well in field trials. Early tolerance to HLB looks promising.
“The trees (from both varieties) are gorgeous,” Grosser said. “They were not grown with IPCs. With the exception of a handful of trees, they have not had OTC, although the ones that did get OTC have done slightly better than the ones without it.”
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