CITRUS NURSERY SOURCE: NVDMC’s Research Initiatives for 2025–26

By Peter Chaires

Last month’s Citrus Nursery Source article promised additional details on New Varieties Development & Management Corp.’s (NVDMC) 2025–26 sponsored projects. While there is only space for general summaries, it is important to highlight the areas of focus for each research team, and the emphasis on short-term benefits while continuing to build a foundation for the future. NVDMC is proud to sponsor the following projects:

University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Citrus Research and Education Center (CREC) Plant Improvement Team (Fred Gmitter, Jude Grosser, John Chater and Nian Wang)

This team recognizes the urgent need to target scion variety improvement research to best and most quickly address the current challenge imposed by HLB. Balanced against that urgency is recognition of the long-term and incremental nature of citrus genetic improvement and the importance of maintaining and supporting the various processes that are indispensable for future advances in citrus genetic improvement and the delivery of superior new varieties for the Florida industry.

Objective: To invest collaboratively in the future of Florida citrus that can be profitably grown in the HLB-endemic environment. This includes:

• Reassessment of previously released cultivars and unreleased advanced selections under a new regimen of OTC-injection technologies to explore the benefits and risks.
• Documentation of performance attributes of new or recently selected candidates. This work will include sweet orange and orange-like hybrids, grapefruit and grapefruit-like hybrids, and mandarin hybrids for fresh and juice markets.
• Evaluations and selections from populations currently in the field.
• Continuation of core breeding program activities for scion cultivar improvement.
  • Exploit the genetic potential of recently proven improved parents to advance tolerance of HLB and juice quality improvements by creating new families and planting out those families made in the previous season for the same purposes.
  • Continue breeding with a nearly HLB-resistant exotic citrus species that has given rise to hybrids producing sweet orange-like fruits. Some first-generation trees remain PCR negative for CLas after more than seven years in the field in a very high-pressure Asian citrus psyllid and HLB environment.  

UF/IFAS Citrus Breeding, CREC (Manjul Dutt)

Orange juice-processing plants in Florida need more robust early-season sweet orange cultivars to produce Grade A quality juice in December and January. The following projects support evaluation of early-season sweet oranges for their potential tolerance to HLB:

• Short term: Evaluate the Hamlin survivor trees in Lake County and propagate select clones.
• Medium term: Evaluate enhanced HLB tolerance in a replicated Carney 3 sweet orange block.
• Medium to long term: Plant and evaluate existing (mature budwood derived) as well as new early-maturing sweet oranges obtained through seed from the U.S. Department of Agriculture (USDA) in Riverside, California.

UF/IFAS Post-Harvest Evaluation, Indian River Research and Education Center (Mark Ritenour)

1. Determine the ability of fruit from promising new fresh citrus selections, developed by the UF/IFAS and USDA breeding programs, to produce excellent fruit quality and maintain quality after harvest and postharvest degreening treatments (when necessary).
2. Evaluate the effects of preharvest treatments (e.g., OTC trunk injections) of new citrus scion/rootstock selections on fruit quality and shelf life when available.
3. When greater fruit numbers are available, evaluate optimum decay control, storage temperature and handling/treatments during harvest, packinghouse and simulated transportation and marketing conditions.

UF/IFAS Citrus Breeding, Gainesville campus (Jose Chaparro)

• Evaluation of mandarin and orange-like selections for HLB tolerance and juice quality.
  • Each propagated on two rootstocks and planted in two-tree plots.
  • Collection of trait data from two promising tangors that have been selected for release. Morphological and juice quality data will be collected to prepare the documents to support release.
  • Continue to evaluate existing segregating populations to identify additional superior progeny. 
• Accelerated introgression of HLB tolerance from Australian desert lime (Eremocitrus glauca) into commercial citrus germplasm.

USDA-Agricultural Research Service (ARS) Citrus Breeding, U.S. Horticultural Research Laboratory (Matt Mattia)

• NVDMC has supported USDA-ARS in the development of thousands of new hybrids focusing on current processed and fresh fruit needs. Selections have been made for evaluation as HLB-tolerant commercial cultivars, breeding parents and contributions to disease tolerance. This year, trees from these populations will be screened for HLB tolerance and fruit quality and cropping.
• Mattia will establish the “Great American Sweet Orange Trial” that contains more than 60 different mature budwood oranges collected globally and received from the USDA Citrus Germplasm Repository in California. It is intended to identify new alternatives to Hamlin and Valencia that can support the Florida orange juice industry. These varieties have not yet been trialed in Florida since HLB became problematic. Results of this trial will yield orange selections that can be immediately commercialized. In addition, it will provide plant breeders with information of which clones are the most tolerant to HLB and can be used to create novel mutations to improve varieties and create new varieties. 

Peter Chaires is executive director of NVDMC.