A Look at What’s in the Citrus Breeding Project Pipeline

The 2021-2022 citrus season is upon us and New Varieties Development & Management Corp. (NVDMC) has a busy slate of projects lined up, subject to funding approval. Like other organizations in these challenging times, the NVDMC board of directors is gearing-up to do more with less. Citrus breeding projects are focused on specific industry needs in an effort to continue development of new crosses while supporting efforts to mine the rich varietal pipeline established in recent years.

Readers often inquire about the nature and scope of these citrus breeding projects, so let’s take a quick look at some of them.

USDA-ARS

The USDA citrus breeding program has been underway for 128 years and has been the source for many scion varieties grown in Florida, with ‘Minneola’, ‘Honeybell’, and ‘Flame’ grapefruit likely the most famous. USDA has been the world leader in developing scion types with useful traits derived from trifoliate orange, including HLB-tolerance, such as in ‘US-SunDragon’.

For the last 16 years, NVDMC funding has permitted greater acceleration of this program. Since 2010, more than 37,000 new hybrids have been produced from more than 700 parental combinations. With USDA’s depth of material, they call on a great diversity of parents and emphasize recent selections to maximize genetic recombination. Parents are selected and crosses directed at producing sweet-orange-like, grapefruit-like, and mandarin-type final releases, with seedlessness a priority in fresh-fruit types.

With so many new hybrids, USDA’s evaluations are entering a new phase with data-intensive assessment of selected populations each year. Assessments include fruit quality evaluations, funded separately, and additional funds are being sought to fully implement genomic science in the USDA program. This new hybrid diversity will be tapped to provide productive cultivars producing high-quality fruit and juice where HLB is widespread, with a strong emphasis on sweet orange-like hybrids.


UF/IFAS CREC Plant Improvement Team

Although every year the nature of the work is the same that the UF/IFAS Citrus Research and Education Center citrus breeding team conducts with support from the NVDMC, on behalf of the Florida industry, every year also is a new year in the cycle of plant improvement. There are new crosses to be made, frequently using for the first time new and improved breeding parents that have come about because of the many years invested in breeding and selection, and sometimes new crosses are made based on the performance results we see in families created previously that highlight the superiority of some parents over others.

These days, our focus has been and will continue to be directed at the primary objective of developing new varieties that can be grown successfully and profitably. Successfully means trees that can yield good crops of fruit from trees that withstand the onslaught of HLB. Profitably means the fruit they produce in abundance have the necessary quality attributes to meet the marketplace demands and to earn growers good profits.

Oranges and HLB-tolerant hybrids that produce sweet orange-like fruit are of critical importance to our industry and, therefore, to our breeding program, so substantial attention is directed at creating, evaluating, selecting, and moving forward new selections to meet the needs of the juice business. But we also serve the fresh industry as well. Based on recent new selections we have seen from certain crosses for grapefruit improvement that are tolerating HLB much better than the standard varieties grown, we are making crosses with new parental combinations using parents we created before. We make new crosses for mandarin improvement as well, always looking for larger, sweeter, more colorful seedless fruit on HLB-tolerant trees that mature across the season to provide fresh growers more options to exploit seasonal marketing niche opportunities, as mandarin production globally has become commoditized. And we are looking forward to releasing three seedless lemon selections we have developed to serve the growing interests in lemon production in Florida.

Postharvest trial of Vernia oranges

Citrus breeding research of many aspects are in the works, like Dr. Mark Ritenour’s studies on the use of ethephon (an ethylene-releasing compound) in the field one week prior to harvest to improve peel color on ‘Vernia.’
Photo by Mark Ritenour

Every year brings new selections to our attention, and these must be rigorously evaluated and compared with industry standards as well as our previously identified hybrids. We do this always with as much involvement as we can have from all aspects of the Florida citrus industry. That includes the growers, obviously, who are the backbone of the entire enterprise, but also the processors, the packers and shippers, and even the retailers and consumers when possible. One way we collect the needed feedback is through our four to five Fruit Display Days that we are very much looking forward to resuming in the coming season. We also participate in the major trade shows throughout the state. We regularly host interested growers to visit our demonstration planting in Lake Alfred, and we likewise will continue to visit growers throughout the state who host our field trials and plantings. There can never be too much two-way communication.


UF/IFAS Gainesville Breeding

NVDMC-supported research efforts of the UF Gainesville Citrus Breeding program are focused on several areas with an emphasis on HLB tolerance and desirable traits. During the 2021-2022 season, the trial plots of seedless mandarin and sweet orange-like selections, established at Indian River Research and Education Center in cooperation with Dr. Lorenzo Rossi, will be evaluated for fruit quality traits and tree health. A second, smaller replicate plot established in the Teaching Grove in Gainesville will also be evaluated. Data from these trial plots is being used to facilitate the release of ‘Sherman’, an early ripening sweet orange-like selection and ‘Sunray’, an early ripening seedless mandarin-like selection.

Hybrids focused on generating new grapefruit varieties are being developed. The ideotype desired is a canker- and HLB-resistant, lycopene accumulating seedless grapefruit. HLB-tolerant, seedy, white-fleshed, grapefruit-like selections have been generated, and next year’s crosses will be oriented toward transferring lycopene accumulation and the seedless trait into the populations.

Breeding populations derived from hybridizing Australian Desert Lime (Eremocitrus glauca) with commercial citrus are being evaluated for HLB tolerance and fruit quality traits. Progress in improving commercial traits such as fruit and flesh color, fruit size and soluble solids content, while retaining HLB tolerance is being evaluated.

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