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UF/IFAS Plant Breeding

UF/IFAS Plant Breeding


In Florida, lettuce is primarily planted as a rotational crop with sugarcane and other local commodities on 10,000 acres of rich organic muck soils in the Everglades Agricultural Area (EAA). Florida lettuce is harvested for whole head consumption, packed, and baby leaf production. The crop is planted in protected structures on a small scale with the potential to increase production in these structures. Lettuce represents an 80-million-dollar business to Florida growers and situates the state as the third-largest lettuce producer. Initially, lettuce was introduced as a crop by UF/IFAS researchers in the state of Florida. 

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From the Beginning

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The UF/IFAS Lettuce breeding program started with Dr. Victor Guzman who introduced the crop to the state. However, first attempts to grow lettuce failed early in the 1950s. The crop was finally established in the 1960s thanks to the development of adapted local cultivars by the UF/IFAS lettuce breeding team. 

The UF/IFAS lettuce breeding program has historically worked with growers in the EAA to understand the challenges the growers faced and establish breeding priorities. Some historical cultivars were released by this program including the romaines ‘Tall Guzmaine’ and ‘Short Guzmaine’. Many of these cultivars are used as parents in lettuce breeding programs worldwide. In the United States alone, there is a 25% chance that a modern romaine cultivar has Tall Guzmaine in its pedigree. The cultivar has several good characteristics for the industry, including noticeable disease resistance such as Corky Root Rot caused by a soil-borne bacterium. 

Today and Tomorrow 

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In a subtropical environment such as the one in Florida, disease resistance has been and will remain a priority for the lettuce industry. Sporadic diseases such as Bacterial Leaf Spot will continue to be important in the UF/IFAS lettuce breeding program. Currently, this program has advanced breeding lines that will become cultivars resistant to the strains of Xanthomonas hortorum pv. vitians found in Florida. Research and breeding efforts in diseases such as Fusarium Wilt of Lettuce and Downy Mildew are critical to the industry as well. 

The UF/IFAS lettuce breeding program also focuses on improving issues that will diminish yield in lettuce in a non-predictive environment including heat tolerant cultivars and the improvement of associated disorders to this stress (bolting, tipburn, etc.). Disorders in postharvest such as pinking in lettuce and other leafy vegetables are concerns to growers in the state and this program initiated the work on this issue for Florida Lettuce. 

As more sustainable practices will be in demand in the future, the current UF/IFAS lettuce breeding program is identifying lettuce cultivars that efficiently uptake nutrients focusing on Phosphorus. Eventually, improving lettuce that efficiently uptakes nutrients can translate into savings for lettuce growers. The program is also seeking to improve tolerance to herbicides, as weeds are an enormous issue to lettuce growers, and they are limited by herbicide labels because of the rotational nature of the crop. Additionally, consumers in niche markets like the ones produced in protected structures can benefit from the nutritional content of lettuce. The UF/IFAS lettuce breeding program is working towards growing a more nutritious crop. 

High Impact Releases

The UF/IFAS lettuce breeding program has played a vital role in the advancement of South Florida's lettuce industry by introducing significant cultivars throughout its history. 

'Terrapin' (2000): This romaine cultivar had the highest yield and the highest percentage of marketable heads in variety trials. It can be planted from November to January and harvested from January through March to maximize profits. 

'Florida 1974' (1977): It is a romaine-type lettuce developed by Dr. Victor Guzman and released primarily for breeding purposes. This cultivar possessed two single recessive genes that provided resistance to the Lettuce mosaic virus (LMV) and the Bidens mottle virus (BMoV).

'Floricos 83' (1983): It exhibited distinct characteristics such as more savory, tender leaves, and a milder flavor compared to the widely popular Valmaine cultivar/parent. Floricos 83 was not only resistant to LMV, BMoV, and downy mildew (Texas race), but also demonstrated tolerance to corky root and root rot.

'Floricrisp 1265' and 'Floricrisp 1366' (1984):  Crisp head lettuce cultivars specifically designed for organic soil production by Dr. Guzman. These cultivars underwent extensive testing across multiple locations and were ranked as top performers within their group. Moreover, they exhibited superior internal and external traits when compared to the standard cultivars of its time. Floricrisp 1265 is now used as a breeding parent in other lettuce breeding programs.

'Floribibb' (1984): A butterhead lettuce considered a gourmet lettuce at the time. It showcased resistance to downy mildew race 5, LMV, and BMoV, and despite its susceptibility to corky roots, it managed to produce reasonable yields. Notably, it was reported to contain higher levels of vitamins and minerals compared to its predecessor, summer bibb.

'South Bay' and 'Raleigh' (1984): These cultivars exhibited thermotolerance to temperatures exceeding 90°F, which was particularly advantageous early in the growing season. Additionally, they demonstrated tolerance to corky root, a common issue in South Florida.

Short Guzmaine, Tall Guzmaine, and Floriglade (1986): These cultivars showcased resistance to thermodormancy ( ~90°F), LMV, BMoV, and corky root rot. Short Guzmaine and Tall Guzmaine have since been extensively utilized in various breeding programs to develop new and improved romaine lettuce cultivars.

Florical 48060 and Florical 50011 (1990): Two crisp-head lettuce cultivars with resistance to LMV. Florical 50011 also exhibited resistance to corky roots due to the incorporation of a resistant gene from Green Lakes into Florical 48060. 

A more extended list of cultivars formerly released by the UF/IFAS lettuce breeding program, and their characteristics can be found at HS1225/HS1225: Evaluation of Lettuce Cultivars for Production on Muck Soils in Southern Florida ( 

Research Contacts

Germán S. Miranda

Germán Sandoya

Breeding & Genetics
Horticultural Sciences | Everglades REC


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