Project overview
Heirloom tomatoes are not officially classified as a botanical class but are generally associated with unique shapes, vibrant colors, and rich flavors, which distinguish them from commercial tomatoes. They also often exhibit traceable ancestry and are open-pollinated. This has led to heirloom tomatoes becoming a specialty subclass in the fresh market, despite the lack of established standards and regulations.
While the definition of an heirloom tomato is debated, their distinct characteristics can be objectively analyzed. Previous studies have focused on identifying desirable traits within heirloom germplasm, and this study specifically evaluated the productivity of cultivars from three market classes (traditional heirloom, heirloom hybrid, and commercial hybrid) to determine the most promising cultivars and market class for Hawaiian markets.
Farmer takeaways
- Some traditional heirloom varieties (e.g., ‘Quasimodo’) performed as well as conventional hybrids in the trials, and there is a potential to identify new commercial cultivars that perform well in Hawaii.
- Environmental factors, including disease incidence, played a large role in cultivar performance over the two year study, thus more testing is recommended for HI.
Project objectives and approach
Evaluate the productivity of heirloom and heirloom-like tomato cultivars
In 2020 and 2021, field trials were conducted at the University of Hawaii research stations on Oahu to evaluate three market classes of tomatoes: THs (cultivars recognized as heirlooms), HHs (hybrids marketed as having heirloom-like characteristics or an heirloom parent), and CHs (conventionally marketed hybrids). The field tests were conducted in high-tunnel screenhouses to mitigate pest and disease pressure. Over a 10-week harvest period, data was collected on total and marketable yield.
Evaluate the quality of the heirloom and heirloom-like tomato cultivars
For each variety, 20 red-ripe fruits were harvested and analyzed using the Tomato Analyzer to assess fruit morphology and color. In addition, the fruit quality attributes of total titratable acidity (TTA), total soluble solids (degrees Brix), and pH were evaluated.
Key findings
- The 2020 trial found the highest yields among determinate conventional hybrids, specifically ‘Skyway’, ‘Cypress’, and ‘Grebe’. Surprisingly, the disease-susceptible heirloom variety ‘Quasimodo’ performed best in 2021 and comparably to the top two commercial hybrids in 2020. ‘Ginfizz’, also susceptible to disease, showed consistent and early yields.
- Another unexpected result was the heirloom variety ‘Old German’ outperforming several commercial hybrids in total and marketable yields. Additionally, heirloom varieties had slightly higher total acidity than conventional hybrids.
- Due to the likely influence of environmental conditions, further research is needed before providing recommendations to growers.
Resources
Bryant, G., Kantar, M., Wang, K., Uyeda, J., Ahmad, A., & Radovich, T. (2025). Identification of Promising Heirloom Tomato Varieties for Production in Hawaii. HortTechnology, 35(2), 241-248.
Read MoreLocation
HawaiiCollaborators
Michael Kantar, Koon-Hui Wang, Jensen Uyeda, Amjad Ahmad, Theodore Radovich, University of Hawaii, Manoa
Region
Western
Topic
Plant Breeding, Varieties, and Seeds
Category
Vegetables/Fruits
Year Published
2025
