Vol 117 (2004): Proceedings of the Florida State Horticultural Society

Importance of postharvest evaluations in a fresh fruit breeding program: usda 77-19 a case in point

T. Greg McCollum
Published December 1, 2004
  • citrus paradisi,
  • bitterness,
  • stem-end rot,
  • ethylene,
  • degreening


Development of new citrus fruit cultivars for the fresh market is recognized as essential for the US citrus industry to remain competitive. The breeding selection USDA 77-19 is a new grapefruit-like hybrid developed by the USDA citrus breeding program. The original hybrid, USDA 75-8, was selected in 1973 from a population of 'Pearl' tangelo × grapefruit hybrids. Budwood of USDA 75-8 was irradiated in 1980 to generate seedless mutants and USDA 77-19 was a low seed content selection made from the irradiated material. Fruit of USDA 77-19 are non-bitter and reach commercial maturity in early September. USDA 77-19 has the potential to fill a niche for an early-ripening low acid non-bitter grapefruit. The fruit have been evaluated in taste tests and have good consumer acceptance. In an effort to determine the market potential for USDA 77-19, we conducted trials to determine the postharvest performance of fruit. We found that USDA 77-19 fruit were highly susceptible to stem end rot, and that the disease was aggravated by exposing the fruit to ethylene. Fungicide treatment reduced the amount of stem end rot, but not to acceptable levels. In addition, in one trial we observed that USDA 77-19 fruit were highly susceptible to chilling injury. Such postharvest problems suggest that USDA 77-19 may only be suitable for local marketing. Results of this work support the concept that development of new fresh market citrus fruit cultivars must include not only field trials, but also postharvest trials to ensure the marketability of the fruit.