Lychee belongs to the Sapindaceae family and is native to southern China. The crop is grown commercially from latitude 17° to 32° and is usually found at low elevation in the subtropics and from 300 to 600 m in tropical locations (Menzel and Simpson, 1994). Except for about 1200 acres grown in south Florida and about 330 acres in Hawaii (Nagao, 2009), lychee is virtually unknown in the western hemisphere.
The most common and recommended method of lychee propagation is by air layering. Trees propagated from air layering come into commercial production about 3 to 5 years after field planting. Trees propagated by seed are slow in growth, not true-to-type, and take many years to bear a crop. Experimentation on optimal plant spacing of lychee is scarce but it is generally recommended that trees be spaced 25 ft within and between rows, which is equivalent to about 170 trees/ha.
Yield varies with cultivar, age of tree, weather conditions, presence of pollinating insects, and management. Insects are necessary for pollination, and honeybees account for about 80% of pollinating insects. An average yield is considered 25–60 kg/tree per year, although yields as high as 90–140 kg/tree per year can be obtained (Crane et al., 2013). Pruning is carried out at harvest with the removal of 15 to 60 cm of the branch with the fruit clusters (Zee et al., 1998). The lychee is a nonclimacteric fruit and as such does not ripen once harvested; therefore, the fruit must be picked at optimal visual appearance and eating quality. Pericarp color is the most commonly used harvest index, but color and fruit maturity varies with cultivars, regions of cultivation, and cultural practices (Underhill et al., 2001). The fruit has a short shelf life of about 2 to 7 d at 25 °C (Underhill et al., 2001). The handling and storage of lychee postharvest are determined by the need to control pericarp browning, which is accomplished by reducing the rate of water loss by various methods (e.g., cooling at 5 °C, use of plastic films for packaging) or by chemical treatments such as sulfur dioxide followed by immersion of fruit in 1 n hydrochloric acid (HCl) for 2 min (Underhill et al., 2001).
There are about 70 known cultivars of lychee, but only a few have been studied or extensively cultivated. The most commercially used cultivars are Kwa Mi, an early cultivar with fruit of excellent quality; Kaimana from Hawaii; Bosworth-3 (Kwai May Pink) and Salathiel are Australian selections that bear fruit regularly; Brewster, a midseason commercial cultivar in Florida; and Groff, a late cultivar that bears regularly in the tropics (Galan-Sauco, 1987; Zee et al., 1998). Most cultivars require a chilling period of about 15 °C for about 10 weeks for flower induction and consequent fruit set although more tropical cultivars are known to flower after a period of 20 °C for 6–8 weeks. To our knowledge, replicated field trials to evaluate these and other lychee cultivars are nonexistent. The objective of this study was to evaluate yield performance and fruit quality traits of six lychee cultivars grown at two locations in the highlands of Puerto Rico.
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