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  • Author or Editor: Catherine E. Belisle x
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Pink rib discoloration or pinking in the midribs of lettuce (Lactuca sativa) leaves is a stress-induced disorder that leads to crop loss worldwide. Maintaining recommended field and postharvest conditions reduces its incidence but does not eliminate the issue. During the past decade, research has identified the tolerance of this disorder among lettuce types and cultivars grown in cooler climates. However, tolerance to pink rib among lettuce types grown in humid subtropical climates is unknown; therefore, it is necessary to screen lettuce germplasm under these growing conditions. During this study, diverse lettuce accessions were planted for early-season, mid-season, and late-season harvests over two seasons in Belle Glade, FL, USA. Harvested midribs were wounded to induce pink rib, stored for 6 to 9 days at 5 °C and >95% relative humidity, and rated for severity using a 5-point subjective scale. Genotype × environment interactions were evaluated to understand the environmental factors that favor the development of pink rib during storage and between planting seasons. Pink rib severity increased during storage, with the highest increase observed after 3 to 4 days in both seasons. After 9 days of storage, lettuce accessions with the least pink rib for each leaf type were identified. The lowest pink rib ratings after 9 days of storage were “moderate” (rating of 3) for crisphead, Latin, and romaine, “slight” (rating of 2) for butterhead types, and “none” (rating of 1) for leaf types. Additionally, pink rib severity increased among accessions during the late spring season harvest when field temperatures were higher and daylight hours were extended. The lettuce germplasm with low susceptibility to pink rib is promising to breed lettuce lines for future research.

Open Access

The postharvest life of lettuce (Lactuca sativa) is variable and negatively affected by mechanical injury, incomplete cooling, and poor genetic quality. Lettuce breeders are developing cultivars with a longer shelf life and rely on subjective, destructive, and time-consuming methods for quality analysis. One method of accelerating quality evaluations is known as accelerated shelf-life testing (ASLT), which has the potential to assist breeders in assessing lettuce quality and shelf life. The objective of this research was to determine the quality traits that significantly affect shelf life to develop an ASLT procedure to rapidly assess the postharvest quality of lettuce accessions in breeding programs. In Test 1, Romaine lettuce quality was evaluated using one subjective and five objective parameters during storage at 5, 10, 15, or 20 °C. Results determined that weight loss, lightness*, and hue* angle were best correlated with the overall appearance rating, whereas storage at 10 or 15 °C differentiated the shelf-life potential quickly and without excessive deterioration. In Test 2, these objective characteristics and storage temperatures were used to study rates of quality deterioration of a commercial Romaine cultivar (Okeechobee) and a breeding line (60182), both with long shelf lives, and a Batavia lettuce cultivar (La Brillante) with a short shelf life. Lettuce was evaluated during storage at 10 °C (winter and spring seasons) or at 15 °C (winter season). Weight loss was the most appropriate quality index for lettuce at these storage temperatures for a single harvest, whereas lightness* and hue* angle were the most appropriate indices for comparing quality between harvests. To apply ASLT to postharvest assessments of lettuce, breeders and other researchers should include two controls with good and poor shelf life (similar to ‘Okeechobee’ and ‘La Brillante’, respectively) as standard baseline cultivars during storage at either 10 or 15 °C.

Open Access