2019 ASHS Annual Conference

Aerial coverings within high tunnels (HTs) modify crop microenvironments, which is especially important fall-to-spring in mid and upper latitudes. These microenvironments often increase yield but their influence on pigmentation and other variables shaping consumer sensory appeal are unclear. We are investigating sensory responses using panel evaluations of ‘Outredgeous’ red lettuce (Lactuca sativa) exposed to four aerial covering schemes for seven weeks then harvested at baby stage. Twenty 4.5-m² beds in a 9.1 m x 24.4 m HT in Wooster, Ohio were seeded in Fall 2017, Spring 2018, Fall 2018, and Spring 2019. All treatments began at approx. 80% plant emergence and involved the use of 0.03-mm thick vented polyethylene film and/or heavyweight row cover (50-AG Agribon): (1) covered with film always and row cover at night (“F-RC”); (2) covered with film always (“F”); (3) covered with row cover at night (“RC”), and; (4) uncovered (“C”). Row cover was in place daily beginning 15:00 to 18:00 and removed between 8:00 and 10:00. All vegetative tissue 1 cm above the soil line was sampled from 0.3-m² quadrats at weeks four and seven for measurements of fresh and dry weight, leaf area, total soluble solids (˚Brix), and total anthocyanin concentration. Environmental data were recorded seeding to harvest. Nightly row cover (F-RC and RC) treatments increased fresh weight and leaf area compared to beds without (F and C) in Fall runs. Sensory panels in Fall-2018 used material collected at week 7. First, in discrimination-based triangle tests, panelists were asked to differentiate treatment samples based on color. Second, panelists were asked to rank samples according to leaf color intensity and color distribution. Third, panelists were asked to indicate their preference for treatment samples included in a mesclun mix using a hedonic scale. In triangle tests, panelists responded correctly in all but two treatment comparisons (F vs C and F vs F-RC); samples in all other comparisons could be differentiated visually. C and RC treatments were ranked as more intensely red than F and F-RC treatments. Leaf red coloration was comparatively less evenly distributed in the F-RC treatment. Panelists indicated a similar liking for all samples when included in a mesclun mix. Preliminary lessons from this work include: (a) aerial covering programs can influence yield and (b) although leaves were identified as different when directly compared, differences did not affect preference for any treatment when incorporated into a mix, as baby red lettuce is commonly marketed.