Abstract
The purpose of this research is to determine how increasing levels of nitrogen (N) fertilizers, locations, and cultivars affected yields, biomass accumulation, and polyphenol concentrations in lettuce. This study is carried out at the North Mississippi Research and Extension Center (NMREC) and Northwest Washington Research and Extension Center (NWREC). The experiment is a randomized complete block design arranged in a 2 × 2 × 4 factorial with 4 replications. Treatments include two cos (romaine) lettuce cultivars, ‘Salvius’ and ‘Thurinus’. N treatments include 42, 63, 105 and 189 kg·ha−1. ‘Salvius’ has greater fresh mass (FM) and dry mass (DM), and a smaller DM:FM ratio when compared to ‘Thurinus’. The NWREC location has higher lettuce FM and DM. Quercetin-3-glucoside (Q-3-G) increases with increasing N concentrations. There are interactions between locations and lettuce cultivars for chlorogenic acid, Q-3-G, and quercetin/luteolin glucuronide (QL-G). There is increased chlorogenic acid content in ‘Salvius’ at the NMREC and increased concentrations of Q-3-G and QL-G in ‘Thurinus’ compared to the NWREC location. ‘Thurinus’ has significantly more chicoric acid and quercetin-malonyl-glucoside (QM-G) than ‘Salvius’. Lettuce at the NWREC has significantly more chicoric acid and cyanidin-3-glucoside (C-3-G). Lettuce at the NWREC has greater yields and biomass accumulation. Lettuce at the NWREC also has greater amounts of flavonoids and anthocyanins. ‘Salvius’ has greater amounts of phenolic acids and ‘Thurinus’ has greater amounts of flavonoids and anthocyanins.
Highlights
Lettuce is among the most widely produced vegetables in the United States
‘Thurinus’ produced a greater dry mass (DM):fresh mass (FM) ratio than ‘Salvius’. These results demonstrated that marketable lettuce produced at the Northwest Washington Research and Extension Center (NWREC) had significantly greater FM and DM than plants grown at the North Mississippi Research and Extension Center (NMREC) (Table 1)
The current study aimed to elucidate the impact that varying rates of N fertilizer may have on the yield and nutritional quality of green and red romaine lettuce cultivars produced in regions with differing climates
Summary
Lettuce is among the most widely produced vegetables in the United States. Since 2012, the acreage devoted to fresh-market lettuce production has been expanding, as production territory has grown and more producers have entered the industry [1,2]. As of 2015, lettuce was considered to be the nation’s most valuable crop after reaching $1.9 billion in sales [2]. Lettuce is a staple food in the American diet and is consumed in large quantities by the public [3]. Lettuce is considered to be a nutritious vegetable due to its high content of calcium, iron, vitamins A and C, and phenolic antioxidants.
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