Phenomic and Physiological Analysis of Salinity Effects on Lettuce

Abstract

Salinity is a rising concern in many lettuce-growing regions. Lettuce (Lactuca sativa L.) is sensitive to salinity, which reduces plant biomass, and causes leaf burn and early senescence. We sought to identify physiological traits important in salt tolerance that allows lettuce adaptation to high salinity while maintaining its productivity. Based on previous salinity tolerance studies, one sensitive and one tolerant genotype each was selected from crisphead, butterhead, and romaine, as well as leaf types of cultivated lettuce and its wild relative, L. serriola L. Physiological parameters were measured four weeks after transplanting two-day old seedlings into 350 mL volume pots filled with sand, hydrated with Hoagland nutrient solution and grown in a growth chamber. Salinity treatment consisted of gradually increasing concentrations of NaCl and CaCl2 from 0 mM/0 mM at the time of transplanting, to 30 mM/15 mM at the beginning of week three, and maintaining it until harvest. Across the 10 genotypes, leaf area and fresh weight decreased 0–64% and 16–67%, respectively, under salinity compared to the control. Salinity stress increased the chlorophyll index by 4–26% in the cultivated genotypes, while decreasing it by 5–14% in the two wild accessions. Tolerant lines less affected by elevated salinity were characterized by high values of the chlorophyll fluorescence parameters Fv/Fm and instantaneous photosystem II quantum yield (QY), and lower leaf transpiration.

Response to Salt Stress in Lettuce: Changes in Chlorophyll Fluorescence Parameters, Phytochemical Contents, and Antioxidant Activities

“…All other CF parameters showed either significant positive or negative correlations with each other. Chlorophyll content exhibited a strong positive correlation with Fv/Fm, Y(PSII), qN, and Rfd, which is somewhat similar to previous reports [21]. However, the magnitude of the correlation was different, probably due to the difference in the sensitivity of the lettuce genotype used in this study.…”

“…These health benefits have been linked to a range of micro-and macro-nutrients, Sensitivity to salt stress differs with the various stages of a plant's development [9,17], with stronger responses during reproductive stages than in early growth [17]. In lettuce, several studies have been performed using chlorophyll fluorescence (CF) to investigate the effect of a range of potentially stressful factors, such as light quality [7] and disease resistance [18], on outcomes such as post-harvest quality [19][20][21]. In addition, the effects of NaCl concentrations on growth and nutritional parameters have also been examined in multiple varieties of lettuce [6,8,19,22,23].…”

Image-Based High-Throughput Detection and Phenotype Evaluation Method for Multiple Lettuce Varieties

“…Lettuce is an economically important vegetable crop widely cultivated in the world, with the highest outputs in the United States, Europe, and China ( Adhikari et al, 2019 ). Rich in vitamins, carotenoids, antioxidants, and other phytonutrients ( Humphries and Khachik, 2003 ), lettuce is the most consumed leafy vegetable in salads in Europe and the United States and also one of the most commonly used vegetables in Chinese hotpot cuisine.…”

Proteomics Analysis Indicates Greater Abundance of Proteins Involved in Major Metabolic Pathways in Lactuca sativa cv. Salinas than Lactuca serriola Accession US96UC23

“…Cultivated lettuce (Lactuca sativa L.) is one of the most popular leafy green vegetables around the world, with production totaling 27 million tons in 2017 (http: //www.fao.org/faostat/, accessed 2019- [12][13][14][15][16][17][18]. It is the most important leafy green vegetable grown in the U.S., valued at $1.8 billion in California, U.S.A. in the 2018 crop year (https://www.cdfa.ca.gov/ statistics/, accessed 2019- [12][13][14][15][16][17][18]. It comes in many different shapes, sizes, and colors, and is very distinct in phenotype from wild lettuce.…”

“…[8,9] Wild lettuce shows distinct physiological traits compared to cultivated. A large number of studies have compared cultivated and various species of wild lettuce with the goal of improving traits in cultivated lettuce, including disease resistance, [10,11] pest resistance, [12,13] salt tolerance, [14,15] drought tolerance, [5,16] heat tolerance, [17,18] and bolting resistance. [19] A number of these studies have been successful in facilitating the release of cultivars with genes from wild relatives conferring resistance to downy mildew.…”