title: Lettuce flavonoids screening and phenotyping by chlorophyll fluorescence excitation ratio.
abstract: Environmentally induced variation and the genotypic differences in flavonoid and phenolic content in lettuce can be reliably detected using the appropriate parameters derived from the records of rapid non-invasive fluorescence technique. The chlorophyll fluorescence excitation ratio method was designed as a rapid and non-invasive tool to estimate the content of UV-absorbing phenolic compounds in plants. Using this technique, we have assessed the dynamics of accumulation of flavonoids related to developmental changes and environmental effects. Moreover, we have tested appropriateness of the method to identify the genotypic differences and fluctuations in total phenolics and flavonoid content in lettuce. Six green and two red genotypes of lettuce (Lactuca sativa L.) grown in pots were exposed to two different environments for 50 days: direct sunlight (UV-exposed) and greenhouse conditions (low UV). The indices based on the measurements of chlorophyll fluorescence after red, green and UV excitation indicated increase of the content of UV-absorbing compounds and anthocyanins in the epidermis of lettuce leaves. In similar, the biochemical analyses performed at the end of the experiment confirmed significantly higher total phenolic and flavonoid content in lettuce plants exposed to direct sun compared to greenhouse conditions and in red compared to green genotypes. As the correlation between the standard fluorescence indices and the biochemical records was negatively influenced by the presence of red genotypes, we proposed the use of a new parameter named Modified Flavonoid Index (MFI) taking into an account both absorbance changes due to flavonol and anthocyanin content, for which the correlation with flavonoid and phenolic content was relatively good. Thus, our results confirmed that the fluorescence excitation ratio method is useful for identifying the major differences in phenolic and flavonoid content in lettuce plants and it can be used for high-throughput pre-screening and phenotyping of leafy vegetables in research and breeding applications towards improvement of vegetable health effects.
authors.affiliation: Department of Plant Physiology, Slovak Agricultural University, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic.
authors.forename: Marek
authors.initials: M
authors.lastname: Zivcak
authors.affiliation: Department of Plant Physiology, Slovak Agricultural University, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic.
authors.forename: Klaudia
authors.initials: K
authors.lastname: Brückova
authors.affiliation: Agrobiotech Research Center, Slovak Agricultural University, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic.|Educational and Scientific Centre, Institute of Biology and Medicine, Taras Shevchenko National University of Kyiv, 64/13 Volodymyrska Street, Kyiv, Ukraine.
authors.forename: Oksana
authors.initials: O
authors.lastname: Sytar
authors.affiliation: Department of Plant Physiology, Slovak Agricultural University, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic. marian.brestic@uniag.sk.
authors.forename: Marian
authors.initials: M
authors.lastname: Brestic
authors.affiliation: Department of Plant Physiology, Slovak Agricultural University, Tr. A. Hlinku 2, 949 76, Nitra, Slovak Republic.
authors.forename: Katarina
authors.initials: K
authors.lastname: Olsovska
authors.affiliation: Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya Street 35, Moscow, 127276, Russia. suleyman.allakhverdiev@gmail.com.|Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia. suleyman.allakhverdiev@gmail.com.|Department of Plant Physiology, Faculty of Biology, M.V. Lomonosov Moscow State University, Leninskie Gory 1-12, Moscow, 119991, Russia. suleyman.allakhverdiev@gmail.com.|Institute of Molecular Biology and Biotechnology, Azerbaijan National Academy of Sciences, Matbuat Avenue 2a, 1073, Baku, Azerbaijan. suleyman.allakhverdiev@gmail.com.
authors.forename: Suleyman I
authors.identifier: http://orcid.org/0000-0002-0452-232X
authors.initials: SI
authors.lastname: Allakhverdiev
mesh_terms: D002734:Chlorophyll / Q000378:metabolism*; D005419:Flavonoids / Q000378:metabolism*; D018545:Lactuca / Q000378:metabolism* / Q000528:radiation effects; D010641:Phenotype; D014466:Ultraviolet Rays
chemical_list: D005419:Flavonoids; D002734:Chlorophyll
keywords: Chlorophyll fluorescence; Flavonoids; Lettuce; Phenolic; Phenotyping; UV radiation