Artificial Shading Can Adversely Affect Heat-tolerant Lettuce Growth and Taste, with Concomitant Changes in Gene Expression

Camila M.L. Alves, Hsueh-Yuan Chang, Cindy B Tong, Charlie L. Rohwer, Loren Avalos, Zata M. Vickers

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Shading has been used to produce high-quality lettuce (Lactuca sativa) in locations where production conditions are not optimal for this cool-season crop. To learn what additional benefits shading provides if heat-tolerant cultivars are used and to understand the effects of shading on growth, sensory quality, chemical content, and transcriptome profile on heat-tolerant lettuce, we grew two romaine lettuce cultivars with and without shading using 50% black shadecloth in 2018 and 2019. Shading reduced plant leaf temperatures, lettuce head fresh weights, glucose and total sugars content, and sweetness, but not bitterness, whereas it increased lettuce chlorophyll b content compared with unshaded controls. Transcriptome analyses identified genes predominantly involved in chlorophyll biosynthesis, photosynthesis, and carbohydrate metabolism as upregulated in unshaded controls compared with shaded treatments. For the tested cultivars, which were bred to withstand high growing temperatures, it may be preferable to grow them under unshaded conditions to avoid increased infrastructure costs and obtain lettuce deemed sweeter than if shaded.

Original languageEnglish (US)
Pages (from-to)45-52
Number of pages8
JournalJournal of the American Society for Horticultural Science
Issue number1
StatePublished - Jan 2022

Bibliographical note

Funding Information:
Received for publication 20 Aug. 2021. Accepted for publication 14 Oct. 2021. Published online 9 December 2021. We thank Aaron Blythe for input on research design; Doug Brinkmann, Courtney Tchida, Adam Sauve, Jessyca Martínez-Vélez, and Taylor Bush-elle for technical assistance; Juan E.A. Llorens for assistance with transcrip-tome analysis; Gary Oehlert for statistical consultation; and Dominic Petrella and Yinjie Qiu for reviewing drafts of this manuscript. Funding was provided by the U.S. Department of Agriculture (USDA) Marketing Service (grant 64436 via the Minnesota Department of Agriculture Specialty Crops Block Grant Program) and the Minnesota Experiment Station (projects MN21-043 and 18-138). The contents of this manuscript are solely the responsibility of the authors and do not necessarily represent the official views of USDA. C.B.S.T. is the corresponding author. E-mail: This is an open access article distributed under the CC BY-NC-ND license (

Publisher Copyright:
© 2022, American Society for Horticultural Science. All rights reserved.


  • Bitterness
  • Chlorophyll
  • Lactuca sativa
  • Quality
  • Sweetness
  • Transcriptome


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