Variation in thermotolerance of photosystem II energy trapping, intersystem electron transport, and photosystem I electron acceptor reduction for diverse cotton genotypes

Navneet Kaur; John L Snider; Andrew H Paterson; Timothy L Grey; Changying Li; Gurpreet Virk; Ved Parkash

doi:10.1016/j.plaphy.2023.107868

Variation in thermotolerance of photosystem II energy trapping, intersystem electron transport, and photosystem I electron acceptor reduction for diverse cotton genotypes

Plant Physiol Biochem. 2023 Aug:201:107868. doi: 10.1016/j.plaphy.2023.107868. Epub 2023 Jun 28.

Authors

Navneet Kaur¹, John L Snider², Andrew H Paterson³, Timothy L Grey², Changying Li⁴, Gurpreet Virk², Ved Parkash²

Affiliations

¹ Department of Crop and Soil Sciences, University of Georgia, Tifton, GA, 31794, USA. Electronic address: Navneet.Kaur@uga.edu.
² Department of Crop and Soil Sciences, University of Georgia, Tifton, GA, 31794, USA.
³ Department of Genetics, University of Georgia, Athens, GA, 30602, USA.
⁴ School of Electrical and Computer Engineering, University of Georgia, Athens, GA, 30602, USA.

PMID: 37459803
DOI: 10.1016/j.plaphy.2023.107868

Abstract

Cotton breeding programs have focused on agronomically-desirable traits. Without targeted selection for tolerance to high temperature extremes, cotton will likely be more vulnerable to environment-induced yield loss. Recently-developed methods that couple chlorophyll fluorescence induction measurements with temperature response experiments could be used to identify genotypic variation in photosynthetic thermotolerance of specific photosynthetic processes for field-grown plants. It was hypothesized that diverse cotton genotypes would differ significantly in photosynthetic thermotolerance, specific thylakoid processes would exhibit differential sensitivities to high temperature, and that the most heat tolerant process would exhibit substantial genotypic variation in thermotolerance plasticity. A two-year field experiment was conducted at Tifton and Athens, Georgia, USA. Experiments included 10 genotypes in 2020 and 11 in 2021. Photosynthetic thermotolerance for field-collected leaf samples was assessed by determining the high temperature threshold resulting in a 15% decline in photosynthetic efficiency (T₁₅) for energy trapping by photosystem II (Φ_Po), intersystem electron transport (Φ_Eo), and photosystem I end electron acceptor reduction (Φ_Ro). Significant genotypic variation in photosynthetic thermotolerance was observed, but the response was dependent on location and photosynthetic parameter assessed. Φ_Eo was substantially more heat sensitive than Φ_Po or Φ_Ro. Significant genotypic variation in thermotolerance plasticity of Φ_Eo was also observed. Identifying the weakest link in photosynthetic tolerance to high temperature will facilitate future selection efforts by focusing on the most heat-susceptible processes. Given the genotypic differences in environmental plasticity observed here, future research should evaluate genotypic variation in acclimation potential in controlled environments.

Keywords: Gossypium barbadense; Gossypium hirsutum; Photosynthesis; Thermotolerance; Thylakoid reactions.