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Key message <p><b>This review provides a comprehensive mechanistic framework for rice adaptation to low-light stress, integrating morpho-physiological adjustments and biochemical plasticity with the phytochrome-PIF signalling network to guide molecular breeding of light-resilient cultivars.</b></p> Abstract <p>Low-light stress (LLS), defined as photosynthetically active radiation below 600&#xa0;μmol&#xa0;m<sup>−2</sup>&#xa0;s<sup>−1</sup>, is an increasingly important constraint on rice productivity in monsoon-dominated agroecosystems, where persistent cloud cover, dense planting, and atmospheric pollution markedly reduce light availability. Under natural field conditions, pollution-derived seasonal LLS causes yield losses of 10–20% in peri-urban environments; under controlled shade-net simulations, yield losses reach 30–55% during the reproductive stage across diverse <i>indica</i> genotypes, representing upper-bound physiological estimates rather than typical field outcomes. This review synthesises recent advances in understanding rice adaptation to LLS by integrating morpho-physiological, biochemical and molecular regulatory mechanisms with breeding-oriented perspectives. LLS induces a pronounced shade-avoidance syndrome characterised by excessive internode elongation, reduced root growth and increased lodging susceptibility, largely driven by altered assimilate partitioning. At the physiological and biochemical levels, LLS compromises photosynthetic efficiency through chloroplast ultra-structural remodelling, enhanced granal stacking, reduced Rubisco abundance and decreased photosystem II (PSII) reaction centre density, resulting in photochemical imbalance. Reproductive development is particularly sensitive to LLS, leading to delayed flowering, reduced pollen viability, impaired grain filling and increased grain chalkiness. Mechanistically, LLS tolerance is governed by stringent regulation of phytochrome-mediated signalling, wherein tolerant genotypes maintain higher PHYA and PHYB activity to restrain excessive shade responses. This regulation involves activation of positive regulators such as <i>HY5</i> and <i>HFR1</i>, repression of PHYTOCHROME-INTERACTING FACTORS, and fine-tuning by microRNAs and epigenetic signatures, whereas susceptible genotypes exhibit unchecked PIF accumulation and hormonal imbalance. From a translational standpoint, this review highlights tolerant donors such as Swarnaprabha and consolidates evidence for key quantitative trait loci and stable genomic hotspots associated with yield stability under LLS. Collectively, these insights provide a mechanistic framework to accelerate the development of rice cultivars resilient to light-limited environments.</p>

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Rice adaptation to low-light stress: integrating morpho-physiology, biochemical plasticity, signalling networks and molecular breeding strategies

  • 期刊论文

  • 发表日期：

    2026年5月15日

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  • Darshan Panda,
  • Soumya Mohanty,
  • Swagatika Das,
  • Baneeta Mishra,
  • Ranjan Kumar Jena,
  • Rameswar Prasad Sah,
  • Awadhesh Kumar,
  • BN Devanna,
  • C. Anil Kumar,
  • KR Reshmi Raj,
  • Sharat Kumar Pradhan,
  • Sanghamitra Samantaray,
  • Mirza Jaynul Baig,
  • Lambodar Behera

摘要

Key message

This review provides a comprehensive mechanistic framework for rice adaptation to low-light stress, integrating morpho-physiological adjustments and biochemical plasticity with the phytochrome-PIF signalling network to guide molecular breeding of light-resilient cultivars.

Abstract

Low-light stress (LLS), defined as photosynthetically active radiation below 600 μmol m−2 s−1, is an increasingly important constraint on rice productivity in monsoon-dominated agroecosystems, where persistent cloud cover, dense planting, and atmospheric pollution markedly reduce light availability. Under natural field conditions, pollution-derived seasonal LLS causes yield losses of 10–20% in peri-urban environments; under controlled shade-net simulations, yield losses reach 30–55% during the reproductive stage across diverse indica genotypes, representing upper-bound physiological estimates rather than typical field outcomes. This review synthesises recent advances in understanding rice adaptation to LLS by integrating morpho-physiological, biochemical and molecular regulatory mechanisms with breeding-oriented perspectives. LLS induces a pronounced shade-avoidance syndrome characterised by excessive internode elongation, reduced root growth and increased lodging susceptibility, largely driven by altered assimilate partitioning. At the physiological and biochemical levels, LLS compromises photosynthetic efficiency through chloroplast ultra-structural remodelling, enhanced granal stacking, reduced Rubisco abundance and decreased photosystem II (PSII) reaction centre density, resulting in photochemical imbalance. Reproductive development is particularly sensitive to LLS, leading to delayed flowering, reduced pollen viability, impaired grain filling and increased grain chalkiness. Mechanistically, LLS tolerance is governed by stringent regulation of phytochrome-mediated signalling, wherein tolerant genotypes maintain higher PHYA and PHYB activity to restrain excessive shade responses. This regulation involves activation of positive regulators such as HY5 and HFR1, repression of PHYTOCHROME-INTERACTING FACTORS, and fine-tuning by microRNAs and epigenetic signatures, whereas susceptible genotypes exhibit unchecked PIF accumulation and hormonal imbalance. From a translational standpoint, this review highlights tolerant donors such as Swarnaprabha and consolidates evidence for key quantitative trait loci and stable genomic hotspots associated with yield stability under LLS. Collectively, these insights provide a mechanistic framework to accelerate the development of rice cultivars resilient to light-limited environments.