July 3, 2025

Assessment of pepper immunity to Phytophthora capsici and potato virus Y. - Credit: Horticulture Research
 

As climate change fuels extreme weather events, ensuring crops can maintain disease resistance under shifting temperatures is critical. A recent study delved into how pepper plants respond immunologically to heat stress, focusing on their ability to resist two major pathogens. By introducing a new framework with nine quantitative indicators, the researchers mapped how robust—or fragile—immune responses were across a genetically diverse pepper population. Their results reveal that immunity isn't just about being strong—it's also about staying consistent when the environment changes, offering key insights for breeding resilient, climate-smart crops.

Plants constantly battle a barrage of environmental stressors, from rising heat to invading pathogens. While genetic resistance offers a defense shield, its effectiveness often depends on external conditions—especially temperature. Inconsistent immune responses raise serious concerns for future crop reliability, particularly in the face of global warming. Surprisingly, most research has ignored how immunity holds up across different environments. The concept of “robustness”—the stability of a trait under stress—has remained underexplored in plant immunity. Due to these gaps in understanding, there is a pressing need to investigate how plant immune traits endure environmental fluctuations and to develop ways to measure and improve this robustness.

A research team from INRAE and affiliated institutions has taken a closer look at how temperature swings affect pepper plant immunity. Published (DOI: 10.1093/hr/uhae239) on August 21, 2024, in Horticulture Research, the study evaluated 163 accessions of Capsicum annuum exposed to two major pathogens—Phytophthora capsici and potato virus Y (PVY)—under two temperature regimes. The researchers developed nine new indicators to assess the robustness of immunity across conditions. Their work not only maps the immune landscape of pepper varieties but also lays the foundation for selecting climate-resilient crops.

The study simulated real-world climate stress by growing pepper plants under standard and elevated temperatures, then infecting them with either P. capsici or PVY. The immune response varied sharply: high temperatures worsened susceptibility to P. capsici but improved resistance to PVY. To capture how immunity held up across conditions, the team introduced nine "robustness" metrics—some measuring stability in average resistance, others in variability across individuals.

They discovered that robustness of mean and robustness of variation are distinct yet complementary traits. Some pepper lines showed remarkable consistency across both environments, while others were more vulnerable to change. Among the robustness metrics, those measuring changes in average immunity had the highest heritability—meaning they're prime candidates for use in breeding programs. A key takeaway: higher immunity often aligned with higher robustness, but this link was pathogen-specific. This underscores the complexity of breeding for multi-pathogen resilience and highlights the importance of tailoring strategies for each threat. By pinpointing genotypes that perform well under stress, the study opens new pathways for breeding crops that can defend themselves—not just now, but in the unpredictable climates of tomorrow.

“Our results reveal that immunity is not a one-size-fits-all trait,” said lead author William Billaud. “Plants may react very differently to temperature changes depending on the pathogen. By identifying which genotypes maintain strong defenses across conditions, we give breeders powerful tools to develop crops that are both resilient and sustainable. This could play a crucial role in reducing pesticide dependence and stabilizing yields in a warming world.”

The study's implications extend far beyond pepper. With Europe moving toward new regulations requiring crop varieties to demonstrate sustainable cultivation value, the ability to quantify trait robustness is becoming increasingly important. These nine metrics offer breeders and regulators a practical toolkit for assessing stability under environmental stress. Going forward, applying this framework across different crops and climate conditions could transform how we define and breed climate-resilient plants. By identifying pepper accessions that combine strong immunity with environmental stability, the researchers offer valuable starting points for next-generation breeding programs aimed at thriving in a climate-challenged future.

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References

DOI

10.1093/hr/uhae239

Original Source URL

https://doi.org/10.1093/hr/uhae239

Funding information

This work was also partly supported by the Horizon Europe Program, project “Promoting Plant Genetic Resource Community for Europe” (PRO-GRACE project number no. 101094738). William Billaud received a scholarship from the Structure Fédérative de Recherche (SFR)

About Horticulture Research

Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.

Website: http://english.njau.edu.cn/

Published: July 3, 2025