Genome-wide association studies for seed thermoinhibition in lettuce reveals the interplay of seed age, color, and germination under high temperatures

Authors: Oh, Sookyung; Ahn, Ezekiel; SHI, AINONG - University Of Arkansas; Mou, Beiquan; Park, Sunchung

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2024
Publication Date: 1/3/2025
Citation: Oh, S., Ahn, E.J., Shi, A., Mou, B., Park, S. 2025. Genome-wide association studies for seed thermoinhibition in lettuce reveals the interplay of seed age, color, and germination under high temperatures. Scientific Reports. https://doi.org/10.1038/s41598-024-84197-3.
DOI: https://doi.org/10.1038/s41598-024-84197-3

Interpretive Summary: Thermoinhibition, or the suppression of seed germination by high temperatures, is a natural adaptation that helps seeds time their sprouting to ensure the best chances of survival and growth. However, this trait can cause problems for agriculture, leading to uneven and reduced germination of crops, especially during the increasingly warm growing seasons. This poses a challenge for farmers as it can significantly impact crop yields. In our study, we examined a variety of lettuce species, including wild types and those commonly cultivated. We discovered that wild lettuce, which is an ancestor of the lettuce we eat today, was less affected by high temperatures compared to the domesticated varieties. Our research also showed that older seeds and lighter-colored seeds were more likely to experience thermoinhibition. Through detailed genetic analysis, we identified candidate genes related to this trait, some of which are involved in plant hormone pathways like ethylene and ABA signaling. Additionally, we found a link between the color of the seeds and their response to heat, with darker seeds generally showing less thermoinhibition. Understanding the genetic factors behind thermoinhibition can help breeders create new lettuce varieties that are more resistant to heat. This could be particularly beneficial as global temperatures continue to rise due to climate change. By selecting for genes that reduce thermoinhibition, it might be possible to develop lettuce crops that germinate more reliably and uniformly, even in warmer conditions. This advancement could lead to improved crop yields and greater food security in regions facing increasing heat. These findings will be use by plant breeders and researchers studying temperature tolerance in plants.

Technical Abstract: Thermoinhibition, the suppression of seed germination by high temperatures, is an adaptive trait that ensures successful seedling establishment in natural environments. While beneficial for wild plants, thermoinhibition can adversely affect crop yields due to uneven and reduced germination, particularly in the face of climate change. To understand the genetic basis of thermoinhibition, we conducted a comprehensive genetic analysis of a diverse panel of Lactuca spp. accessions. Our findings revealed that L. serriola, a wild ancestor of cultivated lettuce, showed relaxed thermoinhibition response compared to cultivated lettuce, suggesting that this trait may have been positively selected during early domestication in the Mediterranean region with hot, dry summers. Additionally, we found that thermoinhibition intensified with seed age and was less pronounced in dark-colored seeds. Genome-wide association studies identified genomic regions associated with thermoinhibition, including genes involved in ethylene and ABA signaling. Interestingly, some of these regions were also linked to seed color, suggesting a potential genetic coupling between black seed color and reduced thermoinhibition. These results highlighted the complex interplay between thermoinhibition, seed color, and domestication in lettuce, indicating a complicated nature of thermoinhibition regulation. By elucidating the genetic architecture of thermoinhibition, our study provides a valuable foundation for breeding strategies aimed at enhancing lettuce resilience to climate change.