Plant Gene and Trait 2025, Vol.16, No.4, 152-161 http://genbreedpublisher.com/index.php/pgt 157 plants and the stable performance of leaves (Han et al., 2022; Feng et al., 2024). Soil with abundant organic matter and moderate pH can help increase yield and quality, while soil with good water retention can better resist drought and high temperature (Wen et al., 2021; Giannitsopoulos et al., 2023). 7.3 Interactions between rainfall patterns and heatwave timing The intensity and distribution time of rainfall, as well as when heat waves arrive, have a significant impact on the moisture state and nutrient loss of tea trees. If it rains heavily, the nitrogen in the sloping tea garden is prone to be washed away, which will affect the yield and tea quality (Ye et al., 2024). During heat waves, if there is not enough rainfall, tea trees are also prone to water shortage, and their leaves are likely to be damaged. Simulation experiments have found that rainfall, soil water-conducting capacity and fertilization interact with each other, all of which affect nitrogen loss and tea yield. By rationally arranging fertilization and watering, the adverse effects brought by extreme weather on tea gardens can be reduced (Ahmed et al., 2019). 8 Technologies for Field Monitoring and Evaluation 8.1 Remote sensing and non-invasive monitoring tools Nowadays, with remote sensing and hyperspectral imaging technology, it is possible to monitor the heat tolerance of tea plants more quickly and easily. By taking hyperspectral images of tea tree leaves and combining them with physiological indicators such as malondialdehyde, soluble sugar, and polyphenols, tea trees with strong heat resistance can be quickly screened out. If these image data are combined with machine learning methods (such as support vector machine, random forest, partial least squares regression), accurate prediction of the stress resistance of tea plants can be made, and large-scale field detection can be carried out without damaging the leaves (Chen et al., 2022). 8.2 Field phenotyping instruments Some commonly used tools for measuring the heat resistance of tea plants in the field include portable chlorophyll meters, photosynthesis measurement instruments, biochemical detection equipment and automatic sampling systems. These instruments can help us understand in real time the key physiological responses such as chlorophyll level, water retention capacity and antioxidant enzyme activity of tea plants under high temperature, and thereby determine whether a variety is heat-resistant (Rahimi et al., 2018; Huang et al., 2024). Furthermore, if transcriptome and metabolome analyses are added, the internal regulatory mechanisms of heat-tolerant tea plants can be further understood at the molecular level, providing more data support for the analysis of field performance (Shen et al., 2019). 8.3 AI- and data-based models for adaptive trait evaluation Artificial intelligence and data models are also very useful in the selection and breeding of tea trees. By integrating data from different sources such as high-throughput phenotypes, transcriptomes, and metabolomics, we can establish predictive models to more accurately determine which tea trees are more heat-tolerant. For instance, Tea-DTC is an AI model that uses hyperspectral data to predict the drought resistance of Tea plants and performs well (Chen et al., 2022). In addition, the combined analysis of transcriptome and metabolome also revealed some key regulatory pathways and gene networks at the molecular level of heat-tolerant varieties, providing a lot of valuable information for AI models (Seth et al., 2021; Huang et al., 2024). 9 Case Study: Field Performance of Heat-Tolerant Tea Varieties in Mississippi and Zhejiang 9.1 Regional background and ecological conditions In subtropical humid climate zones like Mississippi in the United States, the hot summer weather and strong sunlight are the main problems affecting the growth of tea trees and the health of their leaves. It is often hot and rainy in summer here, and sometimes low temperature occurs in winter. Therefore, tea trees must have a stronger heat tolerance to adapt (Zhang et al., 2020; Zhang et al., 2022). Some tea-growing areas in China, such as Zhejiang, also encounter the situation of continuous high temperatures in summer, which will affect the output and quality of tea (Yang et al., 2023).
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