High-Throughput Phenotyping Approach for the Evaluation of Heat Stress in Korean Ginseng (Panax ginseng Meyer) Using a Hyperspectral Reflectance Image

Eunsoo Park,Mohammad Akbar Faqeerzada,Moon S Kim,Mohammad Kamran Omari,Hyun-Kwon Suh,Insuck Baek,Yun-Soo Kim,Byoung-Kwan Cho

doi:10.3390/s21165634

Abstract

Panax ginseng has been used as a traditional medicine to strengthen human health for centuries. Over the last decade, significant agronomical progress has been made in the development of elite ginseng cultivars, increasing their production and quality. However, as one of the significant environmental factors, heat stress remains a challenge and poses a significant threat to ginseng plants’ growth and sustainable production. This study was conducted to investigate the phenotype of ginseng leaves under heat stress using hyperspectral imaging (HSI). A visible/near-infrared (Vis/NIR) and short-wave infrared (SWIR) HSI system were used to acquire hyperspectral images for normal and heat stress-exposed plants, showing their susceptibility (Chunpoong) and resistibility (Sunmyoung and Sunil). The acquired hyperspectral images were analyzed using the partial least squares-discriminant analysis (PLS-DA) technique, combining the variable importance in projection and successive projection algorithm methods. The correlation of each group was verified using linear discriminant analysis. The developed models showed 12 bands over 79.2% accuracy in Vis/NIR and 18 bands with over 98.9% accuracy at SWIR in validation data. The constructed beta-coefficient allowed the observation of the key wavebands and peaks linked to the chlorophyll, nitrogen, fatty acid, sugar and protein content regions, which differentiated normal and stressed plants. This result shows that the HSI with the PLS-DA technique significantly differentiated between the heat-stressed susceptibility and resistibility of ginseng plants with high accuracy.

Highlights

Korean ginseng (Panax ginseng Meyer) is an herbal medicine plant and it is known to have high pharmacological efficacy in its roots
AR had a larger intensity than BH and AS had a larger intensity than AR. These results indicate a possibility of distinguishing between ginseng exposure and resistance to heat stress in the short-wave infrared (SWIR) region
In order to determine ginseng plants exposed to heat stress, hyperspectral Vis/NIR and SWIR image data that could represent the physicochemical information of ginseng plants were acquired and applied to LDA and partial least squares-discriminant analysis (PLS-DA) for our prediction model

Summary

Introduction

Korean ginseng (Panax ginseng Meyer) is an herbal medicine plant and it is known to have high pharmacological efficacy in its roots. Representative pharmacological functions are known for their immune enhancement effects and fatigue recovery [1]. The ginseng plant has a maximal photosynthetic rate at about 21–25 ◦C. Photosynthetic activity decreases when the temperature rises above 25 ◦C and the quality and production decrease as the temperature rises above 30 ◦C [2]. The increase in Earth’s average temperature is becoming a threat to crop production, including ginseng production [3]. Continual exposure to high temperatures, especially during the summer, leads to physiological disorders resulting in yellowing and defoliation of ginseng plants. Yellowing and defoliation result in the deterioration of crop quality, making it difficult to recover its productivity [2]

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