The continents including Oceania, Europe, Asia, America, and Africa are determined by the location of the main authors’ research institute.
The sensor types are classified according to the electromagnetic spectrum from short wavelength to long wavelength, including CT, RGB, MS, HS, Flu, SIF, LIF, Thermal, LiDAR, and SAR.
The platforms are grouped into three categories, including Ground-based, Airborne, and Spaceborne, referring to Jin et al. (2021). In addition, considering that many studies involve more than one type of sensor and platform, we have included new categories that are multi-sensors and multi-platforms. Some sensors only appear in very few articles, which we classify as “Others”, such as LED light wavelengths (Huang et al., 2020).
The spatial scales include Cell/tissue, Organ, Individual, Canopy, Landscape, and Global. Considering that organs are the research scale of most concern in breeding practice, the organ level was further classified into specific organ types including Root, Stem, Leaf, Flower/panicle/head, Fruit, Seed, and Multi-organs. The Multi-organs means a study contains multiple organs.
The working environments include outdoor, indoor, and both according to the data collection conditions, where “both” means a study is implemented in both indoor and outdoor environments.
The temporal scales include Single time, Diurnal, Seasonal, and Inter-annual according to the interval between data acquisition. Single time represents data collected only one time. Diurnal means data is collected multiple times within a day. Seasonal means data is collected multiple times within a year. Inter-annual represents data collected over multiple years.
The research fields include four popular areas of grass, forestry, horticulture, agriculture, multi-fields, and others. Multi-fields represent a study involves with more than one of the four interested fields (i.e., grass, forestry, horticulture, agriculture), while others represent a study that involves none of the four interested fields. Furthermore, considering the majority of phenotypic studies were in agriculture, it was further subdivided into various crop types, including Wheat, Maize, Rice, Grape, Soybean, Cotton, Tomato, Barley, Sorghum, and Sugarcane.
The trait classes include Structural, Physiological, Performance-related, and Multi-Traits according to Dhondt et al. (2013). In addition, this study added a multi-traits class that represents a study that involves more than one kind of trait.
The multi-omics studies include P-E, P-G, and P-E-G where P, E, and G represent phenomics, environment, and genomics, respectively. Notably, an article can be categorized into different types using different category rules based on study aims. For example, an article can be classified as a root study according to organ types (Spatial scale category), and it also can be classified as an indoor study according to the study environment (Working environment category).”
Jin, S., Sun, X., Wu, F., Su, Y., Li, Y., Song, S., Xu, K., Ma, Q., Baret, F., Jiang, D., Ding, Y., & Guo, Q. (2021). Lidar sheds new light on plant phenomics for plant breeding and management: Recent advances and future prospects. ISPRS Journal of Photogrammetry and Remote Sensing, 171, 202-223
Huang, L., Xiao, Y., Ran, J., Wei, L., Li, Z., Li, Y., Zhang, X., Liao, L., Wang, D., Zhao, X., Xiao, Q., & Guo, Y. (2020). Drought tolerance of faba bean (Vicia faba L.) can be improved by specific LED light wavelengths. Photosynthetica, 58, 1-13 Dhondt, S., Wuyts, N., & Inze, D. (2013). Cell to whole-plant phenotyping: the best is yet to come. Trends in Plant Science, 18, 428-439