WinRoots: A High-Throughput Cultivation and Phenotyping System for Plant Phenomics Studies Under Soil Stress
Stress due to soil composition, such as salinity, heavy metals, and nutrient deficiency, is a primary cause for crop yield reduction. Crop soil stress tolerance is a complex trait that involves the regulation of a variety of genetic and non-genetic factors such as plant morphology, metabolism, and gene regulatory networks. Traditional crop phenotyping is generally carried out in the field, which is time-consuming and labor-intensive, suffers from low throughput, and can routinely be affected by natural environmental factors beyond the control of the researcher. Under such conditions, it is hard to obtain highly accurate phenotypic data to meet the requirements of phenomics studies. In past decades, several HTP (high-throughput phenotyping) platforms have been developed for use in the field or under controlled conditions. But their operation and maintenance costs are extremely high. In addition, research aimed at crop phenotyping usually focuses on the aboveground parts of plants while the acquisition of data from root morphology is much more limited. Roots, however, are the major route for water and nutrient uptake in plants, and they may also serve as storage organs for carbohydrates, as well as the direct sensing organ of soil stress. Root morphology and root physiological functions change under soil stress. Therefore, phenotyping roots is an integral part of studying the plant phenome under soil stress conditions. Existing crop phenotyping platforms cannot fully meet the specific needs of phenomics studies of plant response to soil stress in terms of throughput, environmental controllability, or root phenotypic acquisition.
Based on this, in the attached article, a group of Chinese scientists from School of Life Sciences, Shandong University and Weifang Academy of Agriculture Sciences describe the recently developed WinRoots platform, a high-throughput plant cultivation and phenotyping system for plants grown in a soil matrix. They phenotyped soybean (Glycine max) plants exposed to salt stress as a proof of concept and demonstrated the uniformity and controllability of soil stress conditions and the high throughput of the WinRoots system. And they developed optimized salt stress conditions and phenotypic indices suitable for high-throughput phenotyping of salt tolerance in soybean. In addition, a high-throughput multiple-phenotypic analysis indicates that the cotyledon character can serve as a useful non-destructive indicator of the whole-seedling salt tolerance in soybean.
In this research, A Canon EOS 700D digital camera and a Resonon PIKA L hyperspectral imager were used to collect RGB (in raw format) and hyperspectral images, respectively. The camera was positioned from a slidable horizontal rail 1.5 m above the plant material. The images of soybean canopy (overhead shot) and of the whole seedlings (side shot) were collected every day. On the 9th day of cultivation, images were taken of detached leaves with three replicates for each cultivar.
The WinRoots system: a soil-based, high-throughput plant culture platform for phenotyping roots and whole plants. Schematic representation of the usage of the system.
[Results]:
Correlation analysis between salt stress-related traits. (A) Correlation matrix between salt stress-related traits. Data were collected from 10 seedlings of 146 different cultivars grown for 10 days under mock or 175 mM NaCl treatment. (B) Regression curve between the predicted value and observed value. The prediction was performed in a new group including 32 cultivars.
Agglomerative hierarchical clustering of salt stress-related traits in soybean (A) The profile plot of the agglomerative hierarchical clustering of salt stress-related traits in soybean. Analysis was performed with the standardized indices. (B) Phenotypes of the representative cultivar for Cluster 1 and Cluster 2. Images of the whole seedlings from the soybean cultivars grown in WinRoots for 10 days. Bar, 5 cm in the whole-seedling images. Bar, 5 mm in the seeds images. (C) The comparison between the indices of Cluster 1 and Cluster 2
[Conclusion]:
In conclusion, the WinRoots system provides uniform and controllable soil stress conditions for seedling growth, can be used for high-throughput cultivation and phenotyping under soil stress, and helps provide accurate and diverse soil stress-related phenotypic data. WinRoots therefore offers an improved method to analyzing complex traits such as soil stress.