Abstract
A reasonable plant type is an essential factor for improving canopy structure, ensuring a reasonable expansion of the leaf area index and obtaining a high-quality spatial distribution of light. It is of great significance in promoting effective selection of the ecological breeding index and production practices for maize. In this study, a method for calculating the phenotypic traits of the maize canopy in three-dimensional (3D) space was proposed, focusing on the problems existing in traditional measurement methods in maize morphological structure research, such as their complex procedures and relatively large error margins. Specifically, the whole maize plant was first scanned with a FastSCAN hand-held scanner to obtain 3D point cloud data for maize. Subsequently, the raw point clouds were simplified by the grid method, and the effect of noise on the quality of the point clouds in maize canopies was further denoised by bilateral filtering. In the last step, the 3D structure of the maize canopy was reconstructed. In accordance with the 3D reconstruction of the maize canopy, the phenotypic traits of the maize canopy, such as plant height, stem diameter and canopy breadth, were calculated by means of a fitting sphere and a fitting cylinder. Thereafter, multiple regression analysis was carried out, focusing on the calculated data and the actual measured data to verify the accuracy of the calculation method proposed in this study. The corresponding results showed that the calculated values of plant height, stem diameter and plant width based on 3D scanning were highly correlated with the actual measured data, and the determinant coefficients R2 were 0.9807, 0.8907 and 0.9562, respectively. In summary, the method proposed in this study can accurately measure the phenotypic traits of maize. Significantly, these research findings provide technical support for further research on the phenotypic traits of other crops and on variety breeding.
Highlights
The selection and breeding of excellent maize varieties has attracted extensive international attention [1]
Model of the whole maize plant, it it was necessary that the reference body (consisting of a transmitter and was necessary to ensure that the electromagnetic reference body (consisting of a transmitter and a was necessary to ensure that the electromagnetic reference body andthe the maizeplant plant were relativelystatic static stateand andthat that neitherside side move during during receiver) and maize were ininaarelatively state neither could move receiver) and the maize plant were in a relatively static state and that neither side could moveofduring the scanning scanning quality, the the hand-held device (Wand) and the maize the scanning process
Manual measurement of the actual phenotypic traits was affected by subjective factors related to the surveyor and by the external environment
Summary
The selection and breeding of excellent maize varieties has attracted extensive international attention [1]. Many influential research centers, such as the International Maize and Wheat. Improvement Center (CIMMYT) [2] and the International Center for Agricultural Research in the Dry. Areas (ICARDA) [3] have been working on genetic diversity and cultivation of maize plants. Maize is one of the most important food crops in China, as well as one of the most important industrial raw materials and economic crops. Deep processing of maize can be widely applied in food, medicine, bioenergy and more than 20 other industries. The development of the Chinese maize industry is inseparable from maize breeding. With the increases in drought, diseases and insect pests, Sensors 2019, 19, 1201; doi:10.3390/s19051201 www.mdpi.com/journal/sensors
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