LeafPoseNet: A low-cost, high-accuracy method for estimating flag leaf angle in wheat

Abstract

Flag leaf angle (FLANG) is one of the key traits in wheat breeding due to its impact on plant architecture, light interception, and yield potential. An image-based method of measuring FLANG in wheat would reduce the labor and error of manual measurement of this trait. We describe a method for acquiring in-field FLANG images and a lightweight deep learning model named LeafPoseNet that incorporates a spatial attention mechanism for FLANG estimation. In a test dataset with wheat varieties exhibiting diverse FLANG, LeafPoseNet achieved high accuracy in predicting the FLANG, with a mean absolute error (MAE) of 1.75°, a root mean square error (RMSE) of 2.17°, and a coefficient of determination (К?) of 0.998, significantly outperforming established models such as YOLO12x-pose, YOLO11x-pose, HigherHRNet, Lightweight-OpenPose, and LitePose. We performed phenotyping and genome-wide association study to identify the genomic regions associated with FLANG in a panel of 221 diverse bread wheat genotypes, and identified 10 quantitative trait loci. Among them, qFLANG2B.2 was found to harbor a potential causal gene, TraesCS2B01G313700, which may regulate FLANG formation by modulating brassinosteroid levels. This method provides a low-cost, high-accuracy solution for in-field phenotyping of wheat FLANG, facilitating both wheat FLANG genetic studies and ideal plant type breeding.