A method to quantify the degree of leaf curl in nodular Chinese cabbage (Brassica pekinensis)

Chinese cabbage (Brassica pekinensis) has a wide range of cultivation and food value. As a nutrient storage organ, the nodule leaf blade directly affects the quality and economic value of the leaf-ball. Currently, research on leaf curl trait in nodulating cabbage mostly relies on manual measurement or visual inspection methods, and the degree of leaf curl lacks quantitative evaluation criteria to accurately and efficiently utilize this trait to establish a link with gene expression. To address this problem, the present study was carried out to digitize the leaf curl phenotypic characteristics of nodulating cabbage. Selection of 171 leaf samples of different varieties of cabbage at nodulation stage, and the digital evaluation indexes of leaf curl were proposed through the three-dimensional reconstruction method based on multiview images to realize the digital evaluation of anterior-posterior, left-right, and overall leaf curl. The leaf curl phenotypic pattern was obtained from the analysis: the quantitative leaf curl value was distributed between 0-100, the larger the value, the larger the degree of curl, and vice versa, the smaller the degree of curl; the anterior-posterior leaf curl and the left-right curl traits were significantly correlated. This study realized for the first time the objective and accurate quantification of the degree of curling of nodular cabbage leaves, providing an intelligent method and digital standard for the quality identification and grading classification of cabbage. It provides an effective method for subsequent research to get rid of the influence of subjective judgment and realize accurate identification.