Construction and quality evaluation of strawberry seedling index model

With the development of strawberry cultivated area in China, the demands for high-quality strawberry seedlings are increasing year by year. The research on the evaluation index of strawberry seedlings is needed to ensure the quality of the seedlings. This study aimed to establish an optimal index model of strawberry seedlings to improve the accuracy of seedlings evaluation. In this study, 320 seedlings of 'Benihoppe' strawberry seedlings growing for 40 days were taken as the materials. Based on the determination of 16 individual indicators including the growth of aboveground and underground parts, fresh weight, and dry weight, we firstly conducted the membership function corresponding to single indicator. Then the comprehensive evaluation index of strawberry seedlings was calculated using weighted fuzzy evaluation method. Furthermore, the key indicators out of the 16 indicators which were filtered out by means of the principal component analysis method were combined into different index models of strawberry seedlings. The correlation analysis between the comprehensive evaluation index and seedling index models was done and finally the optimal seedling index model was selected and verified. The results showed that there were significant differences in 16 indices of 320 randomly selected strawberry seedlings. The comprehensive evaluation index of strawberry seedlings was in the range of 0.165-0.817, indicating that the comprehensive evaluation index could totally reflect the quality of seedlings and could be used as the evaluation basis. The 16 individual indices of strawberry seedlings were classified into three principal components, including aboveground related indicators, underground related indicators, and the pigment indicators. The cumulative contribution rate of three principal components was 79.7%. Twenty-seven seedlings index models were combined by randomly selecting three indices with a large contribution value from each principal component. Five strawberry seedlings index mo-dels were selected from 27 models due to the highest correlation with the comprehensive evaluation index. Among them, the model "aboveground dry weight×root surface area×chlorophyll a" was identified as the optimal one to evaluate the quality of strawberry seedlings, due to the highest correlation with the comprehensive evaluation index. The correlation coefficient of between strong seedling index and comprehensive evaluation index in three strawberry variety 'Benihoppe', 'Kantoseika' and 'Sweet Charlie' were 0.879, 0.924, and 0.975, respectively. According to the comprehensive evaluation index, the quality of strawberry seedlings were classified into three grades: grade Ⅰ (comprehensive evaluation index ≥0.5, seedling index ≥4.0) with high-quality seedlings; grade Ⅱ (comprehensive evaluation index 0.3-0.5, seedling index 0.5-4.0) with qualified seedlings; grade Ⅲ (comprehensive evaluation index ≤0.3, seedling index ≤0.5) with weak seedlings. The results provided a theoretical basis and scientific method for the evaluation of the health status of strawberry seedlings or other fruits and vegetable seedlings.