Abstract: 【Objective】Researches made by the predecessors mainly focused on the indexes of crop seedling selection, less studies were carried out in quantification of seedling index model and validation, especially reports on the study of tobacco seedling index model are rare, so in practical production of tobacco seedling, exploration and development of scientific evaluations of quantitative indicators of tobacco seedling are badly needed. The establishment of a suitable vigorous seedling index model for tobacco intensive seedling in China was established to provide a theoretical basis for the normal raising seedlings and cultivating vigorous seedlings for tobacco production.【Method】Based on traditional vigorous seedling standards, following the principle of dominant, practice and operability, 17 seedling quality indexes including the plant height, stem circumference, above-ground fresh weight, underground part fresh weight, root activity, chlorophyll, and superoxide dismutase (SOD) were determined. Fuzzy comprehensive evaluation analysis was carried, and on the basis of this analysis, correlation analysis was made on each single tobacco quality indicator and the comprehensive evaluation index. Several representative quality indicators were screened, two different types of evaluation indexes were combined, namely the relative index (two single quality indexes ratio) and the composite index (3 or above 3 single quality indexes), and correlation analysis method was used to analyze the seedling quality comprehensive evaluation index and relative index, composite index, respectively, then the typical combination evaluation indexes were screened and the seedling index model was established. Finally, the seedling index model and tobacco quality index reference frequency distribution table were grouped in a reasonable manner to map each quality index and seedling index linear relationship, and the best value range of seedling index model was obtained.【Result】The range of comprehensive evaluation indexes of tobacco seedlings quality is 0.26-0.80. The range can roundly summarize tobacco seedlings quality, quantitatively and objectively evaluating the quality of tobacco seedlings. The tobacco seedling quality is divided into four levels through the total value of frequency curve method, the range of 0.71-0.80 is the optimal level for seedlings, that of 0.62-0.70 is for the sound seedlings, that of 0.41-0.61 is for the secondary seedlings, and that of 0.26-0.40 is for the weak seedlings. Relative index contains less information. Relative index can not roundly summarize tobacco seedlings quality. However, the composite index constituting multiple agronomic characters is stable, and can roundly summarize tobacco seedlings quality, and the correlation coefficient of (stem girth/plant height)×total fresh weight×10 composite index with comprehensive evaluation indexes is very significant, which can be used as the vigorous seedling index model for evaluating tobacco seedlings quality. The relationship analysis of 17 tobacco quality indexes and seedling evaluation index (stem girth/plant height)×total fresh weight×10 showed that when (stem girth/plant height)×total fresh weight×10 is in the range of 28.57-37.05, tobacco seedlings are strong, root develops well. Through field tests and verification, (stem girth/plant height)×total fresh weight×10 is 28.57-37.05, a range of rapid growth and development of tobacco plant, strong growth potential in the field, the root system is active for absorption of soil moisture and nutrients, the photosynthetic reaction is active, adverse resistance is strong, the flue-cured tobacco leaves quality is good, and the economic benefit is high.【Conclusion】The vigorous seedling indexes model (stem girth/plant height)×total fresh weight×10 can scientifically evaluate tobacco seedlings overall quality, comprehensively describe the tobacco seedling quality indexes. It is simple and convenient in application. Field experiments showed that when the numerical range takes 28.57-37.05, the tobacco seedlings quality indexes reached the maximum values, tobacco seedlings survive quickly and the survive rate was high after transplanting, the comprehensive quality of tobacco plants was good in the growth period, the flue-cured leaves have considerable economic values, and the chemical quality is good.

Key words: tobacco , seedling , vigorous seedling indexes , fuzzy comprehensive evaluation