The Influence Of Different Regional Climatic Conditions On Grain Color And Germination Vigor Of Rapeseed

Rape is an important oil crop in the world,and rapeseed seed color and germination vigor are important indicators reflecting rapeseed quality and rapeseed yield.Regional climatic conditions and varieties are the main factors limiting the color and germination vigor of rapeseed.Exploring the influence of regional climatic conditions and varieties on the color and germination vigor of rapeseed can provide a theoretical basis for achieving high quality and high yield of rapeseed.The 24 Brassica napus varieties selected in this study,In the Yangtze River basin（Chengdu,Chongqing,Hanzhong,Sanyuan,Jingzhou,Wuhan,Yangzhou,Hangzhou）8 experimental sites planting,through the image acquisition device and the artificial climate chamber,the various color parameters and germination indexes of rapeseed in different varieties and different regions were determined,evaluation indexes for grain color and germination vigor were determined,the difference of grain color and germination vigor in different regions were analyzed,different types of rape varieties and suitable planting areas were selected,the relationship between different regional meteorological factors and grain color and germination vigor was explored,key meteorological factors in each growth period were identified,a classification model of grain color and germination vigor was constructed,based on this,the effects of key meteorological factors on grain color and germination vigor were further analyzed.The main conclusions of this study are as follows:（1）Under RGB and HSV color space,a single color feature value is not suitable as the index of rapeseed color.R-B and S+V-H can distinguish rapeseed seeds in different color feature combination,but the coefficient of variation of S+V-H of different color levels is generally higher than R-B.Therefore,S+V-H is determined as the index of rapeseed color depth,the smaller the S+V-H value,the darker the grain color.The coefficient of variation of each germination index is:AUC/T₅₀>the germination curve area（AUC）>half of the germination time(T₅₀)>germination potential（GE）>germination rate（GP）,and by multiple comparison,the difference between AUC/T₅₀is greater than the original four germination index,so AUC/T₅₀as the evaluation of rapeseed seed germination vigor index,the larger AUC/T₅₀the higher grain germination vigor.（2）By comparing the performance of different rapeseed varieties in different regions found,grain color and germination vigor were significantly different among different varieties,Huayouza 158,Zheyou 51 comprehensive traits showed the best performance,they belong to cultivar with deep grain color,high germination vigor,and small variation in grain color and strong adaptability,Yanyouza 3,Dadi 199 showed the worst performance,they belong to the variety with light grain color and low germination vigor and weak adaptability.There are also obvious differences in grain color and germination vitality among different regions.The varieties performed the best in Hangzhou and the worst in Chengdu.In terms of the Yangtze River basin,the upper and lower reaches of the Yangtze River are more suitable for forming rapeseed seeds with high deep germination vitality than the upper and middle reaches of the Yangtze River.Further analysis found that the climate conditions caused different regional grain color and germination vitality has obvious differences,each meteorological factor had significant effects on seed color and germination vitality（P<0.05）,among them,the daily average temperature difference,lowest temperature,average temperature are affect grain color sensitive meteorological factors,sunshine hours,average daily temperature difference,effective accumulated temperature are sensitive meteorological factors affecting germination vigor.（3）Principal component analysis revealed significant differences between samples with different grain color and germination vigor,which demonstrates the feasibility of constructing grain color and germination vigor classification models using key meteorological factors in each period.Using two machine learning algorithms:decision tree and random forest,the classification accuracy of the grain color and germination vigor classification model was 75.8%,72.4%,82.8%and 81.3%respectively on the test set,the test set is close to the classification accuracy of the out-of-bag data,so the established random forest model has better generalization ability,and the established random forest model can predict the rapeseed grain color and germination vitality by using the random forest model.（4）Using random forest feature importance analysis and partial dependence analysis found that the lowest temperature has the biggest influence on grain color,and the sum of its influence in the bud bolt period and the pod period is 0.445,the response between the grain color and the lowest temperature in different growth period,that is,with the rise of the lowest temperature,the probability of dark grain formation decreased,but in different turning points,in the bud bolt and the pod bolt turning point is 7.5℃,14.5℃respectively.Sunshine hours had the greatest impact on germination vigor,and the sum of its effects at seedling,flowering and pod stages was 0.266,and its response relationship with germination vigor was consistent in different growth stages,that is,the increase in sunshine hours was conducive to the formation of rapeseed with high germination vigor,but it no longer affects germination vigor after a certain period of sunshine,and the turning points of sunshine hours reaching saturation in different periods are 6 h,6.5 h,and10 h,respectively.The daily average temperature difference is a common meteorological factor that affects grain color and germination vigor,and it has a greater impact on grain color and germination vigor（0.259 and 0.156,respectively）.When the average daily temperature difference of seedling stage is less than 8℃,it is beneficial to the formation of both deep seed color and high germination vitality,and when the average daily temperature difference of seedling stage is greater than 9℃,it is not conducive to the formation of deep seed color and rapeseed seed with high germination vitality,when the average daily temperature difference of flowering period is within the range of 8～10℃,it is beneficial to the formation of deep grain rapeseed grains but has little impact on germination vitality,when the average daily temperature difference of flowering period is greater than 10℃,it is not conducive to the formation of rapeseed grains with high germination vitality.