| Wheat is one of the major food crops in the world.It has the characteristics of wide planting range and strong adaptability to the environment.The wheat grown in China is roughly divided into spring wheat and winter wheat due to the different environments in which it is located.Heilongjiang Province is located in the alpine region,and in the past only spring wheat was grown in Heilongjiang.The breeding of Dongnongdongmai 1(Dn1)opened a new chapter of the cultivation of winter wheat in the alpine region of China,and the listing of Dongnongdongmai 2(Dn2)confirmed our confidence in winter wheat research.The overwintering physiology of winter wheat in the alpine region is different from that in Huanghuaihai area.Therefore,a detailed exploration of the physiological characteristics of winter wheat in the alpine region will help improve the selection and cultivation of cold-resistant crops.Adding the aid of mathematical modeling to physiological research can improve the prediction of certain specific abilities of crops.An accurate,stable and efficient biological prediction model can reduce a large number of tedious physiological and biochemical experimental operations.It also provides a simple and quick detection method for quickly understanding the specific quality of crops.In this study,a three-year field experiment was carried out in the alpine region of Heilongjiang Province with the strong cold-resistant winter wheat varieties(Dn1 and Dn2)and the weakly coldresistant winter wheat variety Jimai 22(J22)as experimental materials.Samples were collected during the wheat growing period,overwintering period,and rejuvenation period.A total of 24 weeks of samples were collected each year,the daily temperature and precipitation were monitored.The sampled indicators included photos of wheat plant morphology during the growth period,actual plant height in the field,leaf area,leaf inclination,number of tillers before overwintering,leaf chlorophyll content,maximum photosynthetic efficiency,actual photosynthetic efficiency of photosystem II,and photochemical quenching coefficient,non-photochemical quenching,relative electron transfer efficiency of photosystem II and leaf electrical conductivity.In addition,we also measured indexes relating to the osmotic stress ability and antioxidant capacity of winter wheat tillering nodes weekly throughout the winter period.The correlation analysis of osmotic stress and anti-oxidation ability index with temperature during the overwintering period was carried out,and the correlation analysis of the above indexes with precipitation was carried out during turning green period.Finally,we used the three-year overwintering period detection indicators to establish 5winter wheat cold resistance prediction models with 5 algorithms,fully verified each model,chose the simplest and reliable model,extracted parameters,and summarized winter wheat prediction model of winter wheat overwintering in alpine region.The main results are as follows:1.Morphological characteristics of winter wheat in the growing period before overwinteringFor winter wheat in alpine region,its morphological characteristics changed significantly with the decrease of temperature during the growth period.Compared with the weak cold-resistant variety J22,the strong cold-resistant winter wheat varieties Dn1 and Dn2 showed reduced leaf angle and plant height in the third week.As the temperature decreases,the plant type showed obvious creeping growth.Before the overwintering period,the actual plant height of Dn1 and Dn2 was less than 10 cm,and the average leaf inclination was between 20 and 30°;on the other hand,In the same growth period,winter wheat varieties with strong cold resistance showed a faster growth rate,sped up the tillering of wheat,and made the number of tillers and leaf area significantly higher than those with weak cold resistance,however,the growth rate was significantly affected by temperature in different years.In the third year of this experiment,the continuous low temperature during the growing period caused a significant decrease in the number of tillers and leaf area of winter wheat.2.Photosynthetic capacity of winter wheat in the growth period before overwinteringWith the decrease of temperature,the photosynthetic capacity of wheat gradually declined,and the difference between varieties was not significant;Fv/Fm could be maintained at a constant level during the first 9 weeks of growth,indicating that the photosynthetic system of winter wheat was not significantly damaged at this time.However,as the temperature decreases,the actual photosynthetic efficiency and q P of Y(?)showed a gradual decline,especially after the 7th week of each year;NPQ increased first and then decreased with the decrease of temperature,and also changed significantly after the 7th week;ETR showed a gradual decrease with the decrease of temperature,and it could drop to about 10 in the 9th week before the overwintering period,indicating that the photosynthesis capacity of winter wheat was very weak at this time;After entering the overwintering period in the 10 th week,the relative electrical conductivity of the leaves began to rise,indicating that the leaves were under low temperature stress.On the other hand,based on the accumulation of osmotic stress substances,we speculated that the ability of winter wheat with strong cold resistance in the dark reaction stage was higher than that of winter wheat with weak cold resistance.3.The ability of winter wheat to resist osmotic stressThe ability of winter wheat to resist osmotic stress during the overwintering process in the alpine region is particularly important.During the growth period before overwintering,as the temperature gradually decreases,winter wheat tillering nodes gradually accumulated Pro and soluble sugars,and gradually reduced the plant water content.J22 reduced the water content to 75-80% before overwintering,two strong resistance to cold winter Wheat varieties dropped to about70%;the content of Pro and soluble sugars were maintained at a high level during the whole wintering period,and the strong cold-resistant winter wheat varieties were significantly higher than J22,and the content was higher with lower ambient temperature.In addition,in the overwintering period,a higher cytosolic concentration could reduce cell icing damage;in turning green period,the faster temperature rise and the greater spring breeze,the soil moisture content decreased rapidly,to lead to spring droughts.Dn1 and Dn2 had stronger water retention capacity and resistance to spring drought.4.Antioxidant ability of winter wheatDuring the overwintering process of winter wheat in the alpine region,the antioxidant system maintained a relatively high level.During the growth period,the activity of antioxidant enzymes gradually increased with the decrease of temperature.SOD and POD changed obviously,and CAT maintained basically at the same level.During the wintering period,the antioxidant enzymes activity fluctuated with temperature changes,but it always maintained a higher level.The activity of SOD fluctuated more obviously,and the activity of POD and CAT was relatively stable;During turning green period,SOD activity at the tillering node of winter wheat was significantly positively correlated with precipitation,while the correlation between activity of POD and CAT and precipitation was not obvious.5.Winter wheat overwintering period cold resistance prediction modelIn this study,5 algorithms(logistic regression algorithm,support vector machine algorithm,decision tree algorithm,random forest algorithm and gradient boosting decision tree algorithm)were used to model and analyze the winter wheat winter hardiness prediction ability.The model was evaluated through the ROC curve.Only the AUC value of the decision tree model was equal to 0.9,and the AUC values of other models were greater than or equal to 0.95,indicating that the model had a better effect;finally,we chose a logic that was relatively simple and accurate Regression model,and extracted each index parameter,determined that the cutoff value was 0.59.For the first time,a prediction model of winter wheat overwintering period in the alpine region was established.Through the above experiments,the morphological changes,photosynthesis capacity,osmotic stress and anti-oxidative stress ability of winter wheat during the overwintering process in high-cold areas were investigated in detail,and finally a prediction model for winter wheat overwintering in high-cold areas was established for the future.Screening new varieties of winter wheat in high-cold areas and predicting the re-green conditions of winter wheat in different years provide a convenient and quick way to predict. |
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