Screening And Evaluation Index Of Cultivars Tolerant To Low Nitrogen And Phosphorus At Seedling Stage Of Green Onion(Allium Fistulosum L.)

Green onion(Allium fistulosum L.)is a vegetable grown all over the country and loved by the general public.Green onion is a kind of fattening crop,and due to its weak root absorption capacity,a large amount of nitrogen fertilizer and phosphate fertilizer are often invested in production in order to obtain a higher yield,which not only increases the production cost,but also leads to serious agricultural non-point source pollution and other problems.This study takes this as a starting point,and hopes to screen out Green onions with low nitrogen or phosphorus tolerance through the variety comparison test at the seedling stage,and find out scientific,reasonable and efficient identification indexes.To achieve this purpose,this study in different varieties of green onion as the experimental material,temperature control light in artificial climate chamber,the nutrient solution hydroponics,setting normal nitrogen or phosphorus concentration and low nitrogen and low phosphorus hydroponic conditions,to carry out the green onion varieties of seedling resistance to low nitrogen or phosphorus screening study,preliminary screening process seedling resistance to low nitrogen or phosphorus species,to determine the resistance to low nitrogen or phosphorus of appraisal indicators.1.Evaluation and index selection of low-nitrogen tolerant varieties in onion seedling stageIn order to screen out the low-nitrogen-tolerant varieties and determine the low-nitrogen-tolerant identification indicators,the experiment used 25 green onion varieties collected as test materials,setting two nitrogen levels of 14 mM and 2.8 mM,using the modified Hoagland’s nutrient solution Climatic room control environment,seedling cultivation,analysis plant height,root length,stem thickness,false stem length,number of leaves,fresh weight above ground,fresh weight below ground,dry weight above ground,dry weight below ground,nitrogen content above ground,roots Canopy ratio,above-ground nitrogen accumulation and above-ground nitrogen physiology efficiency changes in 14 indicators,using membership function method,principal component analysis method,cluster analysis method and stepwise regression analysis to comprehensively evaluate the characteristics of green onion seedling stage.The results showed that 7 onion varieties including "Shaocong" and "Biancong" were selected as lownitrogen-tolerant varieties;relative dry weight above ground,relative root to shoot ratio,relative fresh ground weight,relative root length,stem The coarse relative value and the relative value of aboveground nitrogen content can be used as identification indexes of low nitrogen tolerance.2.Screening of physiological and biochemical indexes of low-nitrogen tolerant varieties in onion seedling stageIn order to further screen and identify the physiological and biochemical indexes of green onion tolerance to low nitrogen,the low nitrogen tolerance variety "Shaocong" and the low nitrogen sensitivity variety "Liaocong16-12" were used as test materials,and the moderate low nitrogen tolerance variety "Zhangqiudawutong" was used as a control,The differences in nitrogen absorption and nitrogen assimilation of different low-tolerance green onion varieties under 14 mM and 2.8 mM nitrogen levels were analyzed.The results showed that the low nitrogen tolerance of "Shaocong" was significantly higher than that of "Liaocong 16-12" and "Zhangqiudawutong".Under low nitrogen,the biomass and nitrogen accumulation of "Shaocong" increased,while the biomass and nitrogen accumulation of "Liaocong 16-12" and "Zhangqiudawutong" decreased.In addition,the low nitrogen promotes the development of the root system of "Shaocong";the root system of "Liaocong 16-12" appears slender and weak under low nitrogen.Low nitrogen treatment caused the nitrate content in "Shaocong" leaves to fall more than "Zhangqiudawutong" and "Shaocong",while the soluble protein content increased.It is speculated that the nitrogen assimilation ability of "Shaocong" is stronger than that of "Liaocong 16-12".Antioxidant enzyme system under low nitrogen conditions,the reaction between different tolerance varieties is inconsistent.The activity of "Shaocong" glutamine synthetase increased,while the activity of "Liaocong16-12" decreased,indicating that "Shaocong" is stronger than "Liaocong16-12" in nitrogen assimilation.3.Evaluation and index selection of low-phosphorus tolerant varieties in onion seedling stageIn order to screen out low-phosphate-tolerant varieties,determine the indicators that can be used to identify the low-phosphate tolerance of green onions.In this experiment,the collected 24 scallion varieties were used as test materials,and two phosphorus levels of 1 mM and 0.2 mM were set,under the control of the artificial climate room(Day time 12 hours,temperature is 25±1℃;Dark time 12 hours,the temperature is 18±1℃),seedling cultivation,analysis of the plant height,root length,stem thickness,false stem length,leaves Number,fresh weight above ground,fresh weight below ground,dry weight above ground,dry weight below ground,phosphorus content above ground,root-to-root ratio,phosphorus accumulation above ground,physiological efficiency of above ground phosphorus total 14 indicators Changes.Subordinate function method,principal component analysis method,cluster analysis method and stepwise regression analysis were used to comprehensively evaluate the resistance of green onions to low phosphorus.The results showed that "Jicong 1" was selected as a low-phosphate-tolerant variety;relative dry root weight,relative fresh root weight,relative root-to-root ratio,relative leaf length,relative aerial fresh weight,and stem thickness relative The value can be used as the identification index of the low onion tolerance of green onions at the seedling stage.