Study On Drought And Saline-alkali Resistance Of 16 Alfalfa Varieties And Comprehensive Evaluation

Drought and soil salinization are two major obstacles to plant growth and development.The study aims to explore the morphological changes and physiological response mechanism of alfalfa seed germination and seedlings under drought and salinity stress,and the differences of drought and salinity tolerance among alfalfa varieties.Sixteen alfalfa cultivars were selected to study the effects of drought and saline-alkali stress on seed germination,seedling morphology and physiology by dish dipping method and pot method.The drought and saline-alkali tolerance of 16 alfalfa cultivars were evaluated comprehensively by subordinate function method.The results showed that:1)The drought tolerance of alfalfa varieties was different in germination stage.Through the cluster analysis of seed germination indexes,the drought resistance of 16alfalfa varieties can be divided into 4 categories.Class I include such varieties with strong drought-resistance as GongNong No.5,Gibraltar,Surprise,WL343HQ,Caribou,Dryland,MT4015,Algonquin.Class II was a medium drought resistant variety including GongNong No.1,Graze7,Spyder,Golden Empress.Class III was a weak drought resistance variety including 3010,Graze2,Instinct.Class IV was a drought sensitive variety only including a Forerunner.2)The analysis of the response of morphological and physiological indexes to the drought in the seedling stage by repeated drought methods showed that plant height,leaf area,leaf length and width decreased with increasing drought stress.Pro and soluble sugar content was positively correlated with drought resistance.Root activity,MDA and chlorophyll content were negatively correlated with drought resistance.Through the correlation principal component analysis,combined with the standard deviation weighting,the correlation between the measured index and drought resistance was ranked as Pro>root activity>MDA>plant height>chlorophyll>leaf length>leaf area>soluble sugar content>leaf width.3)The principal component analysis and adapting subordinate function method were used to comprehensively evaluate the drought resistance of 16 Species of alfalfa.The drought resistance of 16 alfalfa varieties was Gibraltar>MT4015>Golden Empress>WL343HQ>Dryland>Forerunner>Graze7>Instinct>Gong Nong No.1>Surprise>Graze2>3010>GongNong No.5>Algonquin>Caribou>Spyder.4)The Na₂CO₃ and NaHCO₃ mixed saline solution were used to seed stress treatment.According to the cluster analysis of the germination indexes,the salt tolerance of 16 alfalfa varieties was divided into three categories.Class I was strong salt-alkaline tolerance variety including WL343HQ,Golden Empress,Gibraltar,Surprise and GongNong No.1;Class II refer to moderate salt-alkali tolerance variety including Graze7,Algonquin and Instinct;Class III was weak saline-tolerant variety including GongNong No.5,Dryland,Spyder,Forerunner,MT4015,Algonquin,Graze2 and 3010.Class III include such varieties with weak saline-tolerant as GongNong No.5,Dryland,Spyder,Forerunner,MT4015,Algonquin,Graze2 and3010.5)In the experiment,the mixed saline-alkali of Na₂CO₃ and NaHCO₃significantly inhibited the growth and development of Alfalfa seedlings.Under T4concentration stress,plant height and leaf area decreased significantly compared with the control,and the Pro,soluble sugar content and MDA increased with stress.As the degree increases,the root activity and chlorophyll content decrease significantly.6)Through the weighting method of standard deviation,the comprehensive evaluation of salt-alkali resistance in seedling stages,the salt-alkali tolerance was in the order of Spyder>Graze2>Dryland>Golden Empress>3010>GongNong No.1>WL343HQ>Graze7>Surprise>Algonquin>Caribou>MT4014>Instinct>Foreru nner>GongNong No.5>Gibraltar.