Effect Of Drought-hardening On Yield And Quality Of Alfalfa Under Water Stress

In the current situation of extreme water scarcity in agriculture,selection and breeding of alfalfa（Medicago sativa L.）varieties with stable and high yield under drought conditions is an urgent problem in the development of animal husbandry.In this experiment,we investigated whether the drought tolerance of alfalfa could be improved by Drought-hardening and analyzed the change pattern of its yield and quality after Drought-hardening.In order to investigate the response mechanism of alfalfa with different drought resistance to Drought-hardening process,this experiment was carried out before water stress to five alfalfa varieties with different drought resistance to drought-rehydration exercise process,and each variety was divided into CK group（normal culture）,D group（normal culture after water stress）and DH group（water stress after Drought-hardening）to analyze the effect of Drought-hardening on alfalfa yield and drought resistance by measuring the related indexes.The effect of Drought-hardening on the drought resistance of alfalfa was analyzed by measuring the indicators related to yield and drought resistance,and the photosynthetic parameters of the plants were also measured to investigate the effect of Drought-hardening on the photosynthetic system of alfalfa.The effects of Drought-hardening on the nutritional quality of different varieties of alfalfa were analyzed by measuring the nutritional quality indexes.The main findings were as follows:（1）Under water stress,drought-treated’Gannon No.1’,’Tourist’,and’Golden Queen’varieties all increased their plant height growth rate（6.1%,2.2%,and 3.1%,respectively）compared with the non-drought-treated treatment.The biomass of’Gannon No.1’,’Tourist’and’Dryland’alfalfa varieties after Drought-hardening was significantly higher than that of the water-stressed group,indicating that Drought-hardening could significantly increase biomass of the three alfalfa species’Gannon No.1’,’Tourist’and’Dryland’（P<0.05）.（2）Indicators related to drought tolerance:SOD activity,POD activity and MDA content of alfalfa decreased after Drought-hardening.The O₂^-content of’Gannon No.1’and’Visitor’varieties after Drought-hardening was significantly lower than that of the water-stressed group（P<0.05）.The H₂O₂contents of the four varieties’Gannon No.1’,’Suntory’,’Golden Queen’and’Dryland’were significantly lower（P<0.05）than the water stress group after Drought-hardening.It indicates that Drought-hardening can reduce the peroxide content of some varieties of alfalfa to a certain extent and mitigate the damage caused by water stress.（3）Photosynthetic parameters:Net photosynthetic rate of alfalfa of two varieties’Tourist’and’Golden Queen’was significantly higher（P<0.05）than that of water stress treatment after Drought-hardening.The net photosynthetic rate of the remaining three alfalfa species did not increase significantly.（4）Nutritional quality indicators:water deprivation leads to a reduction in the nutritional quality of alfalfa,the Drought-hardening process can improve the nutritional quality of alfalfa,with specific indicators of change depending on the species.Four alfalfa species,’Visitor’,’Suntory’,’Golden Queen’and’Dryland’that underwent Drought-hardening Sugar dry base content increased significantly compared to the water stress group（P<0.05）.The crude fat content of the three alfalfa species’Gannon No.1’,’Suntory’and’Dryland’was significantly higher than that of the water-stressed group after Drought-hardening（P<0.05）,indicating that three species alfalfa can increase sugar content and fat content through the process of Drought-hardening to improve the nutritional quality of the plants.The crude protein of four alfalfa species,’Gannon No.1’,’Visitor’,’Golden Queen’and’Dryland’,was Crude Protein accumulation in alfalfa significantly decreased after Drought-hardening（P<0.05）,indicating that the Drought-hardening process could not promote the accumulation of crude protein in these four varieties of alfalfa.In contrast,the accumulation of crude protein of alfalfa of’Suntory’variety increased significantly after Drought-hardening compared with the water-stressed group（P<0.05）,indicating that the Drought-hardening process of’Suntory’would increase the crude protein content of accumulation.The relative forage value of’Suntory’and’Golden Queen’alfalfa was significantly higher than that of the water stress treatment after Drought-hardening（P<0.05）,While the three alfalfa species’Gannon No.1’,’Visitor’and’Dryland’maintained high relative forage value under water stress treatment even if they did not experience the Drought-hardening process.Comprehensive analysis of the indicators showed that the yield and quality of alfalfa would be improved in different degrees after Drought-hardening.The’Gannon No.1’variety had more obvious yield and quality changes after Drought-hardening,while the rest of the varieties had different degrees of improvement in different indexes,which varied from variety to variety.Therefore,in the actual production process,proper Drought-hardening of alfalfa can increase its yield and improve its quality,thus achieving stable and high yield.