Salt-tolerant Germplasm Screening Of Rice And The Effect Of Potassium On Salt-stress Mitigation

With the expansion of the area of saline alkali land,the shortage of food supply caused by the increase of population will be further intensified,and the maximum use of saline alkali land has become an urgent problem in agricultural science.Rice is the second major food crop in the world.Breeding salt tolerant varieties that can grow normally on the saline alkali land is an effective measure for the restoration and utilization of the saline alkali land and a new way to solve the problem of food security.In this study,28 kinds of rice were selected as the research object.Three different concentrations(0 mM,100 mM,200 mM)of salt stress were applied to rice seedling stage by hydroponics.The changes of plant height,fresh weight,dry weight,chlorophyll content,photosynthetic rate and other growth and physiological indexes were detected,and salt tolerant,medium salt tolerant and sensitive rice varieties were screened.In order to study the effect of potassium on the salt tolerance of rice,three salt tolerant and three sensitive rice varieties were selected according to the above screening results.Under the salt concentration of 0 mM,100 mM,KCl(10 μM,100 μM,2 mM,10 mM)were treated with different concentrations.The related growth and physiological indexes of six rice varieties were measured to explore the alleviating effect of potassium on salt stress injury.The main results of this study are as follows:1)The effect of salt stress on the growth of 28 kinds of rice and the selection of salt toleranceWe evaluated the salt tolerance of 28 rice varieties by 100 mM and 200 mM salt concentration in three leaf stage.After salt stress,the growth and development of rice seedlings were obviously inhibited,such as the plant became shorter,biomass decreased,leaves withered and even died,photosynthetic rate decreased,chlorophyll content decreased,and the higher salt concentration,the more obvious the above symptoms.Under the same salt concentration stress,the physiological and biochemical responses of different rice varieties to salt stress are different.Under the low salt concentration environment,the salt stress symptoms of rice plants are not obvious,and the photosynthetic characteristics and chlorophyll content have no significant difference compared with the control.According to the difference of salt sensitivity,28 rice varieties were divided into three categories: Salt resistant varieties:POKKALI、C858、JC118S、SE337、C622、SE293、SE146、C613、C38.Middle salt tolerant varieties: R1、G127、G201、IR29、SE217、C991、G504、SE205、SE95、SE148.Sensitive varieties: C616、C152、C146、C1005、SE75、SE45、SE210、C310、C57.2)The alleviating effect of potassium on different rice varieties under Salt StressThree salt tolerant rice varieties(C858、G201、POKKALI)and three sensitive rice varieties(SE45、SE75、SE210)were selected to test the effect of K on salt stress.After K application,the biomass,photosynthetic rate and chlorophyll content of six rice varieties increased significantly,photosynthetic rate increased and necrotic leaves decreased,which alleviated the damage of salt stress.The results showed that the biomass growth of C858,G201 and POKKALI was significantly higher than that of SE45、SE75 and SE210.The release effect of K on rice is also related to the concentration of KCl.The experimental results show that the more KCl is applied,the better.It should be determined according to the degree of salt stress on rice.In this experiment,the concentration of NaCl was 100 mM,and the best KCl content in rice growing environment was 2 mM.In addition,under the condition of control cultivation,KCl alone increased the plant height,fresh weight and chlorophyll content,which indicated that potassium element promoted the growth of plants.