Effects Of Salt-alkali Stress On Seedling Growth And Rhizosphere Soil Microbial Diversity Of Cabernet Sauvignon

The eastern foot of Helan Mountain in Ningxia is one of the characteristic industries in the autonomous region,with a wide area of grape cultivation,and its soil salinization restricts the development of grape industry.Therefore,in this study,one-year-old Cabernet Sauvignon seedlings were used as the research object,and three saline-alkali groups were set up to simulate the saline-alkali composition in the eastern foot of Helan Mountain in Ningxia,with four different concentration gradients of 0,50,100 and 150 mmol·L-1 in each group.The growth,physiological and photosynthetic indexes were measured,the soil physical and chemical properties and soil enzyme activities were determined based on the rhizosphere soil of the seedlings,the bacterial diversity and bacterial community characteristics of the rhizosphere soil were determined by high-throughput sequencing,and the correlation between soil bacterial community characteristics and physical and chemical properties was analyzed.The results are as follows:The results are as follows:1)Saline-alkali stress has an inhibitory effect on the growth of Cabernet Sauvignon seedlings,low concentration of saline-alkali is suitable for the growth of Cabernet Sauvignon,while high concentration is not conducive to its growth.The MDA content in leaves of Cabernet Sauvignon seedlings increased first and then decreased with the increase of salt concentration.The intercellular CO2 concentration(Ci),net photosynthetic rate(A)and transpiration rate(E)of Cabernet Sauvignon seedlings decreased with the increase of concentration,and the photosynthesis of leaves decreased under saline-alkali stress.2)Through the analysis of chemical properties of grape rhizosphere soil under different salt-alkali stress treatments,the higher the concentration,the higher the content of total nitrogen and available phosphorus in rhizosphere soil,the greater the pH and conductivity values,and there was no significant difference in organic matter and total phosphorus content in each treatment group.Under mixed salt-alkali stress,the activity of soil catalase increased first and then decreased with the increase of salt concentration.The activities of soil urease,phosphatase and sucrase decreased with the increase of soil concentration.The soil nutrient content and enzyme activity were higher when the salinity and alkalinity were lower,but the enzyme activity was inhibited when the salinity and alkalinity were higher,and the physical and chemical environment of rhizosphere was poor,which was not conducive to the growth of Cabernet Sauvignon seedlings.3)Through the analysis of the bacterial community structure of grape rhizosphere soil under different 2saline-alkali stress treatments,the number of bacteria in the soil decreased,and the richness of bacterial community in the rhizosphere soil of Cabernet Sauvignon seedlings also decreased with the increase of saline-alkali stress concentrations.Under mixed stress,the number and species of bacteria in the rhizospheric soil of Cabernet Sauvignon seedlings were higher in treatment A and B,and lower in treatment C.At the genus level,the relative abundance of 10 dominant genera changed,the first dominant genus was Hirschia,and the total proportion of different treatments was 23.84%,and the most dominant phylum was Proteobacteria.The total number of OTUs in the soil of saline-alkali treatment groups A,B and C were 7802,8245 and 8287,respectively,and the number of common bacteria OTUs in the soil of treatment A was the largest,while the number of OTUs in treatment C decreased with the increase of concentration.4)By studying the correlation between environmental factors and bacterial community structure under different treatments,it was found that pH was negatively correlated with ACE index,chaol index and Observed_species,pH was an important limiting factor for the number and species of bacteria,and organic matter was positively correlated with PD_whole tree.There was a significant correlation between total nitrogen content and ACE index.There was a significant positive correlation between available potassium and Firmicutes,a significant positive correlation between pH and Proteobacteria,Bacteroidota,and a significant negative correlation between conductivity and Chloroflexi;Total N and available P were positively correlated with Chloroflexi,while available N and total P were positively correlated with Grenarchaeota,and total P was negatively correlated with Actinobacteriota.