Effects Of Salt Stress On Sorghum Growth And Rhizosphere Bacterial Diversity

Salt stress has an adverse effect on plant growth.It is one of the main limiting factors to crop yield.Improper land use leads to the continuous expansion of saline-alkali land.Planting salt-tolerant crops and breeding salt-tolerant varieties will promote the use and improvement of saline land.Plants have internal regulatory mechanisms to cope with fluctuations in environmental conditions and external stress.At the same time,plant roots can adapt to poor growth environments through complex interactions with soil microorganisms.Sorghum is one of the most important food crop and energy plants in the world.It has strong stress resistance and high biological yield.In this research,different salt-tolerant sorghum varieties were subjected to salt stress.By testing the changes of physiological and biochemical indexes of sorghum under salt stress conditions,the effects of different salt stress levels on the growth of sorghum were studied.High-throughput sequencing technology was used to analyze the bacterial community structure changes of rhizosphere bacterial of different sorghum varieties at different development stages under salt stress.The results will provide a theoretical basis for the selection of sorghum salt-tolerant resources and the utilization of germplasm resources.The main results are as follows:1.Under salt stress,the sorghum morphology changed significantly,and the plant height,node length,and stem thickness reached the maximum at S0 or S3 treatment.However,with the increase of stress concentration,the inhibitory effect of stress on sorghum growth gradually increased.The changes of antioxidant enzyme activities of the two varieties under the four salt stress levels were the similar,both increased with the extension of stress time,while the MDA activity increaseed continuously with the extension of stress level and stress days.The strong resistance of GLZ to salt stress correlated with its strong antioxidant enzyme activity.Flavonoid and phenol,as important non-enzymatic antioxidants,changed significantly under the induction of salt stress.The total phenol and flavone content increased after salt stress treatment,and reached the highest level under S3 treatment.And the contents of phenol and flavonoid in the soil also showed significant differences.2.After salt stress,the photosynthetic rate of the two varieties decreased,the intercellular CO2 concentration(Ci)increased.The photosynthetic capacity of sorghum was stronger under S3 stress,and decreased significantly under S5 and S7 stress.The change of chlorophyll content increased first and then decreased with the increase of salt stress.With the prolongation of the growth period,salt stress decreased the chlorophyll content of sorghum leaves.The grain fat and starch contents of the two sorghum grains continued to decrease under salt stress,and the grain protein content was the highest in S3.The grain tannin,total phenol and flavonoid content of the two varieties increased with the increase of salt stress.3.16S rDNA high-throughput sequencing analysis of microbial community composition and diversity showed that Proteobacteria,Actinobacteria,Acidobacteria,Chloroflexi,Bacteroidetes and Firmicutes are the predominant microbial groups in soil microorganisms.4.Among sorghum varieties,growth periods and soil salt concentration,salt concentration has the greatest impact on microorganisms.Under low salt concentration,the diversity of root soil microorganisms is higher,while under high salt concentration,the diversity decreases.There were a significant correlations between environmental factors and species.Salt concentration,MDA and photosynthetic parameter(Ci,Pn,Gs)were the main environmental factors that significantly affected the bacterial community structure of sorghum rhizosphere soil in four salt concentrations.This result has enriched the understanding of sorghum rhizosphere soil microbial diversity.