Effects Of Saline-alkali Stress On Growth And Development Of Silage Maize Seedlings And Transcriptome Analysis

Maize is one of the three major crops in the world,and it is also the crop with the most extensive planting area and the highest total output in China.However,maize is a salt-sensitive plant with relatively poor salt tolerance.Its limit salinity is 1.7/dsm(1dsm=0.01 mol/L),and the yield decreases by 12% for every 1/dsm exceeding the limit salinity.In this experiment,silage maize Da Jingjiu 26 and its female parent inbred line Chang7-2 were selected as test materials to investigate the effects of salt-alkali stress on seed germination,seedling morphological characteristics and physiological characteristics of silage maize,and improve the mechanism of salt-alkali tolerance of maize.High-throughput transcriptome sequencing technology was used to study the differentially expressed genes of maize in response to salt stress during germination,and to analyze the molecular regulation mechanism of maize in response to salt stress from the RNA level.The results of the study are as follows:1.Effects of salt-alkali stress on seed germination of maize:Under mixed saline-alkali stress,the germination potential,germination rate and vigor index of silage corn seeds all showed a decreasing trend.Under the same salt concentration,higher p H value caused more significant damage to seed germination.50 mmol/L salt treatment can promote the growth of maize radicle.Under higher concentration of saline-alkali stress,maize germ and radicle growth are severely inhibited.And,with the increase of salt concentration,the biomass of maize bud stage decreased.2.Effects of salt-alkali stress on morphological characteristics of maize seedlings:With the increase of salt-alkali concentration,the seedling height of maize decreased significantly,and the seedling height of each group under 200 mmol/L salt-alkali treatment decreased by more than 40% compared with the control.The leaf area of maize seedlings showed a decreasing trend under different concentrations of saline-alkali stress.With the increase of saline-alkali treatment concentration,both the dry and fresh weight of seedlings above ground and below ground showed a downward trend,and the decline of biomass in the ground was larger than that in the shoot.Under the saline-alkali treatment of 50 mmol/L,the root length of some maize seedlings was larger than that of the control,but with the increase of salt concentration,the root length of the seedlings decreased compared with the control.3.Effects of salt-alkali stress on physiological characteristics of maize seedlings:The leaf SPAD value of maize seedlings under each saline-alkali treatment was significantly lower than that of the control,and the SPAD value of leaves under the 200mmol/L treatment decreased by more than 30%.With the increase of salt concentration,the relative water content and MDA content of maize seedling leaves showed an overall downward trend.The relative electrical conductivity,soluble sugar content and soluble protein content of maize seedling leaves showed an upward trend under the treatment of higher saline-alkali concentration.The proline content of maize seedling leaves showed an overall upward trend under saline-alkali stress,and the growth was slow under the saline-alkali stress of 50 mmol/L.Under the saline-alkali stress,the proline content in the leaves of maize seedlings increased by 2-3 times compared with the control.The antioxidant enzyme activities of maize seedling leaves under saline-alkali stress generally increased first and then decreased with the increase of saline-alkali concentration.4.Transcriptome analysis of maize in response to salt stress at germination stage:Transcriptome sequencing and data analysis were performed on the germ of maize inbred line Chang 7-2 under salt stress.The results showed that a total of 40 290 Unigenes were annotated,including 615 DEGs.In the GO enrichment analysis of DEGs,the top 20 classes with obvious enrichment were analyzed.21 DEGs were enriched in phenylpropanoid biosynthesis pathway,which was the most significant KEGG enrichment pathway.The DEGs were classified into 25 COG groups.In addition,13 important transcriptional factor were selected for further analysis,including MYB,WRKY,AP2,b ZIP,b HLH and NAC families.