| The deterioration of soil salinization has caused great harm to modern agricultural production in the world.Sorghum is not only one of five main crops,but also an outstanding salt tolerant crop.The screening and identification of sorghum salt tolerance will be very important to the development and utilization of salinized land,increasing grain yield and maintaining sustainable agricultural development.In this experiment,270 sorghum cultivars were selected to test salt tolerance at germination(200 mmol L-1NaCl treated)and seedling stages(100 mmol L-1NaCl treated).The two germination indicators including the germination potential and the germination rate,as well as seven seedling indicators,including the relative chlorophyll content?SPAD?,seedling length,root length,seedling fresh weight,seedling dry weight,root fresh weight,root dry weight were measured.The relative values of various indicators under salt stress were calculated,showing that the relative germination potential and relative germination rate of 270 sorghum cultivars were 0%–98.89%and18.06%–117.74%,and The seven seedling indicators were 59.54%-120.19%,52.48%-111.82%,46.73%-148.97%,27.43%-134.94%,30.48%-140.70%,21.62%-151.02%,31.46%-133.05%,respectively.Combined the membership function value analysis with cluster analysis,the salt tolerance ability of the 270 cultivars at germination stage and seedling stage was comprehensively evaluated and the 270 cultivars were clustered into four groups.A batch of sorghum landraces with salt tolerance at germination and seedling stages were identified,especially Dahongliang?00000450?from Hebei province showed high salt tolerance at both stages,which can be used as an excellent resource for subsequent salt tolerance identification and salt tolerance breeding at the whole growth period.There was no significant correlation in salt tolerance between the germination stage and the seedling stage.Full-length transcriptome sequencing of samples that the most salt-tolerant cultivar Gehong?00000601?and the most sensitive salt cultivar Hegaoliang?00013200?identified at the seedling stage were treated with 150 mmol L-1NaCl for 0,6,24,and48 hours.The main results are as follows:?1?Completed the transcriptome sequencing of 24 samples,and the number of full-length transcripts obtained from each sample ranged from 5,289,450 to 11,501,746.Redundant transcripts were removed after all consensus isoforms mapped to the reference genome,and 66751 transcripts were finally obtained..SSR prediction was performed on the de-redundant transcripts,and a total of 16914 SSRs were obtained.The de-redundant transcripts of all samples were compared with known annotations of the reference genome.Among them,there were 2475 novel gene loci and 41631 novel transcripts were found.The sequence structure of the newly discovered transcripts was analyzed,and a total of 20878 complete ORFs and 1318 lncRNAs were predicted,and the function of 38185 novel transcripts was annotated.Transcription factor prediction was performed for novel transcripts,and a total of 3185 transcription factors were predicted.?2?Salt-tolerant and salt-sensitive cultivars had 18443 and 18060 gene expressions,respectively,and 728 and 268 genes were specifically expressed in each sample after NaCl treatment.?3?Salt-tolerant cultivars Gehong treated with NaCl for 6,24,and 48h had 1596,2432,647 genes differentially expressed,1026,1517,307 genes were up-regulated,and570,915,340 genes were down-regulated;Salt-sensitive cultivars Hegaoliang had 758,316,and 472 genes differentially expressed,of which 453,165,and 347 genes are up-regulated,and 305,151,and 125 are down-regulated genes;the number of differentially-expressed genes in salt-tolerant cultivars is much more than that of sensitive genes.STEM analysis of the co-expression patterns of differentially expressed genes under salt stress indicated that the expression trends of significantly enriched differentially expressed genes in the two cultivars were completely different.?4?Combining GO enrichment and KEGG enrichment analysis showed that there were differences in the enrichment results at three time points of salt-tolerant cultivars,and much more same enrichment terms in salt-sensitive cultivars.The differentially expressed genes of the 2 cultivars were mainly involved in catalytic activity,membrane components,Related processes include protein translation,processing and hydrolysis,amino acid synthesis and metabolism,photosynthesis,and flavonoid biosynthesis.Analysis of differentially expressed genes enriched to salt stress response?GO term?after salt stress in 2 cultivars,81 genes were enriched into this term in salt-tolerant cultivars,while salt-sensitive cultivars only had 26 genes,of which 11 genes were differentially expressed in both cultivars.The expression of LOC8080517 gene in the two cultivars differed by a hundred times and the expression patterns in the 2 cultivars were completely different.?5?There were 5940 differentially expressed transcripts before and after salt stress in salt-tolerant cultivars,of which 190 were differentially expressed transcription factors;2339 differentially expressed transcripts and 58 differentially expressed transcription factors were identified in salt-sensitive cultivars. |
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