Screening Of Waterlogging-tolerant Germplasm Resources And Preliminary Study On Waterlogging-tolerant Mechanism Of Pumpkin

Pumpkin is an important economic crop with high nutritional value and health care function.In Huang-huai area of China,pumpkin fruit growth peak in July and August,and this period is in the rainy season,pumpkin production often suffers from waterlogging.Therefore,it is of great significance for pumpkin production to carry out the screening of waterlogging tolerance germplasm resources and the study of waterlogging tolerance mechanism.In this study,27 Chinese pumpkin resources were used as the research object to screen the pumpkin waterlogging tolerance resources.According to the screening results,the waterlogging tolerance mechanism of pumpkin was studied at the physiological and biochemical and transcriptome levels.The main results are as follows:1.After waterlogging stress,the biomass,chlorophyll content,malondialdehyde content,SOD enzyme activity and proline content of 27 pumpkin materials changed to varying degrees.Among them,the biomass and chlorophyll content of all materials decreased,SOD enzyme activity and proline content increased in some materials and decreased in some materials,and the malondialdehyde content of most materials increased.Principal component analysis,membership function analysis and cluster analysis were carried out on 16 evaluation indexes of 27 pumpkin materials.Finally,27 pumpkin materials were divided into three categories.Among them,’ 013-2 ’ and ’ Chang yi ’ are waterlogging-tolerant materials,’ 063-2 ’and ’ 367-2 ’ are waterlogging-sensitive materials,and the rest are medium waterlogging-tolerant materials.2.With the extension of flooding time,the SOD,POD,CAT and APX activities of waterloggingtolerant materials(’ 013-2 ’,’ Chang yi ’)and waterlogging-sensitive materials(’ 063-2 ’,’ 367-2 ’)showed an overall upward trend,and the waterlogging-tolerant materials were higher than the waterloggingsensitive materials.The activities of ADH,LDH,PDC and PDH in waterlogging-tolerant materials showed an overall upward trend,and the activities of ADH,LDH,PDC and PDH in waterlogging-sensitive materials showed a trend of first increasing and then decreasing.The lactic acid and ethanol contents of waterlogging-tolerant materials and waterlogging-sensitive materials showed a trend of increasing first and then decreasing.The content of pyruvate and proline in waterlogging-resistant materials and waterloggingsensitive materials showed an overall upward trend.The malondialdehyde content of waterlogging-resistant materials and waterlogging-sensitive materials showed an upward trend,and the waterlogging-resistant materials were lower than the waterlogging-sensitive materials as a whole.After waterlogging stress,the relative expression levels of SOD,POD,CAT and APX genes in the leaves of waterlogging-tolerant pumpkin materials(’ 013-2 ’)were up-regulated during the waterlogging time,and were higher than those of waterlogging-sensitive materials(’ 367-2 ’).3.The results of transcriptome sequencing showed that 3231 differentially expressed genes were screened from the leaves of waterlogging-tolerant pumpkin ’ 013-2 ’ and waterlogging-sensitive pumpkin ’367-2 ’,including 1778 up-regulated genes and 1453 down-regulated genes.Through GO enrichment analysis of differentially expressed genes,the results showed that differentially expressed genes were significantly enriched in biological processes such as photosynthesis,ethylene response,phosphate signal transduction system,cell response to ethylene stimulation,and ethylene activation signaling pathway.Through KEGG annotation of differentially expressed genes,947 differentially expressed genes were annotated into 121 metabolic pathways.Differentially expressed genes were significantly enriched in metabolic pathways such as photosynthesis-antenna protein,plant hormone signal transduction,MAPK signaling pathway-plant,plant-pathogen interaction,phenylpropanoid biosynthesis.Through KOG annotation classification,a total of 1564 differentially expressed genes were annotated into 24 functional classifications.Among them,the annotated differentially expressed genes were mainly annotated in general function prediction,signal transduction mechanism,(protein turnover,molecular chaperone),(carbohydrate transport and metabolism),(biosynthesis,transport and catabolism of secondary metabolites).The alternative splicing events of differential grouping were mainly focused on exon skipping(SE)and mutually exclusive exons(MXE).In addition,a total of 119036 synonymous mutations,88166 missense mutations,927 nonsense mutations and 155 stop codon mutations were found by SNP analysis.