Physiological Response Of Seed Watermelon To Drought Stress And Gene Expression Profile Analysis

Four varietiesof seedwatermelon were selected from 12 seed watermelonthroughscreening experiments.Two drought stresses were simulated by potted water control,PEG drought simulation.The aim was to observe the effects of drought stress on external morphological characteristics,determine internal physiological and biochemical indexes,and evaluate seed germination,explore the drought resistance and adaptability of different varieties.The results were achieved as follows:1.The drought damage index of 12 seed watermelon varieties was calculated on the basis of the criteria of drought damage classification.In line with the drought damage index,four seed watermenlon with inconsistent drought resistance were selected for further drought resistance evaluation.They are Linzi No.1(H17),Heifeng No.1(H28),Keaohong(R12)and Hongxiu No.3(R06).The drought stress treatment(0d,2d,4d,6d,8d)by potted water control showed different degrees of wilting with the prolongation of drought stress.Drought stress generally made plant’s height and root’s length reduced,dry matter quality accumulation decreased,and root-shoot ratio increased.2.Study the morphological and physiological of them under different drought stress by potted water control.In the test of artificial drought stress,with the increase of drought stress,malondialdehyde(MDA)、POD activity and proline content increased gradually;and thenSOD activity increased first and then decreased,POD activityalways represented an upward trend.The content of soluble protein always represented an upward trend with the prolongation of drought stress,the most of conspicuous was Linzi No.1(H17).According to the membership function method,the order of drought resistance of the four varieties was determined as Linzi No.1(H17)>Heifeng No.1(H28)>Keaohong(R12)>Hongxiu No.3(R06).3.PEG-6000 solution(0,-0.10,-0.20,-0.40,-0.80MPa)was used to simulate drought stress to compare the seed germination and growth of the four varieties.The drought tolerance was evaluated comprehensively by membership function method.The results showed that with the increasing concentration of PEG,the number of seed germination decreased.When osmotic potential reached the maximum stress concentration of-0.80 MPa,all the numbers of the germinated seeds of the cultivarswere not over 5.According to the membership function method,the order of seed germination strength of the four kinds of watermelon seeds for seed use was Linzi No.1(H17)>Heifeng No.1(H28)>Keaohong(R12)>Hongxiu No.3(R06).The obtained drought-resistant array order was consistent with the drought-resistance results in the artificial water control environment.4.Four seed watermelon varieties were growed in two ecological environments,the yield and quality of fruit were analyzed.To verify the drought resistance of different seeded watermenlons conjunction with the previous physiological conclusion.The results showsthat drought resistance of H17 was best,drought resistance of R06 was worse,but its quality of fruit was best.5.The seed watermelon H17 and watermelon jingmei8 K were used as material to compare and find the differences of quality,physiology in storage.The peel thickness、peel firmness、soluble solid content、vitamin C、soluble pectin content、 PG activity、SOD activity and PODactivity.The results shows that thestorability fruit of seed watermelon H17 flavor is better than watermelon jingmei8 k.6.“Linziyihao”,a cultivar of seed watermelon,was used as experiment material,and was conducted drought stress.Complementary DNA library was prepared based on isolated total RNA of leaves,and high-throughput sequencing was done by HiSeq X-ten system.Differentially expressed genes of seed watermelon under drought stress treatment were analyzed.Function and pathway of those different expression genes were also investigated using Gene Ontology(GO),COG,and KEGG pathway databases.The results showed that the 42.09 Gb transcriptome data were obtained,and the base ratios with quality values higher than 30 in reads(Q30)were more than 93%.The sequence alignment was performed between clean reads and watermelon genome,and 95.37%-96.36% reads could be compared to watermelon genome.Based on GO function annotation classifications of differentially expressed genes,132 genes annotations were obtained.The function of these genes includes cell part,organelle,membrane,cell process,single-organism process,metabolic process,binding,catalytic activity,nucleic acid binding transcription factor activity,etc.Differentially expressed genes of COG function annotation classifications includes general function prediction only,transcription,signal transduction mechanisms,replication,recombination and repair,carbohydrate transport and metabolism,secondary metabolites biosynthesis,transport and catabolism,etc.KEGG enrichment analysis indicates that differentially expressed genes includes aminoacid,terpenoi,carbohydrate,steroid,sphingolipid,ascorbate and alkaloid metabolism,and plant hormone signal transduction.