The identification and expression pattern analysis of CmPIPs gene family in melon could provide theoretical basis and support for further exploring the function of CmPIPs gene family and the genetic improvement of melon.TBtools,MEME,MEGA X and Plant-CARE tools were used to analyze the bioinformatics of CmPIPs,and the expression level of CmPIP2;7 in the pericarp of melon at different stages after pollination,and the expression level of each member of CmPIPs in different tissues and different concentrations of plant hormone treated young leaves were visualized in the software GraphPad Prism 10.The results showed that CmPIP2;7 and CsPIP2;8 had nearest kinship;the 12 members of the CmPIPs family were mainly distributed on chromosomes 1,3,4,5,9,10 and 11;except that CmPIP2;8 had 3 CDS regions,the other members had 4 CDS regions.The promoter regions of each member of CmPIPs had multiple cis-acting elements,hormone responsive elements,such as auxin,gibberellin,and abscisic acid.The expression level of CmPIP2;7 was significantly up-regulated during rapid development and maturity of melon fruit.Members of various families of CmPIPs were expressed in different tissues of melon.After treatment with 40.0 μmol/L auxin,the expression level of CmPIP2;4 was significantly up-regulated,while the expression level of CmPIP1;1,CmPIP 2;1,CmPIP2;2 and CmPIP2;3 were extremely significantly down-regulated,and when the concentrations of abscisic acid were 0.4,4.0 and 40.0 μmol/L,the expression level of CmPIP1;1,CmPIP2;1,CmPIP2;3,CmPIP2;9 were significantly down-regulated.After treatment with 44.640 μmol/L methyl jasmonate,the expression level of CmPIP2;1 and CmPIP2;5 were significantly down-regulated,while the expression level of CmPIP2;2,CmPIP2;3,CmPIP2;7 and CmPIP2;9 were significantly up-regulated.When the concentration of ethylene glycol was 4.0 mmol/L,the expression level of each member of CmPIPs was significantly up-regulated.The gene structure,sequence characteristics,evolutionary relationship and collinearity of CmPIPs gene family members were clarified,and their expression pattern were analyzed.

In order to improve the selection efficiency of melon materials with different pulp firmness types and accelerate developing varieties.The F₂ and BC₁F₁ populations were constructed with crisp melon materials 19A21,19A75 and soft melon materials N84,20S66 as parents.According to sensory testing statistics,the theoretical values of 3∶1 and 1∶1 for crispy and soft materials were consistent,indicating that the melon pulp firmness was controlled by a single gene,and crisp was dominant to soft.The changes of ACO activity and expression pattern of CmACO1 with different firmness types were analyzed with 4 materials.The results showed that the ACO activity of soft melon appeared at a peak during fruit development,but the crispy melon did not appear.The expression of CmACO1 in soft melon was significantly higher than that in crispy melon.This gene may be involved in regulating pulp firmness.According to the difference of insertion and deletion sites of CmACO1 in different materials,the InDel-Pf marker was developed.The InDel marker was used to detect the genotypes of 32 melon materials.Among them,crisp melon showed deletion band type,soft melon showed non-deletion band type,the marker polymorphism and pulp firmness were co-separated.Two F₂ populations were used to validate the InDel-Pf,the genotype and phenotype coincidence rates were 95.3% and 98.1%.The results showed that InDel-Pf marker had high accuracy in the actual identification of melon pulp firmness,which could effectively improve the efficiency of breeding selection and shorten the breeding cycle of improved varieties.

To further analyze the biological characteristics and expression of TrPLD family genes in Trichothecium roseum,four TrPLD genes were obtained by the whole-genome sequencing of Trichothecium roseum,the online tools of SMART,MEGA 7,ProtScale,SOPMA and other software were used to conduct bioinformatics analysis of TrPLD genes and their encoded proteins;RT-qPCR technology was employed to analyze TrPLD genes expression during the pathogen infection muskmelon fruit.Phylogenetic tree analysis showed that TrPLD1 had the closest genetic relationship with Colletotrichum aenigma with a homology of 63.89%;TrPLD2 had 74.57% homology with Purpureocillium lilacinum;TrPLD3 and TrPLD4 had the closest genetic relationships with Fusarium graminearu and Paecilomyces lilacinus,with homology of 65.38% and 55.45%,respectively.Bioinformatics analysis showed that the proteins of TrPLD1,TrPLD2,TrPLD3 and TrPLD4 all had two conserved domain HKD motifs.TrPLD3 contained PX and PH domains,besides the HKD structure.The four proteins belonged to unstable hydrophilic proteins,without signal peptide and transmembrane structure,and belonged to non-secretory proteins.The four proteins contained different numbers of phosphorylation sites,among which,TrPLD3 contained the most phosphorylation sites.Subcellular localization prediction showed that TrPLD1 and TrPLD3 were mainly located in the nucleus,and TrPLD2 and TrPLD4 were mainly located in the plasma membrane.RT-qPCR analysis showed that,during of simulation the pathogen infecting muskmelon fruit,taking the control expression as a control,the gene expressions of TrPLD1,TrPLD2,TrPLD3 and TrPLD4 increased significantly with the infection process,and the expression of TrPLD3 gene was significantly higher than other genes during the whole infection process.In summary,the four TrPLDs have different structures and biological functions,among which TrPLD3 plays an important regulatory role during the process of T.roseum infecting muskmelon fruit.

In order to investigate the resistant genes location of gummy stem blight(GSB) on chromosomes of melon, the resistance parent P181, susceptible parent P01 and F₂ progeny were used for GSB resistance genes identification. According to the disease incidence of GSB of F₂,two parents, 30 high-resistance and 30 high-suspect F₂ generations were choice to isolated DNA, in order to construct resistant and susceptible pools. The QTL locations were applicated by SLAF-seq and BSA technique. A total of 188 022 SLAF-labels were obtained, after low-quality SNP sites filterted out, 5 676 high-quality SNP markers were developed. Two GSB-resistance QTLs were identified on chromosomes of melon by the methods of SNP-index, which were located in Chr01 and Chr04, with 1.19 Mb (on the region of 9 837 447-11 028 838 bp) and 0.86 Mb (on the region of 33 135 224-33 993 540 bp) interval, respectively. A total of 218 genes were analysis in QTLs. Furthermore, according to the gene function annotations, 15 candidate genes were speculated with the relationship of GSB resistance, including 1 gene of NBS-LRR, 5 genes of E3 ubiquitin-protein ligase, 1 gene of RPM1-interacting protein, 1 gene of zinc finger protein, 1 gene of NAC domain-containing protein, 2 genes of calcium-dependent protein kinase, 3 genes of L-type lectin-domain containing receptor kinase, 1 gene of RING-H2 finger protein. The results will support reference of the basis of resistance genes of GSB.

The chlorophyll content of leave and the malonaldehyde(MDA)content of root were the important physiological index for identification of low temperature and low light in melon. In order to select the extreme material by the correct physiological data processing,eight core parental inbred lines were used to be evaluated. The evaluation results derived from two physiological index and the injury index were compared first. The injury index was calculated according to the injury classification. Two data processing methods were used in physiological data. One was using the measure value of SPAD and MDA after stress directly,another was using the absolute value of SPAD and MDA calculated between before and after stress. The compare results showed that under low temperature and low light stress,the leaf chlorosis and macerating root was happened in melon seedling. The SPAD value of poor tolerance melon inbred lines was getting smaller and the MDA content was getting larger. Using the measure value of SPAD and MDA after stress directly could get the same low temperature and low light stress tolerance results with which identified from injury index. The absolute value of SPAD and MDA calculated between before and after stress could used to evaluate accessorily the sensitive ability to stress for inbred lines. The tolerance inbred line of P143 and the sensitive line of P149 were selected for further research of molecular selection. The results were useful to uniform the low temperature and low light identification in melon and to provide reference for other stress data processing.

In order to study the effects of different concentrations of cadmium stress on the growth and physiological characteristics of different thin-skinned melon varieties at seedling stage,hydroponic methods were conducted with based on previous experiments,and the thin-skinned melon varieties XTG(relatively high accumulation species)and IVF-28(relatively low accumulation species)were selected as trial cultivars. Four different CdCl₂ concentrations of 0,30,60,and 100 mg/L were set,the changes of shoot growth,root growth and physiological and biochemical indexes under different Cd stress concentrations were studied. The results showed that the plant height,stem thickness,total root length,root surface area,root volume,root tip number,and fractal dimension of XTG and IVF-28 all decreased as the concentration of Cd stress increased. And the decrease of XTG was lower than that of IVF-28. With the increase of Cd stress treatment concentration,the physiology of the two tested thin-skinned melon varieties also changed. The SOD,MDA and H₂O₂ contents increased with the increase of Cd stress treatment concentration,and the POD activity and GSH content reached the maximum under 60 mg/L CdCl₂ treatment,while CAT activity and PRO content reached the maximum when 30 mg/L CdCl₂ treatment,in which the physiological and biochemical indicators of XTG were higher than IVF-28. The results showed that X-T-G,a thin-skinned melon variety,had a lower decline in growth-related indicators than IVF-28 under Cd stress,and physiological indicators were higher than IVF-28,indicating that X-T-G had high tolerance to Cd stress than IVF-28.

Two leaves and one new period was the sensitive period of melon to low temperature and low light condition, which period was always used to chlorophyll content determination and tolerance material selection. There were three leaves in this period, but no research mentioned about the definite measure leaf. To understand these and select the suitable measure leaf for chlorophyll content prediction by SPAD value determination, the chlorophyll content and SPAD value of three leaves of two leaves and one new period melon were collected and analyzed. The three leaves from bottom to up (Y1, Y2 and Y3) at different position of melon inbred line of P148 was selected to determinate and analyze the variation and correlation of SPAD value and chlorophyll content in two leaves and one new period by One-Way-ANOVA, Correlation and Regression program of SPSS 13.0 soft, respectively. The SPAD value and chlorophyll content were increased with increasing of leaves position. The Y3 showed the higher SPAD value and chlorophyll content than Y1 and Y2 significantly. The correlation between SPAD value and chlorophyll content was reduced with increasing of leaves position.The SPAD value and chlorophyll (a+b) content of Y1 had highest R value, the regression equation was established: y(Chla+b)=0.032x(SPAD)-0.141，R²=0.699. The first leaf was selected to determinate the SPAD value for chlorophyll content prediction to mass screen the low-temperature-and-light tolerance melon.

In this experiment, Qingya Baiyu, a thin-skinned melon cultivar, was used as the research object. Four different concentrations of CO₂ were applied to thin-skinned melon from seedling stage. Afterwards, the effects of vine elongation on photosynthesis and growth of plants were studied to reveal the primary mechanism of photosynthesis improvement and determine the optimum CO₂ concentration for thin-skinned melon cultivation in greenhouse in winter and spring in Northern China, providing theoretical basis for precise fertilization of thin-skinned Melon Cultivation in winter and spring facilities. Four kinds of CO₂ concentrations:(400±12) μmol/mol(CK), (800±24) μmol/mol(T1), (1 200±36) μmol/mol(T2), (1 600±48) μmol/mol (T3), were applied to melon plants, respectively. Dry and fresh weight, chlorophyll content, photosynthetic parameters, light response curve, CO₂ response curve and chlorophyll fluorescence parameters of melon plants at elongation stage were determined. The results showed that compared with CK, T3 treatment increased plant fresh weight 116.03%, aboveground fresh weight 118.66%, dry weight 78.70%;reduced dry-fresh ratio 17.28%, root shoot ratio 50.12%;increased net photosynthetic rate 221.55%, stomatal conductance 208.85%, intercellular carbon dioxide concentration 429.74%, transpiration rate 394.49%, maximum net photosynthetic rate 71.52%, the light saturation point 64.07%, apparent quantum efficiency 16.9%; reduced light compensation point 40.0%; increased maximum regeneration rate of RuBP 78.43%, actual quantum yield of PSⅡ 44.3%, photochemical quenching qP, qL 32.79%, 43.14%, photosynthetic rate ETR 41.1%. Compared with CK, T1 treatment increased chlorophyll a content 6.28%, maximum catalytic rate of Rubisco enzyme 52.8%, The VTPU 35.13%; reduced Fo 11.69%, Fo' 14.09%, Fm 16.01%, Fm' 18.92%, Ft 22.03%. So CO₂ fertilization could effectively improve plant growth, improve photosynthesis, electron transfer efficiency, increase light saturation point, increase CO₂ saturation point, reduce light compensation point, increase plant biomass, T3 ((1 600±48) μmol/mol) treatment effect significantly. The reason for increasing photosynthesis was due to the increasing chlorophyll content and the transport rate of propionate phosphate in low concentration, while the high concentration was mainly due to the increasing actual quantum yield Y(Ⅱ) of PSⅡ, photosynthetic electron transfer rate and photochemistry quenching.

Brassinosteriod is a necessary for plant to regulate the plant physical activities, and DWF1 is one of most critical enzymes involved in brassinosteriod biosynthesis. In order to study the function of DWF1 in melon fruit development, the gene CmDWF1 was cloned from melon for analyzing the nucleotide and amino acid sequences. RT-PCR method was used to analyze the gene expression characteristics. The results showed that the open read frame length of CmDWF1 was 1 701 bp, encoding 566 amino acids. The predicted protein molecular weight of CmDWF1 was 66.115 11 ku, the theoretical isoelectric point was 6.96, the instability index was 48.18 and the GRAVY was -0.402. Signal sequence was not found and the location coefficient in the cytoplasm was 9, which suggested that the protein was localized in cytoplasm. The secondary structure of CmDWF1 protein contained 37.81% of alpha helix, which was relatively high. The CmDWF1 protein contained a FAD-binding-4 domain, which suggested that the protein acted as a FAD oxidoreductase. Phylogenetic analysis showed that Cucumis melo had closer relationship with Cucumis sativus. Real-time fluorescent quantitative analysis indicated that CmDWF1 could express in roots, stems and leaves, but the highest expression level was in roots. And the expression level increased significantly in the 25 d fruit after pollination, but decreased in 35-45 d fruit. These results demonstrated that CmDWF1 might be associated with the biosynthesis of brassinosteriods and then regulated the growth and development of melon.

To obtain the genes related to fruit maturation of melon, the genome-wide identification of four gene families, HB(Homeobox),RIN(Ripening inhibitor),ETR(Ethylene receptor) and CTR(Constitutive triple reaction) from melon, which were related to ethylene biosynthesis and signal transduction, were carried out in the study. A total of 17 members of CmHB family,21 members of CmRIN family,3 members of CmETR family and 20 members of CmCTRs family were retrieved from the melon genome, which were further verified by sequence alignment and motif analysis. Using transcriptional profiling analysis, the expressions of the four gene family members in wild type Cucumis melo L.cv Hetao and transgenic Cucumis melo L.cv Hetao with antisense CmACO1 gene (M9) were determined during growth period and at ripening stage of fruits. The results showed that 13 genes were differentially expressed between the two developmental stages of fruit in wild type melon, of which the expression amount of CmHB3 and CmHB11 in growth period was, respectively, 42 and 9 times that at ripening stage, but the expression level of CmHB4 at ripening stage was 27 times that in growth period, all reaching to a highly significant level. And 12 genes were also differentially expressed between two developmental stages of fruit in M9 transgenic line, among which the expression amount of CmHB3 and CmHB11 in growth period was, respectively, 6 and 3 times that at ripening stage, while the expression level of CmHB4 at ripening stage was 41 times that in growth period, all the differences being highly significant. During the growth of fruit, the expression levels of CmHB3 and CmHB11 had extremely significant difference, and the expression levels of CmRIN14 and CmRIN15 were significantly different between wild type and M9 fruits. At ripening stage of fruit, the difference in expression level of CmHB3 was highly significant and the differences in expression levels of CmRIN14 and CmRIN15 were significant between two types of melon fruits. In addition, the expression patterns of CmRIN14 and CmRIN15 between the two melon materials presented a opposite trend,indicating that their expression patterns were affected by the expression level of CmACO1.

In order to study the inheritance of melon T115,founding the molecular markers linked to resistance genes and locating the resistance genes.Parental lines and(T115 SP Hongxincui) F₁,F₂,back cross populations BCr and BCs were scored for response to inoculation with[Pseudoperonospora cubensis (Berk.etCurt.) Rostov.].The simple sequence repeat(SSR) technique and bulk segregant analysis(BSA) were used to identify molecular markers linked to the resistance of melon downy mildew.A total 1 090 pairs SSR primers could detect the polymorphism between the resistant pool and susceptible pool which based on the ICuGI constructed genetic linkage map.The resistance to downy mildew in T115 was controlled by one single dominant gene. An unique 120 bp fragment was amplified with the primer DM0073.It was identified that was linked to resistance gene of T115 at a distance of 3.6 cM.The resistance gene was located to LG1.This SSR bands indicated that the marker could be useful for marker assisted selection in melon breeding for downy mildew resistance.

In order to study the inheritance of wild melon PI414723,founding the molecular markers linked to resistance genes and locating the resistance genes.The F₂,BCr and BCs populations were derived by crossing and back crossing with Cucumis melo ssp. melo lines PI414723 and kalakesai.Investigation and statistical analyses scored for response to inoculation with[Pseudoperonospora cubensis (Berk.etCurt.) Rostov.].Based on the genetic linkage map that was constructed by the ICuGI.SSR analysis,combined with bulked segregation analysis(BSA),was done on the DNA of F₂ using 1 090 pairs of SSR primers.The results indicated that the resistance to downy mildew in PI414723 was controlled by one single recessive gene. An unique 226 bp fragment was amplified with the primer DM0231.It was identified that was linked to resistance gene of PI414723 at a distance of 2.67 cM.The resistance gene was located to LG9.This SSR marker DM0231could be useful for marker assisted selection in melon breeding for downy mildew resistance.