Study On Mechanisms Of Seed Germination And Seedling Growth Of Cucumber By Chaetomium Globosum ND35

At present,physical treatment,seed coating,chemical treatment and seed priming are mostly used to deal with seed before germination in vegetable facility cultivation,which greatly reduces seedling stage diseases and improves seedling quality.It has been widely used on various crops.However,there are few studies on the use of fungal plant endophytes that can coexist with plants in treatment of seeds.In order to provide a reference for increasing the comprehensive application of fungal biocontrol agent on plants.In this experiment,cucumber"Jinchun No.4"was used as the test material to study the effect of Chaetomium globosum ND35 on seed germination and seedling growth of cucumber in this experiment.First,the appropriate C.globosum ND35 spore suspension concentration that affects the germination vigor of cucumber seeds was selected.Secondly,the optimal concentration of C.globosum ND35 spore suspension was furtherly determined for seed germination,protective enzyme activity,active oxygen content,endogenous hormone changes,and transcriptome analysis and influence of the regulated growth promoting factors.Finally,the solid fermentation of the endophytic fungus C.globosum ND35 was explored and applied to cucumber seedlings to verify its growth promoting effect.The main results of the study are as follows:?1?The results of germination test of cucumber seeds with different concentrations of C.globosum ND35 spore suspension showed that the best concentration C.globosum ND35was 1×10⁶ cfu/mL,which had the best effect on germination growth of cucumber seeds.The germination energy,germination index,vigor index of germination potential increased by56.94%,19.92%,100.12%,respectively.After 48 hours of germination,germination rate of cucumber seeds reached 100%,root length increased by 117.18%,and lateral roots and capillary roots increased significantly.?2?The changes of protective enzyme activity,active oxygen content,and endogenous hormones during cucumber germination showed that 1×10⁶ cfu/mL of C.globosum ND35treatment increased the protective enzyme activity,maintained the physiological range of active oxygen and stimulated the synthesis of endogenous hormones content.When the cucumber seeds were treated for 36 h,the activities of peroxidase?POD?and phenylalanine ammonia lyase?PAL?increased by 53.64%and 10.33%,reactive oxygen species?ROS?and hydrogen peroxide?H₂O₂?were within the physiological range and increased by 20.99%and26.72%.Plant endogenous gibberellin?GA?,indole-3-acetic acid?IAA?,salicylic acid?SA?,jasmonic acid?JA?content increased by 34.20%,33.62%,40.07%,15.61%,respectively.?3?Through the analysis of transcriptome sequencing,the differentially expressed genes induced by C.globosum ND35 in cucumber seed germination were obtained,and the differentially expressed genes related to seed germination were screened by genomic comparison.During C.globosum ND35 treatment,there were 6338 differential expression genes,including 76 differentially expressed genes at 24 h,288 differentially expressed genes at 30 h,452 differentially expressed genes at 36 h,2037 differentially expressed genes at 48 h,and 706 differentially expressed genes at 60 h.GO and KEGG two databases were used to annotate the functions and metabolic pathways of differentially expressed genes.Plant hormone transduction,phenylalanine ammonia lyase activity,oxidoreductase activity,microtubule motor activity,photosynthesis,oxidoreductase process,metabolism of glyceraldehyde 3-phosphate and other pathways of cucumber seed were mainly affected to promote seed germination..The molecular function and role of C.globosum ND35 was revealed in promoting seed germination of plant.?4?Solid fermentation formula for C.globosum ND35 strain was screened by single factor and orthogonal test.The results showed that begonia wood chips were used as fermentation medium,with 20%organic fertilizer,60%water,and 8%inoculation content of1×10⁶ cfu/mL of C.globosum ND35 spore suspension,incubation for 20 days,60%of volume occupied fermentation material and initial stirring material at the 12th day.C.globosum ND35 solid fermentation had the most spore production.The key factors were obtained for optimized combination formula by orthogonal test.They are 80%of begonia wood chips,20%of organic fertilizer,containing 65%water content and 8%inoculation with1×10⁶ cfu/mL of C.globosum ND35 suspension spore.The spore production of C.globosum ND35 reached up to 8.86×10⁸ cfu/g for 20 days of cultivation in the dark.?5?Effect of C.globosum ND35 seedling substrate on cucumber seedling growth was investigated.The results showed that the seedling substrate containing 1×10⁶ cfu/g of C.globosum ND35 seedling substrate has the best effect on cucumber seedling emergence and growth promotion.Root/shoot ratio,strong seedling index,G value increased by 45.45%,60.60%,57.14%,respectively.Cucumber root activity increased by 126.67%.Chlorophyll a,b content increased by 53.94%,25.58%.