Effects Of Silicon And Molybdenum On Stress Resistance And Fruit Quality Of Peach Trees

Drought and low temperature are important factors affecting the production of peach trees.And with the global climate change,extreme weather occurs frequently,posing a serious threat to the production of fruit trees.Gummosis in peach is widespread and serious damage,and is closely related to environmental stress.Silicon and molybdenum fertilizers have been increasingly studied on the growth and development of gramineous plants,disease control and their mechanisms,but little has been reported on their effects on peach tree production.Therefore,in this experiment,peach seedlings were used as test materials to study the effects of silicon and molybdenum on seedling growth and stress resistance under drought and low temperature stress;And the isolated shoots of ‘Chun xue’and fruits of ‘Rui pan 21’ in mature peach trees were used to study the effects of silicon on the gummosis in peach;The effects of silicon and molybdenum on the quality of peach fruit were studied with the12-year-old ‘Luxing’.In order to provide theoretical support and technical support for the use of silicon and molybdenum fertilizer in peach production.The main results of research were as follows:1.Silicon decreased the rate of gummosis,reduced the expression level of Pp ACS1 and reduced the enzyme activity of polygalacturonase.Silicon up-regulated the expression level of Pp SAMDC and increased the content of spermidine and spermine,which inhibited the rate of endogenous ethylene synthesis,thus silicon-mediated PAs inhibited ETH synthesis.It was further discovered that Si regulated the gene expression of Pp ERF21 and Pp ERF27.Yeast one-hybrid and dual-luciferase reporter assays showed that Pp ERF21 and Pp ERF27,through direct interaction with the promoter of Pp PG1,inhibited the transcriptional activation of Pp PG1.Overexpression of Pp ERF21 and Pp ERF27 inhibited the enzymatic activity of PG effectively and reduced fruit colloid production when bacterial cells harbouring the expression vector were used to instantaneously infect peach fruit.These results showed that Si inhibiting the synthesis of ETH by promoting PAs synthesis,mediating Pp ERF21 and Pp ERF27 expression to inhibit the expression of Pp PG1,thereby inhibiting gummosis in peach.2.Under drought stress,silicon addition improved the water use efficiency,antioxidant capacity,and net photosynthetic rate,inhibited of stomatal closure caused by water stress,and enhanced drought resistance.A comparative transcriptome analysis identified a total of 2275 genes that respond to silicon under drought stress.These genes were mainly involved in ion transport,hormone and signal transduction,biosynthetic and metabolic processes,stress and defence responses and other processes.We analysed the effects of silicon on the modulation of stress-related hormonal crosstalk and amino acid and sugar metabolism.The results showed that silicon promotes zeatin,gibberellin,and auxin biosynthesis,inhibits the synthesis of abscisic acid,then promotes lateral root development and inhibits stomatal closure,and regulates the signal transduction of auxin,cytokinein,gibberellin and salicylic acid.Silicon also regulates the metabolism of various amino acids and promotes the accumulation of sucrose and glucose to improve drought resistance of peach seedlings.3.Under drought stress,the water content,chlorophyll content and proline content of peach seedlings leaves treated with ammonium molybdate significantly higher than control group,and the electrolyte leakage was lower than it,preferably to 0.04% ammonium molybdate results;As compared to the control,the expression of Pp LOS5/ABA3 in the leaves treated with 0.04% ammonium molybdate was significantly increased,the ABA content,water use efficiency,and the net photosynthetic rate were higher than control group,the transpiration rate was lower than control group;antioxidant enzyme activity increased significantly and MDA content decreased significantly in the leaves;the water loss rate of isolated leaves was reduced.The results indicate that,peach seeding treated with ammonium molybdate can increase the content of ABA and proline,increase the activity of antioxidant enzyme,relieves cell membrane oxidation damage,decrease rate of water loss of leaves,alleviate the damage of the drought stress,through regulating the expression of drought-resistant genes,and then increase the drought resistance of the plant.4.Under low temperature stress,as compared to water treatment,the frost index and the conductivity of peach seedlings leaves treated with different concentrations of ammonium molybdate were significantly decreased;the SPAD and net photosynthetic rate decrease retard;proline and soluble sugar content significantly improved,preferably to 0.04% results.Further,the expression of Pp LOS5/ABA3,Pp P5CS1 and Pp RCI3 was significantly increased;the activities of catalase,peroxidase and superoxide dismutase were significantly increased,the malondialdehyde content was significantly decreased.Peach seeding treated with ammonium molybdatecanincrease the content of soluble sugar,proline and the activity of antioxidant enzyme,relieves cell membrane oxidation damage,and then alleviate the damage of the low temperature stress.5.Silicon and molybdenum treatment increased the chlorophyll content,enhanced photosynthesis of peach leaves;at the same time,increased the single fruit weight and fruit shape index,increased the content of soluble solids and vitamin C of peach fruit,and effectively improve the fruit quality.