断根与打顶对番茄嫁接愈合的抑制作用

Inhibiting Eeffect of Root-Cutting and Top-Pinching on Graft Healing of Tomato

【目的】断根嫁接苗和打顶双干或多干嫁接苗日益广泛用于番茄栽培,丰产作用显著。了解断根与打顶对番茄嫁接愈合的作用机制,可为番茄嫁接生产提供理论依据。【方法】以‘硬粉8号’为接穗品种,‘砧爱1号’为砧木品种,观测断根和打顶后番茄嫁接愈合进程、成活率和木质部连通性等,同时测定嫁接接合部生长素和细胞分裂素的含量及愈合相关基因的表达。【结果】断根和打顶抑制了嫁接接合部上方木质部分化基因VND7的表达,并显著延迟了木质部的重构。断根显著降低了嫁接后12和72 h接合部玉米素核苷(tZR)和反式玉米素(tZ)的含量,以及嫁接后12 h接合部吲哚-3-乙酸(IAA),吲哚-3-乙酸甲酯(ME-IAA)和吲哚-3-甲醛(ICAld)的含量;打顶嫁接后12 h接合部IAA和ME-IAA含量显著低于对照和断根处理,下调了嫁接后3和12 h接合部上方和下方韧皮部分化相关基因NEN4表达水平。断根或打顶均下调了嫁接后3—48 h接合部上方细胞分裂相关基因Histone H4和SlcycB1-4的表达水平;断根和打顶同时处理使嫁接接合部IAA和ME-IAA含量显著低于断根处理,使tZR和tZ的含量及木质部连通性显著低于打顶处理。打顶和断根后分别在嫁接接合部施用10mmol·L;IAA和10 mmol·L;6-BA可显著促进嫁接苗木质部的重构。【结论】断根和打顶分别降低接合部细胞分裂素和生长素积累,下调愈合相关基因表达,降低木质部输导能力,进而延缓番茄嫁接愈合进程。

【Objective】The root-cutting grafting seedlings and top-pinching double-stem grafting seedlings or multi-stem grafting seedlings have been widely used in tomato cultivation,which have significant effects on high yield.Understanding the mechanism of root-cutting and top-pinching on tomato graft healing could provide the theoretical basis for tomato grafting production.【Method】Using‘YingFen No.8’as scion and‘ZhenAi No.1’as rootstock,the grafting healing process,survival rate and xylem connectivity of tomato after root-cutting and top-cutting were observed,and the contents of auxin and cytokinin as well as the expressions of healing related genes in the grafted part were measured.【Result】Root-cutting and top-pinching inhibited the expression of xylem differentiation gene VND7 above the graft union,and significantly delayed xylem remodeling.The root-cutting treatment significantly decreased the contents of trans-Zeatin riboside (tZR) and trans-Zeatin (tZ) at 12 and 72 hours after grafting,as well as the contents of indole-3-acetic acid (IAA),methyl indole-3-acetate (ME-IAA) and indole-3-carboxaldehyde (ICAld) at12 hours after grafting.The contents of IAA and ME-IAA at 12 hours after top-pinching grafting were significantly lower than those of the control and root-cutting treatment,and the expression level of the phloem differentiation related gene NEN4 at 3 and 12hours after grafting was down-regulated.Root-cutting or top-pinching down-regulated the expression levels of cell division related genes Histone H4 and SlcycB1-4 above the graft union at 3-48 hours after grafting.Under root-cutting and top-pinching treatment,the contents of IAA and ME-IAA in grafting union were significantly lower than those under root-cutting treatment,and the contents of tZR and tZ and xylem connectivity were significantly lower than those under top-pinching treatment.The application of10 mmol·L;IAA and 10 mmol·L;6-BA at the grafted union after top-pinching and root-cutting could significantly promote the xylem remodeling of grafted seedlings.【Conclusion】In conclusion,root-cutting and top-pinching could reduce the accumulation of cytokinin and auxin,down-regulate the expression of genes related to healing,reduce xylem transduction capacity,and delay the process of tomato grafting healing.