不同连作年限马铃薯根系分泌物的成分鉴定及其生物效应

Identification of chemicals in potato root exudates under different years of continuous cropping and their biologic effects

为探讨马铃薯连作障碍的可能机理,在大田条件下,收集连作1～5 a(CP1-CP5)马铃薯植株的根系分泌物,采用GC-MS对根系分泌物的主要成分进行了鉴定,并通过生物检测验证了根系分泌物的生物效应。结果表明:CP1-CP5鉴定出的物质主要有酸类、糖类、胺类、醇类、酯类和嘧啶类,但各类物质的数量和含量不同。CP1-CP5中均鉴定出棕榈酸,相对含量分别为0.55%、0.87%、1.24%、1.05%和0.95%,浓度分别为7.12 mg×L^(-1)、7.39 mg×L^(-1)、9.46 mg×L^(-1)、8.38 mg×L^(-1)和8.02 mg×L^(-1)。马铃薯根系分泌物显著抑制了马铃薯的生长,抑制作用随连作年限延长而增强。棕榈酸对马铃薯生长的抑制表现出明显的浓度效应,随浓度升高而增强。马铃薯根系分泌物明显促进了立枯丝核菌的生长,菌落直径和菌丝鲜质量表现为CP3最高,CP1最低,CP2、CP4和CP5之间没有显著差异。棕榈酸明显促进了立枯丝核菌的生长,随着棕榈酸浓度的增加,菌落直径和菌丝鲜质量先增加再减小, 10 mg×L^(-1)棕榈酸的菌落直径和菌丝鲜质量最大。由此说明,随马铃薯连作年限延长,根系分泌物的毒性越强;马铃薯根系分泌物对立枯丝核菌的促进作用加剧了马铃薯的连作障碍,棕榈酸是马铃薯根系分泌的化感自毒物质。

In order to explore possible obstruction mechanisms in continuous potato cropping systems,potato root exudates were collected in 1–5 years(CP1-CP5)continuous cropping systems of potato under field conditions.Chemical composition of root exudates was determined by the GC-MS method and biological effects of the exudates were detected by biological monitoring.The results showed that the main components of potato root exudates in CP1-CP5 treatments included organic acids,glucides,amines,alcohols,esters and pyrimidines,although the chemicals occurred in different quantities and contents.Palmitic acid occurred in all the CP1-CP5 systems,with relative contents of 0.55%,0.87%,1.24%,1.05%and 0.95%,and concentrations of 7.12mg·L^-1、7.39mg·L^-1、9.46mg·L^-1、8.38mg·L^-1 and 8.02 mg·L^-11,respectively.Biological analyses showed that potato root exudates significantly inhibited potato growth,with inhibition expression of CP5>CP4>CP3>CP2>CP1.The inhibition of potato growth by palmitic acid had obvious concentration effects,with inhibition expression of 100 mg·L^-1>50 mg·L^-1>10 mg·L^-1>5 mg·L^-1.Potato root exudates obviously promoted the growth of Rhizoctonia solani.The colony diameter and mycelia fresh weight of R.solani were highest in CP3 and lowest in CP1.No significant differences were observed between CP2,CP4 and CP5.Palmitic acid promoted the growth of R.solani.The colony diameter and mycelia fresh weight of R.solani increased firstly and then later decreased along with increasing concentration of palmitic acid.Colony diameter and mycelia fresh weight of R.solani were highest at 10 mg·L^-1.The study showed that potato root exudates significantly inhibited potato growth,and the inhibiting effect increased with increasing number of years of continuous cropping.The promotion of potato root exudates to R.solani growth exacerbated the obstacles of continuous cropping.Palmitic acid is the allelochemicals secreted by potato roots.