小麦、玉米两熟秸秆还田土壤中6种有机酸对小麦纹枯病的化感作用

【目的】冬小麦、夏玉米一年两熟是中国北方最广泛的农作制度,中国北方小麦、玉米生产普遍采用秸秆还田的耕作方式,关于秸秆还田对小麦土传病害的影响一直存在争议。通过分析不同秸秆还田年限地块耕层土壤中的主要有机酸对小麦幼苗生长、禾谷丝核菌(Rhizoctonia cerealis)及纹枯病发生的化感作用,明确我国北方冬小麦、夏玉米一年两熟种植体系下秸秆还田对小麦纹枯病发生的影响。【方法】利用GC-MS技术分析玉米秸秆还田地块耕层土壤乙酸乙酯提取物中化学物质的种类与含量,并分别用氯化三苯基四氮唑(TTC)还原法、电导率法、氮蓝四唑光化(NBT)还原法和愈创木酚比色法测定含量较高的6种有机酸对小麦幼苗根系活力、根系细胞膜透性、超氧化物歧化酶(SOD)和过氧化物酶(POD)活性的影响,用常规方法测定其对禾谷丝核菌和纹枯病发生的影响。【结果】秸秆还田地块耕层土壤中含有机酸、烷烃、醇、酰胺及醛类等化学物质,相对含量分别为45.45%、17.70%、17.08%、6.12%和5.44%;含量较高的有机酸类物质包括邻羟基苯甲酸(9.24%)、3-苯基-2-丙烯酸(4.12%)、对羟基苯甲酸(3.21%)、4...

Allelopathy of Six Organic Acids on Wheat Sheath Blight in the Soil of Winter Wheat-Summer Maize Double Cropping Straw Returning System

【Objective】Double cropping of winter wheat and summer maize is the most extensive farming system in northern China. Straw returning has been widely used in wheat and maize production. But, the effect of straw returning on the occurrence of soil borne diseases of wheat has been controversial. The objective of this study is to analyze the main chemical constituents in the cultivated-layer soil with different straw returning years and the allelopathic effects of the main organic acids on the growth of wheat seedlings, the mycelium growth and sclerotia formation of Rhizoctonia cerealis and occurrence of wheat sheath blight (WSB), and to understand the relationship between straw returning and WSB incidence.【Method】Gas chromatography-mass spectrometry (GC-MS) technique was used to analyze the types and contents of chemical substances in the extract of ethyl acetate from the cultivated soil where maize straw returning, and the effects of 6 organic acids with higher content on the root activity, root cell membrane permeability, superoxide dismutase (SOD) and peroxidase (POD) activity of wheat seedlings were determined with the TTC reduction, electrical conductivity, NBT photoreduction and guaiacol colorimetry methods, respectively. Meanwhile, the effects of these organic acids on the mycelium growth, sclerotium formation and occurrence of WSB were determined by the conventional methods.【Result】The relative contents of organic acids, alkanes, alcohols, amides, and aldehydes in the cultivated-layer soil and straw returning were 45.45%, 17.70%, 17.08%, 6.12%, and 5.44%, respectively. Organic acids mainly included o-hydroxybenzoic acid (9.24%), 3-phenyl-2-acrylic acid (4.12%), p-hydroxybenzoic acid (3.21%), 4-hydroxy-3,5- dimethoxybenzoic acid (2.26%), heneicosanoic acid (1.88%), 4-methoxy-anthranilic acid (1.73%), 8-octadecanoic acid (0.76%) and 3-(4-hydroxy-3- methoxyphenyl)-2-acrylic acid (0.52%). 4-methoxy-anthranilic acid and 3-(4-hydroxy-3-methoxyphenyl)-2-acrylic acid at 0.08-10.0 μg·mL^-1had significant promoting effects on mycelial growth (expect 4-methoxy-anthranilic acid at 10.0 μg·mL^-1), dry weight and sclerotium formation of R. cerealis, and the relative content of the two substances increased with the extension of straw returning years. O-hydroxybenzoic acid significantly promoted mycelial growth and sclerotia formation of R. cerealis at 0.4 and 0.08 μg·mL^-1. In contrast, 50.0 μg·mL^-1 of o-hydroxybenzoic acid and 4-hydroxyl-3-methoxy-benzoic acid, and 0.4-50.0 μg·mL^-1 of benzoic acid all showed inhibitory effects. All 6 organic acids at concentrations of 2.0-5.0 μg·mL^-1 inhibited the growth of wheat seedlings in a dose-dependent manner. The inhibitory effect of p-hydroxybenzoic acid was the strongest, followed by o-hydroxybenzoic acid, and 4-methoxy-anthranilic acid was the weakest. 3-(4-hydroxy-3-methoxyphenyl)-2-acrylic acid, 4-methoxyanthranilic acid, o-hydroxybenzoic acid, and p-hydroxybenzoic acid at concentrations of 0.4-50.0 μg·mL^-1 aggravated the occurrence of WSB. 3-(4-hydroxy-3-methoxyphenyl)-2-acrylic acid had the strongest enhancing effect, with the incidence and disease index increased by 49.0% and 46.7%, respectively. Benzoic acid and 4-hydroxy-3-methoxyphenyl-benzoic acid had no significant effect on the occurrence of WSB.【Conclusion】Organic acids, esters, hydrocarbons, amides, and aldehydes were found in the cultivated-layer soil in the winter wheat-summer maize double cropping straw returning system. Organic acids were the most abundant of those chemicals. 3-(4-hydroxy-3-methoxyphenyl)-2-acrylic acid, 4-methoxyanthranilic acid, o-hydroxybenzoic acid, and p-hydroxybenzoic acid at a certain concentration can promote the occurrence of WSB. 3-(4-hydroxy-3-methoxyphenyl)-2-acrylic acid has the strongest stimulatory effect, while benzoic acid and 4-hydroxy-3-methoxy-benzoic acid have no effect on the occurrence of WSB. Allelopathic effects of organic acids in the cultivated-layer soil, including the promotion on pathogen growth and inhibition on physiological activity and growth of wheat roots, may be one of the main reasons for the serious occurrence of WSB in the straw returning region in northern China.