CN108680662A - A kind of wheat-broadbean intercropped inhibits the assay method of faba bean Fusarium wilt - Google Patents

Abstract

The invention belongs to the technical field of general botany and discloses a method for measuring the inhibition of broad bean wilt by wheat and broad bean intercropping. The method for determining the inhibition of broad bean wilt by wheat and broad bean intercropping comprises: soil cultivation and pathogenic bacteria of wheat and broad bean intercropping and broad bean monoculture inoculation; collection of rhizosphere soil and root exudates and disease investigation; determination of sugars, amino acids and organic acids in root exudates; effects of root exudates on spore germination, mycelial growth and sporulation of Fusarium wilt pathogen. The invention helps to explain the mechanism of intercropping to control soil-borne diseases, improves crop productivity by using intercropping, enhances farmland biodiversity and farmland ecological stability, realizes high grain yield and environmental friendliness, and reduces the negative impact of chemical fertilizers and pesticides on the environment , It has important guiding significance and application value to promote the increase of farmers' production and income and the sustainable development of agriculture.

Description

A method for determining the inhibition of broad bean wilt by wheat and broad bean intercropping

technical field

The invention belongs to the technical field of general botany, and in particular relates to a method for determining the suppression of broad bean wilt by wheat and broad bean intercropping.

Background technique

At present, the existing technologies commonly used in the industry are as follows: the pursuit of large-scale planting of single crops in modern agriculture and the extensive application of pesticides and chemical fertilizers make farmland ecosystems increasingly simple and fragile, resulting in frequent occurrence of crop diseases and shorter and shorter disease epidemic cycles, resulting in Crop production is reduced, and it also causes serious problems such as the continuous depletion of non-renewable resources and environmental pollution. As the essence of traditional agriculture in my country, intercropping has the advantages of increasing production and improving the efficiency of nutrient resource utilization. It is also an effective way to continuously control diseases and insect pests and enhance the ecological stability of farmland by using biodiversity. At present, the use of intercropping of different crops to improve the ecological stability of farmland, increase the biodiversity of farmland, improve the productivity of farmland ecosystem, and continuously control diseases and insect pests has become one of the key issues studied by scientists all over the world. Broad bean is an important leguminous crop in the world. It has the characteristics of food, vegetables, feed and green manure, and has a high nitrogen fixation capacity due to its wide adaptability. It is planted in more than 70 countries around the world, with a planting area of up to 260. million hectares. China's broad bean planting area and output rank first in the world. The broad bean planting area reaches 1.05 million hectares, accounting for 59% of the world's planting area, and its total output accounts for 61% of the world's total broad bean production. China's broad bean planting situation and production level affect and determine the world's broad bean production. For a long time, many studies have studied the mechanism of intercropping disease control (airborne diseases) and increased production from the aspects of collocation mode of faba bean and other crops, utilization of aboveground light and heat resources, efficient absorption of nutrients, changes of pathogenic bacteria and disease-resistant substances, and significant progress has been made. . However, there are few studies on the mechanism of intercropping between broad bean and other crops to control soil-borne diseases, and the influence of underground rhizosphere interaction on rhizosphere microecology in the intercropping system of broad bean and other crops and its role in the control of soil-borne diseases The research on the role of the root system has just started, especially the interaction mechanism between the underground root exudates and the suppression of soil-borne diseases in the leguminous and gramineous intercropping systems is still lacking a systematic understanding. Clarifying these issues is not only conducive to a deep understanding of the mechanism of rational intercropping to increase yield and crop disease resistance, but also has great significance for revealing the interaction mechanism of above-ground and below-ground biodiversity.

In summary, the problems in the prior art are:

(1) The existing technology lacks understanding of the inhibitory effect of root exudates on faba bean wilt in wheat and broad bean intercropping systems, resulting in low intercropping productivity and low grain yield.

(2) A large amount of chemical fertilizers and pesticides are used, which pollutes the environment; it is not conducive to increasing farmers' production and income and sustainable agricultural development.

The difficulty and significance of solving the above-mentioned technical problems: it is not only conducive to in-depth understanding of the mechanism of rational intercropping to increase yield and crop disease resistance, but also has great significance for revealing the mechanism of above-ground and below-ground biodiversity interaction.

Contents of the invention

Aiming at the problems in the prior art, the invention provides a method for determining the inhibition of broad bean wilt by wheat and broad bean intercropping.

The present invention is realized in this way, a kind of measuring method of suppressing broad bean wilt by wheat broad bean intercropping, the measuring method of described wheat broad bean intercropping suppressing broad bean wilt comprises: the soil cultivation of wheat broad bean intercropping and broad bean single cropping and the inoculation of pathogenic bacteria; Collection of rhizosphere soil and root exudates and disease investigation; determination of sugars, amino acids and organic acids in root exudates; effects of root exudates on spore germination, mycelial growth and sporulation of Fusarium wilt pathogen.

Further, the first step specifically includes: the size of the pot body is 14×20 cm, and each pot is filled with 2.5 kg of soil; the planting density of wheat and broad beans is: 4 seedlings are reserved in each pot for single-cropping broad beans, 2 seedlings for wheat and broad beans intercropping, and 2 seedlings for wheat and broad beans. Four seedlings were inoculated with the pathogenic bacteria of broad bean wilt at the five-leaf stage of broad beans, and no pesticides, fungicides and insecticides were used for seedling management.

Further, said step two specifically includes:

Collection method of rhizosphere soil extract solution: use soil shaking method to remove non-rhizosphere soil, extract rhizosphere soil solution with 100ml distilled water, centrifugally filter, filter the filtrate through a 0.45 μm filter membrane, and store it frozen at -20C for later use;

Root exudates: Take the roots of broad bean monocropping and wheat broad bean intercropping respectively, wash the roots repeatedly with tap water, and then wash them with distilled water 5 times, soak them in 5 mg/L thymol for 3 minutes, and put them in 0.005mol.L ^-1 CaCl ₂ solution The root exudates were collected by ventilation for 2 hours, and the collected solution was evaporated to dryness in a small rotary at 40 degrees Celsius to 10 ml for later use.

Further, in the disease investigation in the step 2, record the grading standard, incidence rate and disease index;

The degree of disease is divided into 5 grades: Grade 0: no lesion at the base of the stem and roots, and apparently asymptomatic; Grade 1: slight lesion or discoloration at the base of the stem or root; grade 2: disease at the base of the stem or the main lateral root Spots, but not contiguous: Grade 3: Lesions, discoloration or rot appear on 1/3-1/2 of the base of the stem or root, and the lateral roots are significantly reduced; Grade 4: The base of the stem is surrounded by lesions or most of the roots are discolored and rotten; Grade 5: The plant withers and dies.

Further, the incidence rate in the step 2=(number of diseased strains/total number of investigated strains)×100;

Disease index = ∑ (number of diseased plants at all levels × corresponding level value) / (highest level value × total number of investigated plants) × 100.

Further, in the determination of sugar, amino acid and organic acid in root exudates in the step three, the centrifuge tube is taken out from the refrigerator to thaw and pass through the membrane; the determination of total sugar content is carried out by anthrone colorimetry, and the amino acid analysis is carried out by automatic amino acid analysis Determination by instrument; determination of organic acid components and content of root exudates using high-performance liquid chromatography, the condition is 250mm×4.6mm C18 reverse phase column, mobile phase 25mmol.L ^-1 KH ₂ PO ₄ , flow rate 1mL.min ^-1 , the temperature is 31° C., the measurement wavelength is 214 nm, and the injection volume is 20 μL.

Another object of the present invention is to provide a kind of wheat and broad bean intercropping planting method that suppresses the determination method of broad bean wilt by said wheat broad bean intercropping: keep the current cultivation mode and plant spacing, row spacing and density of wheat and broad bean, on the same big field , 7-10 rows of wheat are planted on the soil surface, and 2-4 rows of broad beans are planted on the soil moisture side. The row spacing between the broad beans and the wheat is 10-30cm, and the broad beans are sown earlier than the wheat.

In summary, the advantages and positive effects of the present invention are:

(1) The present invention studies the interaction between root exudate-soil microorganism-pathogen in the wheat broad bean intercropping system and its interaction with crop disease resistance, from the soil cultivation of wheat broad bean intercropping and broad bean monocropping and the inoculation of pathogenic bacteria Departure; collection of rhizosphere soil and root exudates and disease investigation; determination of sugars, amino acids and organic acids in root exudates and effects of root exudates on spore germination, mycelial growth and sporulation of Fusarium wilt pathogen The determination of root exudates in wheat and broad bean intercropping system reveals the inhibitory effect of root exudates on broad bean wilt; for the first time, the interaction mechanism between root exudates in wheat and broad bean intercropping system and crop disease resistance is revealed from the underground interaction; and it helps It can be used to explain the mechanism of intercropping to control soil-borne diseases, improve crop productivity, enhance farmland biodiversity and farmland ecological stability by using intercropping.

(2) It has important guiding significance and application value to achieve high grain yield and environmental friendliness, reduce the negative impact of chemical fertilizers and pesticides on the environment, and promote farmers' increase in production and income and sustainable agricultural development.

(3) The planting method of the wheat and broad bean intercropping system of the present invention improves the yield of wheat and broad bean by 30% compared with the prior art, and greatly increases farmers' income.

Description of drawings

Fig. 1 is a flow chart of a method for determining the inhibition of broad bean wilt by wheat and broad bean intercropping provided in an embodiment of the present invention.

Fig. 2 is a schematic diagram of the quantity of organic acids in the root system of broad bean in single intercropping after inoculation of pathogenic bacteria provided by the embodiment of the present invention.

Fig. 3 is a schematic diagram of the effect of exogenous phenolic acids on the germination of spores of the pathogenic fungus of broad bean wilt provided by an example of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The invention discloses the inhibitory effect of the root exudates in the wheat and broad bean intercropping system on faba bean wilt through the interaction of root exudates-soil microorganisms-pathogens in the wheat and broad bean intercropping system and the interaction with crop disease resistance.

As shown in Figure 1, the assay method that wheat broad bean intercropping that the embodiment of the present invention provides suppresses broad bean wilt comprises the following steps:

S101: Soil cultivation of wheat and broad bean intercropping and broad bean monoculture and inoculation of pathogenic bacteria;

S102: Collection of rhizosphere soil and root exudates and disease investigation;

S103: Determination of sugars, amino acids and organic acids in root exudates;

S104: Effects of root exudates on spore germination, hyphal growth and sporulation of Fusarium wilt pathogen.

In step S101: Soil cultivation of wheat broad bean intercropping and broad bean monoculture and inoculation of pathogenic bacteria

The size of the test pot is 14x20cm, and each pot is filled with 2.5kg of soil; planting density of wheat and broad beans: 4 seedlings per pot for single-cropping broad beans, 2 seedlings for wheat and broad bean intercropping, 4 seedlings for wheat, inoculated at the five-leaf stage of broad beans The pathogenic bacteria of broad bean wilt, the whole seedling stage is managed according to the routine, no pesticides, fungicides and insecticides are used; Effects on functional diversity.

In step S102: collection of rhizosphere soil and root exudates and disease investigation

Collection method of rhizosphere soil extract solution: Shake the soil to remove non-rhizosphere soil, extract the rhizosphere soil solution with 100ml of distilled water, rapidly centrifuge and filter, pass the filtrate through a 0.45μm filter membrane, and store it in a freezer at -20°C for later use.

Root exudates: Take the roots of broad bean monocropping and wheat broad bean intercropping respectively, wash the roots repeatedly with tap water, and then wash them with distilled water 5 times, soak them in 5 mg/L thymol for 3 minutes, and put them in 0.005mol.L ^-1 CaCl ₂ solution Ventilate and collect root exudates for 2 hours, and the collected solution is evaporated to dryness in a small rotary at 40 degrees Celsius to 10ml for later use;

In step S102: the disease investigation is to investigate the occurrence of diseases every 7-8 days from the day when the broad bean seedlings were inoculated with pathogenic bacteria, and record the grading standard, incidence rate and disease index;

The degree of disease is divided into 5 grades: Grade 0: no lesion at the base of the stem and roots, and apparently asymptomatic; Grade 1: slight lesion or discoloration at the base of the stem or root; grade 2: disease at the base of the stem or the main lateral root Spots, but not contiguous: Grade 3: Lesions, discoloration or rot appear on 1/3-1/2 of the base of the stem or root, and the lateral roots are significantly reduced; Grade 4: The base of the stem is surrounded by lesions or most of the roots are discolored and rotten; Level 5: Plant withers and dies;

Incidence rate = (number of diseased plants/total number of surveyed plants) × 100;

Disease index = ∑ (number of diseased plants at all levels × corresponding level value) / (highest level value × total number of investigated plants) × 100.

In step S103: the determination of sugars, amino acids and organic acids in root exudates, during the determination, take out the centrifuge tube from the refrigerator to thaw and pass through the membrane (0.25 μm); the determination of the total sugar content is carried out by anthrone colorimetry, and the amino acid analysis is carried out Determination of amino acid automatic analyzer. The components and content of organic acids in root exudates were determined by high-performance liquid chromatography with a 250 mm × 4.6 mm C18 reversed-phase column (Altima C-18), a mobile phase of 25 mmol.L ^-1 KH2PO4 (pH 2.25), and a flow rate of 1 mL. min ^-1 , the temperature is 31°C, the measurement wavelength is 214nm, and the injection volume is 20μL.

In step S104: obtained through data analysis: the influence of broad bean monocropping and intercropping root exudates on the spore germination, mycelial growth and sporulation of broad bean wilt pathogen (the broad bean wilt pathogen), evaluate the effect of intercropping root exudates on broad bean wilt Inhibitory effect of pathogenic bacteria.

The application effects of the present invention will be described in detail below in conjunction with specific embodiments.

Example 1

1, the assay method that wheat broad bean intercropping that the embodiment of the present invention provides suppresses broad bean wilt comprises:

1) Soil cultivation of wheat broad bean intercropping and broad bean monoculture and inoculation of pathogenic bacteria

Soil culture test of wheat and broad bean intercropping and broad bean single cropping: the test pot size is 14×20cm, and each pot is filled with 2.5kg of soil (the non-continuous cropping soil of broad bean is collected in the field, and the basic agrochemical properties of the soil are organic matter content of 23.2g.kg ^-1 , total nitrogen 1.90g.kg ^-1 , alkaline hydrolyzed nitrogen 119.0mg.kg ^-1 , available phosphorus 56.5mg.kg ^-1 , available potassium 123.4mg.kg ^-1 , pH value 6.4); wheat broad bean planting density: single 4 seedlings per pot for broad beans, 2 seedlings for wheat broad bean intercropping broad beans, 4 wheat seedlings (for the test species: wheat: Yunmai 47, broad bean: Yundou 8363); the seeds are pretreated before sowing;

Inoculate broad bean fusarium wilt pathogenic bacteria at the five-leaf stage of broad beans (the pathogenic bacteria before inoculation need to be cultivated by conventional means). The whole seedling stage is managed according to routine, without using pesticides, fungicides and insecticides.

2) Collection of rhizosphere soil and root exudates and disease investigation

Collection method of rhizosphere soil extract solution: Shake the soil to remove non-rhizosphere soil, extract the rhizosphere soil solution with 100ml of distilled water, rapidly centrifuge and filter, pass the filtrate through a 0.45μm filter membrane, and store it in a freezer at -20°C for later use.

Root exudates: Take the roots of broad bean monocropping and wheat broad bean intercropping respectively, wash the roots repeatedly with tap water, and then wash them with distilled water 5 times, soak them in 5 mg/L thymol for 3 minutes, and put them in 0.005mol.L ^-1 CaCl ₂ solution Ventilate and collect root exudates for 2 hours, and the collected solution is evaporated to dryness in a small rotary at 40 degrees Celsius to 10ml for later use;

The disease investigation is to investigate the occurrence of the disease every 7-8 days from the day when the broad bean seedlings are inoculated with pathogenic bacteria, and record the grading standards, incidence rate and disease index for data statistics; the degree of disease is divided into 5 levels: level 0: stem base and No lesions on the root, apparently asymptomatic; Grade 1: Slight lesion or discoloration at the base of the stem or part of the root; Grade 2: Lesions at the base of the stem or main lateral roots, but not contiguous: Grade 3: 1/3 -1/2 of the base of the stem or root appears lesion, discoloration or rot, and the lateral roots are significantly reduced; grade 4: the base of the stem is surrounded by lesion or most of the root system is discolored and rotten; grade 5: the plant withers and dies;

Incidence rate (%) = (number of diseased plants/total number of surveyed plants) × 10

Disease index (%) = ∑ (number of diseased plants at all levels × corresponding level value) / (highest level value × total number of investigated plants) × 100;

After being inoculated with the pathogenic bacteria of faba bean wilt, the single intercropping broad bean began to show symptoms on the 16th day. By the 29th day, the incidence rates of faba bean wilt were 88.3% and 83.3%, respectively, and the disease index was 60.42% and 56.2%, respectively. Compared with monocropping, intercropping reduced the incidence of Fusarium wilt by 8.9% and the disease index by 12% on average; it shows that under the condition of inoculating pathogenic bacteria, intercropping can still reduce the incidence and disease index of Fusarium wilt to a certain extent.

Table 1 Incidence and disease index of broad bean wilt in single intercropping

The reduction effect of intercropping on the pathogenic bacteria of faba bean wilt in the early stage, middle stage and peak stage of the disease is more than 35%, and the effect in the end stage of the disease is slightly reduced, but still reaches more than 15%, which reflects that intercropping can control faba bean wilt very well . At the same time, the results also reflected that intercropping had the same effect on the disease index of faba bean wilt and the pathogenic bacteria of faba bean wilt, indicating that intercropping inhibited the proliferation of pathogenic bacteria of faba bean wilt in the rhizosphere is one of the important mechanisms for intercropping to control fusarium wilt.

3) Determination of sugars, amino acids and organic acids in root exudates

Put 30 g of rhizosphere soil obtained from the field into 200 mL of extract solution (pH 5.6, including 200 μmol L ^-1 MgCl ₂ , 100 μmol L ^-1 KCl, 600 μmol L ^-1 CaCl ₂ and 5 μmol L ^-1 H ₃ BO ₃ ) container for 1h, during which several times of shaking. After standing still, take about 20mL of the supernatant and put it into a 50mL centrifuge tube, and immediately add 2 to 3 drops of microbial inhibitors (concentrated phosphoric acid with a concentration of 98%, which can inhibit microbial activity and eliminate organic components in the microbial decomposition solution) , concentrated to dry powder with a freeze dryer. Dilute to 1 mL with water before determination, pass through a 0.45 μm membrane, and analyze and determine the content of phenolic acid by high performance liquid chromatography (Agilent 1260 Infinity). Vanillic acid, p-hydroxybenzoic acid, syringic acid, salicylic acid, ferulic acid, benzoic acid and cinnamic acid (chromatographically pure) were used as standard substances. The detection conditions of high performance liquid chromatography are chromatographic column: Kinetex column, 2.6 μm, 4.6×100 mm, column temperature 30°C. Injection volume 10 μL, 280nm DAD detector, flow rate 0.5mL·min ^-1 , mobile phase: A=methanol (chromatographic grade), B=0.1% phosphoric acid-water, separation condition: mobile phase B 80% (0min)→5 %(15.0min)→5%(18.0min)→80%(18.5min)→0%(20.0min)→stop (25.0min) for gradient elution. The types of phenolic acids were determined according to the retention time, and the content of each phenolic acid was calculated by the external standard method.

It can be seen from Figure 2 that after the inoculation of broad bean pathogenic bacteria, the total amount of organic acids in the root system of single intercropping broad bean decreased to varying degrees. On the 1st and 2nd day after inoculation, the total organic acids in intercropped broad bean roots decreased to 84.1% and 51.7% of those before inoculation, and the total organic acids in intercropped broad bean roots decreased to the lowest on the second day after inoculation. On the 3rd day after inoculation, the total amount of organic acids in the roots tended to increase. After being inoculated with the pathogen of faba bean wilt, the organic acids in the root system of faba bean in monoculture also tended to decrease, but the decline rate was not as obvious as that in the intercropping condition.

4) Effects of root exudates on spore germination, hyphal growth and sporulation of Fusarium wilt pathogen

2. The effect of phenolic acid on the mycelial growth of Fusarium wilt

Using exogenous additions of benzoic acid, cinnamic acid, salicylic acid and p-hydroxybenzoic acid, which are high in the root exudates of broad bean and have large differences among single intercropping treatments, the effect of four kinds of phenolic acids on the mycelia growth of the pathogenic fungus Fusarium wilt of broad bean was compared Allelopathy (Table 2).

Compared with the control, the concentrations of benzoic acid 12.5, 25, 50, 100, 200, 400 and 800 mg·L ^-1 significantly reduced the colony diameter by 7.42%, 9.17%, 12.66%, 17.03%, 21.40%, 33.58% and 35.81% , while the treatment concentration was 3.125 and 6.25 mg·L ^-1 , compared with the control, mycelial growth had no significant effect.

Compared with the control, cinnamic acid 50, 100, 200, 400 and 800mg·L ^-1 concentration treatment significantly reduced the colony diameter by 3.93%, 17.90%, 20.96%, 31.44% and 37.55%, respectively, while the treatment concentration was 3.125, 6.25mg ·L ^-1 significantly promoted mycelial growth.

Compared with the control, salicylic acid 50, 100, 200, 400 and 800 mg·L ^-1 concentration treatment significantly reduced the colony diameter by 5.68%, 10.92%, 26.20%, 42.79% and 52.40%, respectively, while the treatment concentration was 3.125, 6.25 , 12.5 and 25 mg·L ^-1 , compared with the control, the colony diameter increased but there was no significant difference.

Low concentrations of benzoic acid, cinnamic acid and salicylic acid can promote the mycelia growth of the pathogenic fungus of Fusarium wilt of broad bean, and show an inhibitory effect with the increase of treatment concentration, showing the allelopathic characteristics of "low promotion and high suppression", and the allelopathic intensity The expression is salicylic acid > cinnamic acid > benzoic acid.

Table 2 Effects of different phenolic acid treatments on the mycelial growth of the pathogenic fungus of broad bean wilt

Different letters in the same column indicate significant difference (P<0.05).

3. Effect of phenolic acid on spore germination of Fusarium wilt

Exogenous addition of phenolic acid had a significant allelopathic effect on FOF spore germination. Compared with the control, all concentrations of salicylic acid showed significant inhibitory effect, and the inhibitory effect was enhanced with the increase of the concentration of treatment; Spore germination; p-hydroxybenzoic acid treatment showed a trend of low concentration inhibition and high concentration promotion, and medium and high concentration treatment significantly promoted FOF spore germination (Figure 3). It indicated that the three phenolic acid treatments had different allelopathic effects on FOF spore germination.

The present invention studies the interaction of root exudates-soil microorganisms-pathogens in the wheat and broad bean intercropping system and its interaction with crop disease resistance, starting from the soil culture of wheat and broad bean intercropping and broad bean monoculture and the inoculation of pathogenic bacteria Collection and detection of rhizosphere soil and root exudates and disease investigation; it was found that the intercropping of wheat and broad bean significantly improved the activity and diversity of microorganisms in the rhizosphere of broad bean, reduced the content of phenolic acids in the rhizosphere soil of broad bean, and reduced the wilt of broad bean in soil The amount of pathogenic bacteria reduces the degree of harm of Fusarium wilt; the research method of wheat and broad bean intercropping of the present invention inhibiting broad bean Fusarium wilt effectively proves this point of view; it is clear that the intercropping system root interaction changes the rhizosphere microbial activity and diversity. The degradation of phenolic acids in the rhizosphere soil reveals that intercropping alleviates faba bean continuous cropping obstacles and is closely related to the interaction between rhizosphere microorganisms, phenolic substances and pathogenic bacteria; and the results help to explain the mechanism of intercropping to control soil-borne diseases, and have great impact on the use of intercropping. It has important guiding significance and application value to improve crop productivity, enhance farmland biodiversity and farmland ecological stability, achieve high grain yield and environmental friendliness, reduce the negative impact of chemical fertilizers and pesticides on the environment, and promote farmers' increase in production and income and sustainable agricultural development. .

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (7)

1. a kind of assay method that wheat broad bean intercropping suppresses broad bean wilt, it is characterized in that, the assay method that described wheat broad bean intercropping suppresses broad bean wilt comprises: the soil cultivation of wheat broad bean intercropping and broad bean single cropping and the inoculation of pathogenic bacteria; Collection of soil and root exudates and disease investigation; determination of sugars, amino acids and organic acids in root exudates; effects of root exudates on spore germination, mycelial growth and sporulation of Fusarium wilt pathogen. 2. the assay method that wheat broad bean intercropping suppresses broad bean wilt as claimed in claim 1, is characterized in that, described step one specifically comprises: basin body size is 14 * 20cm, and every pot dresses soil 2.5kg; Wheat broad bean planting density : 4 broad bean seedlings per pot for single-cropping broad beans, 2 broad bean seedlings for wheat and broad bean intercropping, 4 wheat seedlings, inoculated with faba bean wilt pathogen at the five-leaf stage of broad beans, no pesticides, fungicides and insecticides are used for seedling management . 3. the assay method that wheat broad bean intercropping suppresses broad bean wilt as claimed in claim 1, is characterized in that, described step 2 specifically comprises: Collection method of rhizosphere soil extract solution: use soil shaking method to remove non-rhizosphere soil, extract rhizosphere soil solution with 100ml distilled water, centrifugally filter, filter the filtrate through a 0.45 μm filter membrane, and store it frozen at -20C for later use; Root exudates: Take the roots of broad bean monocropping and wheat broad bean intercropping respectively, wash the roots repeatedly with tap water, and then wash them with distilled water 5 times, soak them in 5 mg/L thymol for 3 minutes, and put them in 0.005mol.L ^-1 CaCl ₂ solution The root exudates were collected by ventilation for 2 hours, and the collected solution was evaporated to dryness in a small rotary at 40 degrees Celsius to 10 ml for later use. 4. the assay method that wheat broad bean intercropping suppresses broad bean wilt as claimed in claim 1, is characterized in that, in described step 2, disease investigation, record grading standard, incidence rate and disease index; The degree of disease is divided into 5 grades: Grade 0: no lesion at the base of the stem and roots, and apparently asymptomatic; Grade 1: slight lesion or discoloration at the base of the stem or root; grade 2: disease at the base of the stem or the main lateral root Spots, but not contiguous: Grade 3: Lesions, discoloration or rot appear on 1/3-1/2 of the base of the stem or root, and the lateral roots are significantly reduced; Grade 4: The base of the stem is surrounded by lesions or most of the roots are discolored and rotten; Grade 5: The plant withers and dies. 5. the assay method that wheat broad bean intercropping suppresses broad bean wilt as claimed in claim 1, is characterized in that, the incidence rate=(pathogenic strain number/investigation strain total number) * 100 of described step 2; Disease index = ∑ (number of diseased plants at all levels × corresponding level value) / (highest level value × total number of investigated plants) × 100. 6. the assay method that wheat broad bean intercropping suppresses broad bean wilt as claimed in claim 1 is characterized in that, the mensuration of sugar, amino acid and organic acid in the root system secretion of described step three, during mensuration, takes out centrifuge tube and thaws from refrigerator , through the membrane; the determination of total sugar content was carried out by anthrone colorimetric method, the amino acid analysis was determined by amino acid automatic analyzer; the organic acid components and content of root exudates were measured by high performance liquid chromatography, and the condition was 250mm×4.6mm C18 Phase column, mobile phase 25mmol.L ^{- 1} KH ₂ PO ₄ , flow rate 1mL.min ^-1 , temperature 31°C, measurement wavelength 214nm, injection volume 20μL. 7. a wheat broad bean intercropping planting method suppressing the assay method of broad bean wilt by the wheat broad bean intercropping described in any one of claims 1～6, it is characterized in that, described wheat broad bean intercropping planting method is on the same big field, moisture Plant 7-10 rows of wheat on the surface, plant 2-4 rows of broad beans on the side, the row spacing between broad beans and wheat is 10-30cm, and broad beans are sown earlier than wheat.