CN107821408B - Application of 6-azauracil in preparing bactericide for preventing and treating plant diseases caused by plant pathogenic bacteria - Google Patents

Abstract

The invention discloses application of 6-azauracil in preparing a bactericide for preventing and treating plant diseases caused by plant pathogenic bacteria. 6-azauracil as bactericide has the advantages of high efficiency and low toxicity, and is suitable for chemical prevention and control of plant diseases. At present, the use of a large amount of bactericides leads to the enhancement of the drug resistance of pathogenic bacteria, and the traditional bactericides have large environmental pollution and high residue and directly threaten the food safety of human beings. The 6-azauracil is a degradable, pollution-free and environment-friendly micromolecule compound, has poor drug resistance, is safe to non-target organisms, people and livestock, can ensure high quality of agricultural products, fruits and vegetables, meets the requirement of sustainable development, and has wide research and market application prospects.

Description

Application of 6-azauracil in preparing bactericide for preventing and treating plant diseases caused by plant pathogenic bacteria

Technical Field

The invention belongs to the technical field of bactericidal active compounds, and particularly relates to application of 6-azauracil in preparation of a bactericide for preventing and treating plant diseases caused by plant pathogenic bacteria.

Background

Plant pathogenic bacteria can cause great harm to the growth and development of plants, and cause great loss to agricultural production every year. Plant diseases are one of natural disasters seriously damaging agricultural production, and according to the estimation of grain and agriculture organizations of the United nations, the annual loss of grain and cotton production all over the world is more than 10 percent due to the diseases. Plant diseases not only cause a reduction in crop yield, but also seriously threaten the quality safety of agricultural products and international trade thereof to some extent.

The history of chemical control of plant diseases has developed with the occurrence of plant diseases, and the practice and application of chemical control has been in history for over a century so far. Human beings gradually summarize experiences in long-term fight against natural disasters and develop a series of bactericides applied to control plant diseases. With the development of times, new products are continuously developed, and more than 300 active ingredients of the bactericide can be used for preventing and treating various plant diseases at present. The prevention and control of plant diseases mainly comprises chemical prevention and control, but due to the long-term use of a large amount of chemical bactericides, the drug resistance of plant pathogenic bacteria is increased year by year, pesticide residues in agricultural products are increased, and great threat is caused to food safety. Along with the progress of human civilization and scientific technology, more efficient, low-toxicity, low-residue and environment-friendly bactericides are required to be developed and applied, and play an important role in agricultural production.

6-azauracil, the name of which is 1,2,4-triazine-3, 5-dione; english name: 5-Amino-1,2, 4-triazine; 6-aza-5, 6-dihydrouracil; 3,5-dioxo-1,2, 4-triazine; 1,2,4-triazine-3, 5-dione; 5-Amino-triazin. CAS number: 461-89-2, molecular formula: c₃H₃N₃O₂Molecular weight 113.07, molecular formula:

6-azauracil is a white crystalline powder, density: 1.86g/cm³Melting point: 274- & ltSUB & gt 275 ℃ (lit.), boiling point: 503.4 ℃ at760mmHg, flash point: 258.3 ℃. The medicine stimulates eyes, respiratory system and skin.

6-azauracil is involved in enzyme inhibitors in purine and pyrimidine biosynthesis and can result in changes in the levels of nucleotide pools in vivo to the extent that transcriptional elongation becomes slower with decreasing nucleotide levels. 6-azauracil has been widely used to study transcriptional regulation, particularly in model microbial yeasts. 6-azauracil has antiviral activity and can be used as an antitumor agent.

At present, application research of 6-azauracil in the aspect of pesticides, particularly as a bactericidal active substance, is not reported at home and abroad.

Disclosure of Invention

The invention aims to provide application of 6-azauracil in preparing a bactericide for preventing and treating plant diseases caused by phytopathogens. Toxicity measurement proves that the 6-azauracil has good inhibitory activity on plant pathogenic fungi and oomycetes. 6-azauracil as bactericide has high efficiency and low toxicity, and is suitable for preventing and treating plant diseases.

In order to realize the purpose of the invention, the invention adopts the following technical scheme to realize:

the invention provides application of 6-azauracil in preparing a bactericide for preventing and treating plant diseases caused by plant pathogenic bacteria.

Further: the plant pathogenic bacteria are fungi of Deuteromycotina, Ascomycotina and Phytophthora ovata.

Further: the effective use concentration of the 6-azauracil in the bactericide is 5-10 mM.

Further: the fungi of the subphylum Deuteromycotina include tobacco leaf blight bacteria, tomato wilt bacteria, cotton verticillium wilt bacteria, tomato early blight bacteria, wheat scab bacteria, peanut black spot bacteria, corn curvularia leaf spot bacteria, cucumber corynespora leaf spot bacteria, botrytis cinerea, blueberry phomopsis longipes, potato wilt bacteria, tobacco brown spot bacteria and blueberry branch blight bacteria.

Further: the Ascomycotina fungi include apple anthracnose leaf blight bacteria, apple ring rot bacteria, apple rot bacteria, pear rot bacteria and blueberry branch canker bacteria.

Further: said Phytophthora Oomycetes comprises Phytophthora nicotianae.

Further: when the concentration of 6-azauracil in the bactericide is 10mM, the inhibition rate of 6-azauracil on tomato early blight bacteria, cucumber corynebacterium sporum, blueberry phomopsis longipes, potato wilt bacteria, apple rot bacteria and blueberry branch canker bacteria is up to 99%.

Further: the plant is selected from apple, pear, tomato, blueberry, tobacco, cucumber, corn, wheat, cotton, grape, potato and peanut.

Compared with the prior art, the invention has the advantages and the technical effects that: at present, the variety of the bactericide has a single action mechanism, and pathogenic bacteria have high propagation speed, so that the bactericide has high resistance, large pollution and high residue, and threatens the food safety of human beings. Indoor toxicity measurement proves that the 6-azauracil has good inhibitory activity on plant pathogenic fungi and oomycetes. 6-azauracil as bactericide has the advantages of high efficiency and low toxicity, and is suitable for chemical prevention and control of plant diseases. At present, the use of a large amount of bactericides leads to the enhancement of the drug resistance of pathogenic bacteria, and the traditional bactericides have large environmental pollution and high residue and directly threaten the food safety of human beings. The 6-azauracil is a degradable, pollution-free and environment-friendly micromolecule compound, has poor drug resistance, is safe to non-target organisms, people and livestock, can ensure high quality of agricultural products, fruits and vegetables, meets the requirement of sustainable development, and has wide research and market application prospects.

Drawings

FIG. 1 shows the results of the bacteriostatic test of 6-azauracil against tobacco leaf blight bacteria in the present invention;

FIG. 2 shows the results of experiments on the inhibition of 6-azauracil against Fusarium oxysporum of tomato in the present invention;

FIG. 3 shows the results of experiments on the inhibition of 6-azauracil against verticillium dahliae of cotton;

FIG. 4 shows the results of the experiments on the inhibition of 6-azauracil against early blight of tomato in the present invention;

FIG. 5 shows the results of experiments on 6-azauracil-derived bacteria of Gibberella zeae;

FIG. 6 shows the results of experiments on the inhibition of peanut alternaria by 6-azauracil;

FIG. 7 shows the results of the bacteriostatic test of 6-azauracil against Curvularia zeae;

FIG. 8 shows the results of the bacteriostatic test of 6-azauracil against Pseudocercospora cubensis according to the present invention;

FIG. 9 shows the results of experiments on the inhibition of Botrytis cinerea by 6-azauracil according to the present invention;

FIG. 10 shows the results of experiments on the inhibition of Sclerotinia solanacearum by 6-azauracil in blueberry;

FIG. 11 shows the results of experiments on the inhibition of 6-azauracil against potato wilt bacteria in accordance with the present invention;

FIG. 12 shows the results of the bacteriostatic test of 6-azauracil against Alternaria alternata according to the present invention;

FIG. 13 shows the results of experiments on the inhibition of Sclerotinia solanacearum by 6-azauracil.

FIG. 14 shows the results of the experiments on the inhibition of Bacillus anthracis by 6-azauracil according to the present invention;

FIG. 15 shows the results of experiments on 6-azauracil inhibition of apple ring spot;

FIG. 16 shows the results of the experiments on the inhibition of apple rot by 6-azauracil according to the present invention;

FIG. 17 shows the results of the experiments on the inhibition of Pyricularia oryzae by 6-azauracil in accordance with the present invention;

FIG. 18 shows the results of the bacteriostatic test of 6-azauracil on branch and trunk ulcer germs of blueberry in the present invention;

FIG. 19 shows the results of the bacteriostatic test of 6-azauracil against tobacco phytophthora parasitica according to the present invention.

Detailed Description

The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

Example 1

First, experimental material

The 6-azauracil reagent was a finished product purchased from Sigma. Weighing 6-azauracil according to the specific requirements of the experiment, dissolving in dimethyl sulfoxide to prepare a mother solution with the concentration of 100mM/L, filtering, sterilizing and storing at 4 ℃ for later use.

The plant pathogenic bacteria used in the experiment are strains stored at 4 ℃ in a laboratory, and the adopted culture medium is a potato culture medium (PDA for short).

The PDA culture medium formula comprises: potato (peeled) 200g, glucose 20g, agar 15g, tap water 1000ml, natural pH.

The preparation method comprises the following steps: cleaning and peeling potato, weighing 200g, cutting into small pieces, adding water, boiling (boiling for 20-30 min, and being broken by a glass rod), filtering in a beaker by eight layers of gauze, adding 15-20g of agar according to experiment requirements, adding 20g of glucose, stirring uniformly, slightly cooling to supplement water to 1000ml after full dissolution, subpackaging, sterilizing at 121 ℃ for 20 min, and cooling for later use.

Second, Experimental methods

A growth rate method is used.

1. Firstly culturing 19 plant pathogenic bacteria on a PDA plate at 25 ℃ for about 2 days for later use.

2. Heating PDA culture medium to melt, cooling to 45-50 deg.C, adding 6-azauracil to obtain culture medium containing 2.5, 5, and 10mM medicinal liquid (adding dimethyl sulfoxide of corresponding volume to control), and cooling in culture dish.

3. Taking out the proper activated phytopathogen from the incubator, aseptically beating a circular cake (with diameter of 0.60cm) on the edge of each strain hypha (with growth condition as consistent as possible) of the 2d culture, picking up the cake to the center of the drug-containing plate by using an inoculating needle, and then placing the culture dish in the incubator (25 ℃) for culture.

4. Observing and measuring the growth condition of hyphae at different time after treatment, measuring the diameter by adopting a cross method, processing data, calculating the inhibition rate and taking a picture.

Inhibition (%) (control hypha diameter-treated hypha diameter)/control hypha diameter × 100;

each treatment was repeated 3 times.

Bacteriostatic effect of tri-and 6-azauracil on growth of 19 plant pathogenic bacteria hypha

1. Tobacco leaf blight bacteria: the tobacco target leaf spot is mainly caused, is a leaf disease, is easy to perforate after a disease spot is cracked after the disease spot is infected on a leaf, and is finally necrotic when the disease spot is severe. The disease is characterized by high epidemic speed, and causes serious harm to the quality of tobacco. Besides tobacco, the pathogen can also infect grain crops such as sorghum, corn, cotton, wheat, barley, rice, soybean and the like, plants such as beet, black nightshade, eggplant, kenaf, tomato, petunia and the like under natural conditions, and the host range is wide and can reach more than 200 plants.

2. Tomato fusarium wilt bacteria: it mainly causes tomato wilt, also called wilting disease. The pathogen mainly infects conduit tissues of plants during infection, so that the water and substance in xylem are blocked to cause plant wilting. Different from other plant pathogenic bacteria which have a plurality of hosts, the pathogenic bacteria only carry out infection harm on tomatoes and have strong specificity. Meanwhile, the germs are mainly spread by soil, and can be infected from the seedling stage to the adult stage of the tomatoes, so that the yield and the quality of the vegetables are seriously influenced, and particularly the germs are seriously spread in a greenhouse of old vegetables.

3. Cotton verticillium wilt: the verticillium wilt of cotton is mainly caused, host plants can be caused to generate the verticillium wilt, and the current various prevention and control means such as biological prevention and control, chemical prevention and control, conventional genetic breeding and the like have no way of timely and effective prevention and control, so that serious economic loss is caused in China and all over the world. The host range of the pathogenic bacteria is very wide, 660 plants including 184 crops and 153 weeds can be infected according to related reports of foreign media, and 38 plants are used in total. Within our country, host plants have been identified in about 80, 20 families, including various field crops such as kidney bean, cotton, cucumber, eggplant, sunflower, tomato, pepper, sesame, potato, melon, watermelon, peanut, mung bean, beet, etc.

4. Tomato early blight: the main reason for the occurrence of the disease is that most areas begin to popularize the tomato variety for resisting virus infection, so that the prevention and treatment of the early blight are reduced, and the disease is seriously damaged. The pathogenic bacteria can cause diseases in the seedling stage and the adult stage of plants. When the seedlings are attacked in the seedling stage, the base of the stem of the seedling in the affected area generates ring lines, and dark brown spots and pits occur. In the adult stage, the disease spots generally develop from the lower leaves to the upper leaves. The pathogen has various parasitic plants, including Solanaceae vegetables such as tomato, eggplant, pepper and potato.

5. Wheat scab: is extremely destructive, generally resulting in ear rot, reduced crop quality and severe yield loss. The host range of the pathogen is very wide, and the pathogen comprises gramineous weeds such as barley, oat, rice, corn, goose corolla and the like, soybeans, cotton, sweet potatoes and the like. The spread of wheat scab has been particularly widespread in recent years, mainly due to changes in farming systems and farming styles, and global warming. The disease can cause the infected wheat grains to contain fungal viruses, which can cause human and animal poisoning and fungal diseases through transmission, and can also cause the quality reduction and yield reduction of wheat and generate huge economic loss.

6. Peanut alternaria alternata: the phenomenon of premature senility can be mistaken for the symbol of precocity of peanuts, and finally the yield of the peanuts is reduced greatly. The more long the continuous cropping period of the disease occurs, the more serious the disease occurs, the less the disease occurs in the crop rotation land and the more serious the disease occurs in the continuous cropping land, so the reasonable planting needs to be paid attention to in the peanut planting process.

7. Curvularia lunata (L.) Pilat: it mainly causes pseudocercospora, also known as black mold. The different varieties of the pathogen show different symptoms after infection, and the disease mainly damages corn leaves and sometimes also damages leaf sheaths and bracts. Meanwhile, the germs can be parasitic on rice, sorghum, wheat and some lawns, and can infect fruits such as tomatoes, peppers and the like, so that diseases are caused, and the yield and the quality of the fruits are reduced. In recent years, the diseases are mainly applied to the corn producing areas in northeast and north China. The disease is characterized by rapid spread, paroxysmal, difficult control, and when the disease is serious, the leaf part of the plant is densely spotted, and when the disease is serious, the disease leaf rate of the diseased plant almost reaches full coverage, thus seriously affecting the development of the corn producing area in China.

8. Cucumber corynespora leaf spot: the cucumber corynespora leaf spot is mainly caused, is an important plant pathogenic fungus and is firstly found on vegetables such as cucumbers, cowpeas and the like. The germs mainly infect leaves of host plants, and simultaneously infect stems, flowers and fruits, and can cause the phenomena of plant leaf falling, fruit falling and the like when the disease is serious. According to the investigation in recent years, the bacterium can infect more than 530 plants, and can cause infectious outbreak on crops such as rubber, and the future development prospect of the agricultural industry is seriously threatened. Once occurred in large areas of up to 11 provinces such as inner Mongolia, Shandong, Liaoning, Hebei and so on in China, the economic loss is very serious.

9. Botrytis cinerea: the botrytis cinerea is mainly caused, is a common disease in grape planting and is one of the most harmful diseases, and meanwhile, the germs belong to facultative parasitic bacteria, can infect various flowers, vegetables and the like, and have a wide host range. The disease is more harmful in grape production in protected areas in the north of China and grape plantation in southern areas, and the development of facility cultivation grape industry in the north of China is greatly restrained. Besides causing damage during planting, the grapes can also be infected by the germs during storage, thereby causing irreparable serious consequences and greatly influencing the yield and quality of the grapes. According to incomplete statistics, the economic loss caused by grape gray mold in China accounts for 20% every year, and can reach 30% in severe cases.

10. The method comprises the following steps of (1) providing blueberry phomopsis shoot: mainly parasitizes in peach, pear, larch, cowberry and other plants, and has wide host range. After the blueberry is infected by the germs, the blueberry branch diseases can be caused, and the quality and the yield of the blueberry are reduced.

11. Potato wilt germs: fungal pathogens, which are mainly transmitted by soil, occur in various planting areas in the world. Can be parasitic on banana, solanaceae, leguminous, melon cotton, flowers and other plants, and can cause blight. After being infected by the bacterium, the plant generally shows weak growth, withered and wilted plant, and browning of vascular bundles, and has various symptoms. The disease is particularly serious in recent years, particularly in potato continuous cropping fields, the quality of agricultural products is seriously influenced, the yield is greatly reduced, and the economic loss is serious.

12. Alternaria alternate: mainly causes alternaria alternate, seriously harms the development of tobacco industry in China, and belongs to fungal diseases. The infected tobacco can cause the incomplete damage of the leaves, the quality and the industrial use value of the tobacco are reduced, and the taste of the tobacco is reduced to a certain extent due to the different components of the tobacco leaves. The germs can also infect tomato, peach, plum, cotton, wheat, soybean and other plants to cause diseases such as root rot, spot disease and the like, and the host range is wide.

13. Blueberry branch blight bacteria: mainly causes blueberry branch blight, is an important plant pathogen, and belongs to Pestalotiopsis. After being infected by the pathogenic bacteria, the main symptoms are ulcer, leaf spot and the like, and according to statistics, the host plants of the pathogenic bacteria have over fifty types. At present, common blueberry main cultivars such as blueberries, duke and the like have branch blight, and have great influence on the yield and quality of fruits. The research on the pestalotiopsis is has great significance for recovering the loss of agricultural and forestry economic crops.

14. Apple anthracnose leaf blight bacteria: the anthracnose and leaf blight of apple is mainly a leaf disease, mainly harms leaves and is caused by anthracnose pathogen. The apple trees infected by the pathogen have weakened tree vigor and a large amount of fallen leaves, and fruits of the apple trees also have severe rot phenomena. The major harmed apple varieties comprise Qianyin, Qinhuan, Gala, golden crown and the like, and a large amount of yield reduction and even dead production can be caused in the next year in severe cases. The contrast between the high disease-resistant Fuji and Hongxing in apple varieties and the Gala and Jinguan varieties with the same disease is very strong if the varieties are in the same orchard.

15. Apple ring rot bacteria: the germs can cause ring rot disease and rough skin disease of the apples, mainly cause diseases of branches and trunks and fruits of the apples and generate important disasters, thereby causing uneven and local necrosis of the barks and rotten apples. The fruit setting rate of plants infected by the pathogen is low, and the corresponding results also cause the reduction of apple yield and the weakening of trees, and sometimes even cause the dead orchard. Due to the heat of Fuji apples, in recent years, the annual incidence rate of ring rot of apples is increased due to the beginning of large-area cultivation of susceptible Fuji apples, the area of an apple planting area damaged by the ring rot of apples is continuously enlarged, and the ring rot of apples has a bad influence on the continuous development of the apple industry and becomes one of main diseases damaging the apple planting.

16. Apple canker, which is the main pathogen causing the apple branch and trunk diseases with the strongest destructiveness to apple trees, forms dead branches and dead trees of the apple trees, and can cause garden damage in severe cases, thereby causing large-area yield reduction and causing huge economic loss. Because host plants of apple tree canker are relatively extensive, common fruit trees such as apples, peaches and pears are parasitic targets.

17. Pear rot germs: the germs mainly cause pear rot, also called as rotten skin disease, and have three main characteristics: wide related area, high disease rate and difficult prevention and control. The method is widely distributed in pear tree planting areas in various places of China, and is particularly seriously harmful in northeast, north China, Xinjiang and other places. The germs mainly infect main branches and side branches of pear trees, can cause pear tree weakness, and can seriously reduce the quality of fruits and influence the yield of pears. The orchard with great harm is full of scabs and trunk defects, and even a great amount of dead trees or garden damage can be caused.

18. Blueberry branch canker pathogen: the host range is wide, and can reach 40 broad-leaved genera and 5 coniferous genera. Especially, the damage to forest and fruit trees is serious, and serious diseases such as tree canker and the like can be caused.

19. Tobacco black shank: the tobacco black shank is mainly caused, all cultivated tobaccos such as flue-cured tobaccos, air-cured tobaccos, sun-cured tobaccos, aromatic tobaccos and burley tobaccos are damaged, and the tobacco black shank is one of main diseases which are destructive to the growth and development of the tobaccos in the global range and is extremely destructive. The disease is particularly serious in rainy years and low-lying humid areas with the average temperature of 22 ℃. The host range under natural conditions is narrow, and only tobacco is infected.

The in vitro bacteriostasis biological test result of the 6-azauracil on 19 plant pathogenic bacteria is shown in the table 1.

TABLE 16 results of inhibition of hypha growth of 19 pathogenic bacteria by azauracil (5d)

Note: three replicates were set for each treatment in the experiment and the data in the table are the average of the three replicates.

As is clear from Table 1, the inhibitory effect on 19 plant pathogenic fungi was successively improved with the increase in the concentration of 6-azauracil. When the concentration of the 6-azauracil is 10mM, the 6-azauracil has a good inhibition effect on 19 plant pathogenic bacteria of Deuteromycotina, Ascomycotina and Oomycotina, wherein the inhibition rate on 16 plant pathogenic bacteria of tomato wilt bacteria, cotton verticillium wilt bacteria, tomato early blight bacteria, peanut black spot bacteria, corn curvularia leaf spot bacteria, botrytis cinerea, blueberry phomopsis longipes, potato wilt bacteria, blueberry branch blight bacteria, apple anthracnose leaf blight bacteria, apple ring rot bacteria, pear rot bacteria, blueberry branch canker bacteria and tobacco black shank bacteria is up to more than 90%. Especially, the bacteriostatic effect on 6 pathogenic bacteria such as tomato early blight bacteria, cucumber corynespora leaf spot bacteria, blueberry phomopsis longipes, potato wilt bacteria, apple rot bacteria and blueberry branch canker bacteria is best, the inhibition rate is more than 99%, and the effective prevention and control can be carried out on the pathogenic bacteria.

As shown in figures 1-19, when the concentration of 6-azauracil is 10mM, 14 pathogenic bacteria such as tomato early blight, apple ring spot, tobacco black shank and the like hardly grow hypha, and 5 plant pathogenic bacteria such as tobacco target spot, tomato fusarium wilt, wheat fusarium wilt, cotton verticillium wilt and tobacco brown spot only grow few hypha, so that 6-azauracil has a good inhibition effect. In conclusion, 6-azauracil has a great potential for application in the control of phytopathogens.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions.

Claims (4)

1. Use of 1, 6-azauracil for the preparation of a fungicide for the control of plant diseases caused by phytopathogens, characterized in that: the plant pathogenic bacteria are fungi of Deuteromycotina, Ascomycotina and Phytophthora ovata;

   the fungi of the subphylum imperfecti are tomato fusarium wilt bacteria, cotton verticillium wilt bacteria, tomato early blight bacteria, wheat fusarium graminearum, peanut alternaria alternata bacteria, corn curvularia leaf spot bacteria, cucumber corynespora leaf spot bacteria, blueberry phomopsis longipes, potato fusarium wilt bacteria, tobacco alternaria alternata and blueberry branch fusarium wilt bacteria; the ascomycotina fungi are ring rot of apple, rot of pear and branch ulcer of blueberry; the phytophthora parasitica of phylum Oomycetes is tobacco black shank fungus.
2. 2. Use of 6-azauracil according to claim 1 for producing a fungicide for controlling plant diseases caused by phytopathogens: the effective use concentration of the 6-azauracil in the bactericide is 5-10 mM.
3. 3. Use of 6-azauracil according to claim 1 for producing a fungicide for controlling plant diseases caused by phytopathogens: when the concentration of 6-azauracil in the bactericide is 10mM, the inhibition rate of 6-azauracil on tomato early blight bacteria, cucumber corynebacterium sporum, blueberry phomopsis longipes, potato wilt bacteria, apple rot bacteria and blueberry branch canker bacteria is up to 99%.
4. 4. Use of 6-azauracil according to claim 1 for producing a fungicide for controlling plant diseases caused by phytopathogens: the plant is selected from apple, pear, tomato, blueberry, tobacco, cucumber, corn, wheat, cotton, potato and peanut.

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