The Biocontrol Effect of Trichoderma and Bacillus Subtilis SY 1

As years of unreasonable farming practices in agriculture soil damaged seriously. The soil-borne disease and the chemical residue are two serious problems of soil pollution which affect the yield and quality of agricultural products. Ecological remediation of soil is an effective way to resolve these problems. In this paper, the agents’ trichoderm and the Bacillus subtilis SY1 were used to improve the ecosystem function and reduce the disease occurrence.


Introduction
The sensitivity of Ginseng to pathogenic fungus has increased after being domesticated out of wildness state.It is reported that there are more than thirty kinds of diseases harmful to Ginseng's growth statistically which can aggrieve its roots, flowers, fruits and could result in fall of production, quality of seeds and roots (Charron.D., Gagnon. D., 1991;W. G. Bailey. 1996,).
Except for the chinese herbal medicine, the problem of plant fungal pathogens are common in agriculture nowadays, especially in facility agriculture.As a new direction for biological control method has recently been developed and beneficial agents, such as Bacillus subtilis (Shinji Mizumoto et al, 2007;Wang J et al, 2007;Marc Ongena et al, 2005) are widely used.
In this paper, trichoderm and Bacillus subtilis SY 1 were used in the experiments to determine their biocontrol effect to pathogen fungi in soil.trichoderm a could antagonize several typical pathogen fungi of American ginseng and decrease the disease occurrence.The eggplant planting experiments indicated that Bacillus subtilis SY1 not only could antagonize several pathogen fungi of eggplant but could promote the seedling growth and increase its stress tolerance.

Microbial agents
The Bacillus subtilis SY1 used through this work was preserved in the laboratory.
Nine pathogenic fungi of American Ginseng and one anti-biotic fungus Trichoderma were separated in the Ginseng planting base.
The four vegetable plant pathogens are provided by Vegetable Research Institute, Tianjin Academy of Agriculture Sciences.

Experimental method
2.2.1 American ginseng experiment 2.2.1.1The confrontation experiment In the confrontation experiment, on the PDA media a piece of 5 mm diameter antagonistic fungi (3 days old cultures) was put on one side and the pathogen fungi (7 days old cultures) of the same size was put on the other side, 4cm apart from each other.In the control experiment 5mm diameter pathogen fungi were put on the PDA media.All the experiments were repeated 5 times The plates were incubated at 28±1 for 7 days to detect the antibacterial effect.
(1) I-Antibacterial effect; R1-Straight-line distance between the center of the pathogen fungi and the edge of antagonistic fungi; R2-The radius of the control pathogen fungi.

American ginseng field experiment
The field experiment of inoculated and control were undertaken in the American ginseng planting base.The inoculated and the control were undertaken simultaneously and were both repeated three times.After disinfecting, the ginseng roots were regularly arranged on the land which surface soil was removed in advance.After covering the soil back onto ginsengs, 5 mL trichoderm suspension was added as liquid to the roots of the American ginseng.Three times of inoculation were did in the first three month after sowing.The desease occurrence were determined after 12 month.

Antagonistic examination
In vitro antagonistic examination of the antifungal activity of Bacillus subtilis SY1 was tested against the four typical soil-borne pathogen diseases on the PDA media.Spore suspensions with different fungi (5 days old cultures, the concentration was more than 106 cfu / mL) have been prepared in 0.85% sterilized saline.The melted solid wateragar medium was put on the plates, the sterile stainless steel columns were put on the frozen solid agar.When the melted semisolid PDA media cooled to 40-50 , 1 mL of spore suspensions of each fungus was put in and well -mixed with PDA media.The mixture was then put onto the wateragar medium plates using transfer pipet.When the agar was frozen solid, the stainless steel columns were taken away and 50 ȝL transformation was put into the hole except the controls (put into 50 ȝL sterilized saline).Every treatment was repeated three times.The plates have been incubated at 28±1 for 7 days to detect the diameter of fungal inhibition around.

Eggplant seedling growth promoting examination
Eggplant seeds were disinfected with 70% ethanol -water ratio solution and then with 0.5% sodium hypochlorite.After rinsing six times with sterile water, the seeds were soaked in the water to pregermination.After three days, eggplant seeds were selected and sown into the pots.The plants were irrigated with water every other day.After 20 days, the growth situation and antioxygen enzyme of eggplant seedling were determined.The American ginsengs in each block were dug out to be detected one years later, and the root diseases were classified according to its condition.Table 2 shows the ginseng root diseases rate.Disease rate %=100-Grade 0 ginseng number /total ginseng number×100 (2)

The antagonistic examination
In vitro antagonistic examination of the antifungal activity of Bacillus subtilis SY1 was tested against the four typical soil-borne pathogen diseases on the PDA media.Spore suspensions with different fungi (5 days old cultures, the concentration was more than 106 cfu / mL) have been prepared in 0.85% sterilized saline.The melted solid wateragar medium was put on the plates, the sterile stainless steel columns were put on the frozen solid agar.When the melted semisolid PDA media cooled to 40-50 , 1 mL of spore suspensions of each fungus was put in and well -mixed with PDA media.The mixture was then put onto the wateragar medium plates using transfer pipet.When the agar was frozen solid, the stainless steel columns were taken away and 50 ȝL transformation was put into the hole except the controls (put into 50 ȝL sterilized saline).Every treatment was repeated three times.The plates were incubated at 28±1 for 7 days to detect the diameter of fungal inhibition around.
From Table 3 and Fig 1 we can see that Bacillus subtilis SY1 has antifungal activity to all these four pathogens to a certain extent, especially D Alternaria solani the diameter of fungal inhibition ring attained 43.6 mm.Alternaria solani is the most common and harmful soil-borne pathogen fungi in agriculture which causes decline of plant yield and quality every year.Bioremediation of inoculating beneficial bacteria Bacillus subtilis SY1 is an effective method to decrease the pathogen fungi amount.The lower quantity and activity of soil-borne pathogen fungi could decrease the disease occurrence so as to guarantee a bumper harvest.

Eggplant field experiment
The eggplants growth condition were determined after 3 months, and the diseases condition were classified.Table 2 shows the eggplants diseases rate.

The growth situation and antioxygen enzyme of eggplant seedling
After 20 days' growth, eggplantseedlings selected in random order were dug out and cleaned with sterile water and plant height, dry weight, chlorophyll content, antioxidant enzyme such as SOD, CAT and POD were determined.The results are shown in Table 2.
From Table 2 we can clearly see that the growth of seedling and the antioxidant enzyme activities in the plant all improved after inoculating the Bacillus subtilis SY1.The Plant height and the dry weight of the seedling increased 56.61 % and 33.55 % respectively.The improvement of chlorophyll content and antioxidant enzyme activities stands for the increase of plant metabolism and stress tolerance.The chlorophyll content is closely related with photosynthesis which provide energy to the plant.SOD is a common enzyme that exists throughout the animal and plant kingdoms, it could remove the superoxide radical.The activity of CAT has a great impact on plant resistance to cold and disease.POD is a highly active enzyme that also common exists in the plant which is closely related to the respiration, photosynthesis and degradation reaction of growth hormone.

Conclusions
In the American ginseng planting experiment the biocontrol aggent trichoderm has great antifungal effect to several pathogens that common in American Ginseng planting soil.After inoculating the trichoderm, the disease occurrence deased significantly.
In the eggplant planting experiment the Bacillus subtilis SY1 has great antifungal effect on pathogens and the growth and stress resistance of the seedlings in the inoculated soil increased.After inoculating, the plant height, dry weight and chlorophyll content increased by 56.61%, 33.55% and 40.1% respectively.The antioxidant enzymes SOD, CAT and POD improved significantly by 103.2 %, 127.3% and 81.5 %.
Chlorophyll content--By means of ethanol extraction Superoxide dismutase (SOD)--By means of nitroblue tetrazolium photoreduction Catalase (CAT) --By means of ultraviolet absorption Peroxidase (POD) --By means of guaiacol method (Wu et al, 2006) 3. Results and discussion 3.1 American ginseng experiment 3.1.1The confrontation experiment 3.1.2American ginseng field experiment small disease spots on the ginseng root surface Grade 2: disease spots on 1/5 of the surface Grade 3: disease spots on 1/5 of the surface Grade 4: 1/2 of the root rot Grade 5: most of the root rot few small disease spots on the leaves and the stems anosis Grade 2: disease spots on most of the leaves and the stems anosis Grade 3: most of the leaves turn yellow but the stems anosis Grade 4: most of the leaves turn yellow and the stems rot Grade 5: withered plant disease index %=(disease plant numbers of each grade×grade number)/(total plant numbers×9)×100 (3)

Table 1 .
Antibacterial effect of trichodermto American ginseng fungous diseases

Table 3 .
Inhibitory activities of Bacillus subtilis SY1 to four typical pathogens

Table 5 .
The growth situation and antioxidant enzyme activities of eggplant seedling after 20 days