Synergistic Control Of Rubber Root Disease And Anthracnose By Bacillus Subtilis Czk1 And Chemical Fungicide

The Brazilian rubber tree（Hevea brasiliensis（Willd.ex A.Juss.）Muell.Arg）is the main specie of natural rubber tree in China.Root disease and anthracnose of rubber tree are extremely serious diseases in the rubber plantation area of China.Till now,the prevention and control measures of the two diseases are mainly based on chemical control,supplemented with agricultural control and biological control.However,chemical control has serious environmental pollution to the soil;agricultural prevention and control is time-consuming and laborious;biological control requires a long time and the field control effect is unstable;these problems have seriously restricted the sustainable development of natural rubber industry of China.The combined control method of bio-control bacteria and chemical fungicides can not only reduce the use of chemical fungicide and its drug resistance and pollution,but also make up the shortages of biological control and agricultural control.In the present study,rubber red root pathogen,rubber brown root pathogen and rubber anthracnose were the target fungi to explore the feasibility of Bacillus subtilis Czk1 and chemical fungicides to control them.Growth fungicide with good compatibility with Czk1.Determine the indoor bacteriostatic effect and pot plant control effect of Bacillus subtilis Czk1 and chemical fungicide compound on the pathogens.The fungus-drug compound composed of fungicides is intended to provide a theoretical basis for the sustainable control of the diseases.The main research contents and results are as follows:（1）To determine the virulence effect of 7 chemical bactericides on rubber red root pathogen Gp030 and rubber brown root pathogen Pn006 by bacteriostatic circle method and cross method,Its EC₅₀values were 0.6253 ug/m L and 0.0522 ug/m L,respectively;the toxicity of 7 chemical fungicides against anthracnose rubber RC178 was determined.The results showed that prochloraz had the best antibacterial effect on RC178,and its EC₅₀value 0.0778 ug/m L,followed by Genkang,EC₅₀value was 0.4733 ug/m L.The effects of10 chemical fungicides on the colony formation and spore germination of Bacillus subtilis Czk1 were determined by the dilution coating method and the colony counting method respectively.Among them,Genkang is very compatible,no matter the high concentration or low concentration has little effect on its growth,and even found that high concentration will also promote the growth of bacterial colonies.Prochloraz has good compatibility with Czk1,but only has a slight inhibitory effect at high concentration.（2）The virulence effect of Bacillus subtilis Czk1 on rubber tree root disease and anthracnose pathogens was determined by the flat-faced filter paper method.The results showed that the bacterial colony number of Bacillus subtilis Czk1 against rubber red root pathogen Gp030 was 6.46×10⁷cfu/m L,the number of colonies in the inhibition of rubber brown root pathogen Pn006 was 2.33×10⁸cfu/m L;the number of colonies in the inhibition of Czk1 on the anthracnose RC178 of rubber tree was 4.75×10⁷cfu/m L.（3）The Horsfall method is used to determine the compounding plan of the fungus and medicine,using a concentration of 0.6253ug/m L Genkang and a concentration of6.46×10⁷cfu/m L bio-control bacteria Czk1,when V（Czk1）:V（Genkang）=7:3.the synergistic ratio of red root pathogen Gp030 is 1.60,with the best synergistic effect;it is mixed with the concentration of 0.0522 ug/m L Genkang and the concentration of2.33×10⁸cfu/m LCzk1,when V（Czk1）:When V（Genkang）=7:3,the synergistic ratio IR value of brown root pathogen Pn006 is 1.51,and the synergistic effect is the best.Mix the concentration of 0.4733ug/m L Genkang and 0.0778ug/m L prochloraz with the concentration of 4.75×10⁷cfu/m L bio-control bacteria Czk1,when V（Czk1）:V（Genkang）=7:3.The strongest synergistic effect on the rubber anthracnose RC178 inhibition,the synergistic ratio IR value is 1.36,the best synergistic effect;when V（Czk1）:V（prochloraz）=8:2,the inhibition of RC178 The synergistic effect is the best and the synergistic ratio IR value is 1.65.（4）According to different application intervals of rubber tree root disease and rubber tree anthracnose,continuous indoor virulence and bacteriostasis changes were observed,Three months later,Genkang bacteriostatic rate of rubber red root pathogen Gp030 and rubber brown root pathogen Pn006 decreased significantly.The highest concentration of Genkang Gp030 decreased from 78.75%of the original bacteriostatic rate to 31.76%Pn006 decreased from 91.76%of the original bacteriostatic rate to 0,while the compound of Genkang and Czk1 did not decrease the bacteriostatic rate of Gp030,but the optimal ratio of bacteriostatic rate increased from 76.66%of the original bacteriostatic rate To91.95%,Pn006 changed from 89.32%of the original bacteriostatic rate to 88.78%,which was basically consistent with the original（three months ago）.A month later,Genkang and prochloraz decreased the rubber anthracnose RC178 from 49.41%and 73.73%of the original bacteriostatic rate to 36.32%and 41.10%,respectively,while the compound of Genkang and Czk1 against RC178 From the original 88.32%to 90.00%,the antibacterial rate of the compound of prochloraz and Czk1 on RC178 changed from the original 81.15%to 90.00%,and the antibacterial rate increased.（5）The RC178 spore suspension with a concentration of 1.0×10⁶cfu/m L was sprayed by acupuncture to conduct in vitro leaf and pot planting inoculation experiments.The overall control effect of isolated leaf showed that the prevention effect was better than the treatment effect,and the disease index was lower.Among all the experimental groups,the high concentration of prochloraz has the best control effect,with a control effect of 75.00%;the high concentration of prochloraz,Genkang,and Czk1 compound agents have good control effects on detached leaves.The control effects are:88.89%and 83.33%;but only a single Czk1 biological control effect is not good,the high concentration control effect is63.89%,the low concentration control effect is only 27.78%;potted plant control effect statistics,two months after application of prochloraz The control effect of 500 times solution is still the best,the control effect is 91.67%,but the phytotoxicity is serious,the leaves shrink,the color becomes dark green,whitening,and cannot grow normally;the high concentration of prochloraz and Czk1 compound also has The control effect was77.78%for minor diseases.The medium concentration of prochloraz and Czk1 compound and the high concentration of Genkang and Czk1 compound were better,75.00%and69.44%,respectively,and there was no phytotoxicity.Three different concentrations of Genkang,Czk1 fermentation broth,and fungus medicine compounding agents were high,medium,and low.After one month of application,inoculation with brown root fungus.After three months,the incidence and control effect were counted.The results showed that a single dose Genkang’s high-concentration 100-fold solution has the lowest disease index,the best control effect,and the control effect is 45.16%;Genkang and Czk1 compound high-concentration disease index is also low,the control effect is relatively good,and the control effect is 38.17%.（6）Comprehensive indoor bacteriostasis effect,continuous effect of medicinal effect,potted plant prevention effect,dosage and phytotoxicity,it is recommended to use high concentration of Genkang and Czk1 mixed solution at intervals of about 3 months for rubber tree root disease In the follow-up field application program,the medium concentration of the mixed solution of prochloraz and Czk1,and the high concentration and medium concentration of the mixed solution of Genkang and Czk1,at intervals of about 1 month,were used as the follow-up field application program for anthracnose of rubber trees.