| Potato black scurf is a soil-borne fungal disease caused by Rhizoctonia solani.At present,chemical agents such as azoxystrobin and thifuroamide are mainly used to control the disease,but fungicide residues can lead to environmental pollution and other problems.Biological control has become a research focuse because of its advantages of being friendly to the environment,low toxicity and low drug resistance.However,the high-effective biocontrol agents are limited.When biocontrol agents are applied in the field,there are still some problems,such as unstable control effect in applicaiton in the field.The combination of biocontrol agents and chemical fungicides can reduce fungicide residues and control plant diseases efficiently.In this study,the chemical agents with good compatibility with Bacillus velezensis HN-Q-8 were selected through laboratory toxicity test.The colonization stability of Bacillus velezensis HN-Q-8 and its promoting effect on potato seedling were studied by pot experiments in greenhouse.Moreover,the control effect of the mixture of control agents and chemical fungicides on Rhizoctonia solani was tested in the field,and the control program of compound agent applied in the field was determined.The main results were as follows:1.The compatibility of Bacillus velezensis HN-Q-8 with thiafuracil-azoxystrobin and ningnanmycin-azoxystrobin was great and three compound proportion with obvious synergism was determined.The results of the compatibility test in laboratory indicated that thiafuracil-azoxystrobin and ningnanmycin-azoxystrobinhad showed relatively good compatibility with Bacillus velezensis HN-Q-8.When the concentration of thiafuracil-azoxystrobin and ningnanmycin-azoxystrobinhad was 10-500 mg/mL,Bacillus velezensis HN-Q-8 could grow normally.The mixture ratio was selected by Horsfall method.When the volume ratio of thiafuracil-azoxystrobin and the HN-Q-8 fermentation liquid was 1:9 and 2:8,and the volume ratio of ningnanmycin-azoxystrobin and the fermentation liquid of HN-Q-8 was 7:3.the synergistic effects of the mixture were mostly obvious.The efficiency enhancement ratio IR value is 1.31,1.13 and 1.12 respectively.2.The colonization of Bacillus velezensis HN-Q-8 mixed with thiafuracil-azoxystrobin and ningnanmycin-azoxystrobin in potato rhizosphere was stable.Through rifampicin resistance screening method,strain HN-Q-8Rif was obtained.The inhibiting effects on R.solani between subculture broth of Bacillus velezensis HN-Q-8Rif and the fermentation broth of Bacillus velezensis HN-Q-8 were no significant difference.The pot experiment showed that strain HN-Q-8Rif in three compounds could be stably colonized in potato rhizosphere.Colonization of Bacillus velezensis HN-Q-8 in potato rhizosphere.3.When the volume ratio of ningnanmycin-azoxystrobin and HN-Q-8 fermentation was 7:3,the effect of promoting potato plant growth was the best.The volume ratio of mixture of thiafuracil-azoxystrobin and strain HN-Q-8 was 1:9 and 2:8,and the volume ratio of mixture of ningnanmycin-azoxystrobin and strain HN-Q-8 was 7:3,and the fermentation liquid of single strain HN-Q-8,thiafuracil-azoxystrobin,ningnanmycin-azoxystrobin and water was potted in greenhouse.The results showed that when the combination ratio of ningnanmycin-azoxystrobin and Bacillus velezensis HN-Q-8 fermentation was 7:3,the growth rate of plant height,stem circumference and root length were 53.62%,21.60%and 27.27%,respectively.4.The field control effect of mixture of ningnanmycin-azoxystrobin and Bacillus velezensis HN-Q-8 fermentation on potato black scurf was determined.In 2019,the control effect of mixture of ningnanmycin-azoxystrobin and Bacillus velezensis HN-Q-8 fermentation on potato moles was 85.94%.The control effect of compound agents was significantly higher than that of single-dose ningnanmycin-azoxystrobin and single-dose HN-Q-8 fermentation liquid.The results of field trials in 2020 showed that in five different control programs,the control effect of the control scheme Ⅰ(furrow application),the control scheme Ⅱ(furrow application+spraying at seedling stage)and the control schemeⅢ(furrow application+ spraying at seedling stage+spraying at bud stage)showed no significant difference.The control effect of compoud agents on canker stem and potato black scurf was 77.14%-82.86%and 91.67%-93.38%,respectively.The yield increasing rate was 24.05%-26.86%.As there was no significant difference in the control effect and yield increase rate between the control scheme Ⅰ(trench application),the control scheme Ⅱ(trench application+seedling spraying)and the control scheme Ⅲ(trench application+seedling spraying+ budding spraying),the control scheme Ⅰ(trench application)was recommended. |
PDF Full Text Request