| Potato scab is mainly caused by Streptomyces spp.and occurs in potato growing areas all over the world.The disease is mainly harmful to potato tubers,which can form woody lesions on the surface.It seriously affects the quality of the potato,reduces market competitiveness,and causes economic losses.In addition to infecting potatoes,this pathogens that cause potato scab can also infect other hosts such as beets,radishes,carrots and so on.In recent years,potato scab have occurred successively in many potato production areas in China.Gansu Province is the main potato planting area in China.The occurrence of this disease has been increasing year by year,which has seriously affected the development of the potato industry in Gansu province.The pathogens of potato scab in Dingxi City of Gansu Province were isolated and identified in this paper.Their biological characteristics were determined,antagonistic bacteria were screened,and the fermentation conditions of excellent antagonistic strains were optimized.At the same time,the best control agent of potato scab was screened through the field pesticide control test.The main conclusions are as follows:1.20 strains of actinomycete isolates were isolated from the potato collected from Dingxi City,Gansu Province by tissue separation method.By pathogenicity determination,2 strains named 5A-1 and 5T-1 with strong pathogenicity were obtained.Combined with morphological features and 16S rDNA sequence analysis,they were identified as Streptomyces griseoplanus and Streptomyces galilaeus respectively.The two pathogens causing potato scab were reported for the first time in China and Gansu province,respectively..Biological characteristics of strains 5A-1 and5T-1 were optimized for growth at 25°C and 30°C,optimal growth conditions for light were all dark,optimum growth pH was 8.5,and multiple carbon and nitrogen sources could be used to grow.2.The strains with the strongest antagonism to pathogenic strains named 5A-1and 5T-1 were 3-5 and 8-4,which were respectively selected from 131 strains of potato endophytic bacteria.And the antibacterial bandwidths were 25.73 mm and 11.3mm,respectively.Combined with morphological observation and molecular biological identification,strains 3-5 and 8-4 were identified as Bacillus amyloliquefaciens and Bacillus velezensis,respectively.3.The optimum fermentation carbon and nitrogen source of strain 8-4 were glucose and yeast extract respectively.The optimal fermentation conditions of strain3-5 were that initial pH was 8.5,temperature was 28°C,rotational speed was200r/min,inoculation amount was 14%,and fermentation time was 36h;The optimum fermentation carbon and nitrogen source of strain 8-4 were soluble starch and yeast extract respectively.The optimum fermentation conditions of strain 8-4were that initial pH was 6,temperature was 32°C,rotational speed was 120 r/min,inoculation amount was 14%,and fermentation time was 24h.4.Nine kinds of fungicides and five kinds of bacterial fertilizers for the prevention and treatment of potato scab were selected in the field pesticide control test.The results showed that except for 24%thifluzamide 15ml/667m~2,250g/L tebuconazole 5ml/667m~2 and 300g/L kresoxim-methly-boscalid 5ml/667m~2,all other fungicide treatments had certain effects on potato scab,especially 77%copper calcium sulphate 12.5ml/667m~2 the best control effect.Bacterial liquid A1,bacteria solution complex 3,mixed bacterial fertilizer(262AG6+262XY2+263XY3)and bacteriophage fertilizer ZA1 were all more effective than fungicides treatment(except copper calcium sulphate),so they could be used as prevention of potato scab in green bacterial fertilizers.The results of the trials at the harvest showed that the most obvious treatment to increase potato yield was 1,2-benzothiazole-3-copper30ml/667m~2 treatment.Taking comprehensive consideration of control efficiency and yieldincreaseissues,itwasconcludedthatmixedbacterialfertilizer(262AG6+262XY2+263XY3)and 77%copper calcium sulphate are the best control agents for preventing potato scab. |
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