A study on control of cucumber seedling diseases with a compound biological seed coating agent
[Objective]A compound biological seed coating agent was prepared with Paenibacillus polymyxa P6 and Peptaibols to control the diseases of damping-off,root rotandrhizoctonia stem rot during cucumber seed germination and seedling stages.[Method](1)An in vitro test was conducted to screen the biocontrol strains and the concentration of Peptaibols with effective antagonistic activities against the pathogens of Pythiumap aphanidermatum,Fusarium solani and Rhizoctonia solani causing the diseases.(2)A further screening test was carried out to check if the biocontrol strains were compatible with Peptaibols used in certain concentrations;(3)A bioassay was conducted to test the effectiveness of the compound seed coating agent on seed germination of cucumber and control of the diseases.[Result]The inhibition rates to P.ahanidermatum,F.solani and R.solani were raised with the increase of Peptaibols concentration,and the inhibition rates to both P.ahanidermatum and F.solani reached 100%when the applied concentrations were at 50 mg/L and 200 mg/L,respectively,and that to R.solani reached 69.00%when the applied concentration was at 200 mg/L.The results of compatibility test showed that P6 could be compatible well with Peptaibols when the applied concentration was at 32.5 mg/L,and combining P6 and Peptaibols to form a compound seed coating agent,the inhibition rates of it to the pathogens of P.ahanidermatum,F.solani and R.solani were 90.8%,59.7%and 90.6%,respectively,which were significantly better than that of Peptaibols or P6 used alone.The results of the bioassay showed that the treatment with the compound seed coating agent containing 106 cfu/g of P6 and 32.5 mg/L of Peptaibols were superior to that of P6 or Peptaibols used alone for controlling the three seedling diseases,and the control effective rates were 38.67%,57.00%and 72.23%,respectively.[Conclusion]P6 has a broad spectrum antagonistic activity.It can be compatible well with Peptaibols to form a stable compound seed coating agent,which can effectively control the seedling diseases of cucumber.
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