Annual Research & Review in Biology

Aims: To investigates whether a new bio control agent Bacillus amyloliquefaciens CC09 can be used to manage the root rot disease of Rehmannia glutinosa resulting from continuous cropping.
Study Design: Completely randomized block experiments with 3 replicates were conducted in the field where R. glutinosa had been grown for one-year.
Place and Duration of Study: Yangyue village, Linfen city, Shanxi province, from April 11 to September 21, 2010.
Methodology: Four treatments were performed in the trial: T1, seeds were soaked in the bio control agent strain CC09 for 30min; T2: spreading 50 ml of the bio control agent per area right before seed down; T3: seeds were soaked in 1000-fold dilution solution of of 80% carbendazim WP for 30min; T4: seeds were soaked in fresh water for 30min. The incidence of root rot disease (IRRD), disease severity (DS), disease index (DI), relative disease control efficiency (RDCE), the relative yield increase (RYI) and the soil bacterial population were investigated. The dynamics of rifr strain CC0910 in soil were performed in Petri dishes using the culture dependent method.
Results: Compared with blank control at harvest time, we observed not only 55.5% of disease control efficacy but also 28.6% yield increase in T1 treatment, 43.4% and 39.9% in T2 treatment. With the aid of rif^r mutant CC0910 and culture-dependent method, we found the soil bacterial populations significant higher in T2 than that in T1 (P<0.05). Moreover, the strain CC09 in soil increased to the maximum in the first few days and then decreased to a relative stable density of 5×10⁷ cells g^-1.
Conclusion: As the new bio control agent CC09 can maintain high cell density in the soil, thus it could be used to control the root rot disease of R. glutinosa caused by continuous cropping.