Identification and control efficacy of Bacillus amyloliquefaciens sdf-005 against walnut anthracnose disease

Walnut anthracnose disease is a kind of serious disease of walnut all over the world. In China, this disease is caused by Colletotrichum gloeosporioides, which is hard to control. The long-term abusing of chemical fungicides will certainly pollute the soil and water, so it is urgent to find a new safe and effective method. Here, we describe the identification of antagonistic bacterial strain SDF-005 and its control efficacy. Based on morphology, physiological and biochemical characterizations and sequence analyses of 16S rDNA and gyrB, the strain SDF-005 could be classified as a strain of Bacillus amyloliquefaciens. The vitro antagonistic assay showed that this strain could distinctively suppress the growth of C. gloeosporioides and the inhibition zone diameter was 16.17 mm, with the inhibitive efficacy of 82.04%. In the normal condition, the inhibition rate of culture solution was 74.07%, but after the treatment in hot water of 85°C for 2 h, the inhibition rate decreased to 72.96%. However, there was no significant difference (P<0.01) between them. So, the antifungal substance of the strain had good heat-stability. After being treated at 121°C for 30 min, it still had the inhibition effect with the rate of 34.05%, which reduced significantly compared with above results. This showed that the strain of SDF-005 could generate some low content of bioactive compounds with small molecular and stable structure, which could inhibit the growth of mycelium. Affected by the metabolites, the structure of mycelium was destroyed, the hypha was enlarged, aberrant, twisted and the mycelial walls disintegrated. We also studied the control efficacy against the walnut anthracnose disease in the field, which showed that the control efficiency was both above 75% when diluting to 400 and 600 times. Therefore, the strain SDF-005 has a good application prospect on the biological control of walnut anthracnose disease.