Bacillus sp. FJAT-55034: identification, growth characteristics, and antagonistic effect on Botryosphaeria dothidea causing pear ring rot

Abstract:

[Background] Pear ring rot caused by Botryosphaeria dothidea is one of the major diseases in pear cultivation, causing huge economic losses. [Objective] To identify the strain FJAT-55034 with high antagonistic activity against B. dothidea and evaluate its growth characteristics and antifungal activity, so as to provide an alternative strain for the biocontrol of pear ring rot. [Methods] Morphological characteristics, physiological and biochemical properties, and 16S rRNA gene sequencing were employed to identify the antagonistic strain FJAT-55034. Furthermore, we studied the growth characteristics of the strain by establishing the growth curve and determining the culture temperature and pH. The inhibition zone method was employed to determine the inhibitory spectrum of this strain. Finally, co-culture, microscopic observation, and pathogen inoculation in fruits were conducted to evaluate the antagonistic effect of strain FJAT-55034 on B. dothidea. [Results] The antagonistic strain FJAT-55034 was identified as Bacillus velezensis. It can survive at 20–50 ℃ (optimum 30 ℃) and pH 5.0–9.0 (optimum pH 7.0) and grow well with 0–5% NaCl. The strain exerted inhibitory effects on 6 pathogenic fungal species derived from fruit trees, with the inhibition zone diameters ranging from 19.8 mm to 29.1 mm. The inhibition rate of FJAT-55034 on the mycelial growth of B. dothidea was 77.2%. Moreover, the strain inhibited the expansion of pear ring rot with an inhibition rate of 66.0%. [Conclusion] The strain FJAT-55034 presented a desirable inhibitory effect on B. dothidea and served as an alternative strain for the biocontrol of pear ring rot.