Biocontrol of PGPR strain Bacillus amyloliquefaciens Ba168 against Phytophthora nicotianae on tobacco

Abstract

Abstract： 9Tobacco black shank (TBS) caused by Phytophthora nicotianae is destructive to almost all 10 kinds of tobacco cultivars and is widespread in many tobacco-planted countries. Here, an isolated 11 plant growth-promoting rhizobacteria (PGPR) strain Ba168 is promise in biocontrol of TBS. In 12 vitro assays disclosed a strong P. nicotianae suppression activity and the field utilization potential 13 (FUP) by characterized the crude extract of culture filtrates of Ba168. P. nicotianae's growth was 14 inhibited by the crude extract at minimum inhibitory concentration (MIC) of 5μl/mL. Extracellular 15 conductivity, pH and the wet, dry weight of P. nicotianae's mycelia, were significantly different 16 after treated with different concentrations of the crude extract and the deformity and perforation of 17 treated P. nicotianae's hyphae can be observed in scanning electron microscope (SEM) analysis. 18Proteome characterizations of the crude extract were used as supplementary proofs that further 19 evaluated FUP of Ba168. We then identified strain Ba168 as B. amyloliquefaciens by its genetic 20 and phenotypic characteristics. Field assays comparatively evaluated TBS control efficacy of these 21PGPRs and agrochemicals. Pooling analysis of the results showed that the biocontrol efficacy of 22Ba168 preparation is only lower than Mixture of Propamocarb hydrochloride and Azoxystrobin 23 (MPA) but better than other tested subjects. Although the existence of differences in biocontrol 24 efficacy, PGPR preparations effectively reduced the disease index of tobacco. 25