Abstract
Rapeseed is an important oil crop strongly dependent on high agrochemical inputs. Some pathogens, including Leptosphaeria maculans, cause blackleg disease and can drastically decrease yields. Microbial inoculants seem to be a promising solution to these problems. However, a selection of potent bacterial strains able to improve growth and/or suppress disease is needed. Endophytic bacteria (n = 38) isolated from rapeseed plants with exceptionally good growth were screened for plant growth promoting (PGP) traits and L. maculans antifungal activity. A majority of isolates (35) showed the ability to produce siderophores, 17 isolates solubilized phosphate, and 28 isolates inhibited the growth of L. maculans. The six most promising isolates belonging to Bacillus genera were characterized in detail and compared to two previously published PGP strains. Plant growth measured as total weight and root length of rapeseed seedlings was stimulated by all isolates in comparison to control. The best isolate, 1L6, preliminary identified as Bacillus pumilus showed the highest phosphate solubilization, IAA and HCN production, and growth promotion of plants. Isolates with high antifungal activity in screening showed good potential to suppress disease on plants, with 87% reduction of lesions caused by L. maculans. These strains are good candidates to be explored under field use either solely or in combination.
Highlights
Rapeseed is widely cultivated in temperate climate regions mainly for the production of oily seeds used in human and animal nutrition [1]
The objective of this study was to evaluate the plant growth properties of endophytic bacteria isolated from rapeseed by analysis of Indole-3-acetic acid (IAA), Hydrogen cyanide (HCN) and siderophore production as well as phosphate solubilization, and by analysis of growth and pathogen development in inoculated rapeseed plants in comparison with previously described plant growth promoting bacteria (PGPB)
A total of 38 isolates of bacteria were isolated from surface sterilized roots, stems, and leaves of Brassica napus (Table 1)
Summary
Rapeseed is widely cultivated in temperate climate regions mainly for the production of oily seeds used in human and animal nutrition [1]. It is considered to be a serious global plant disease It occurs in epidemic proportions in most of the rapeseed producing regions in Europe [6,7]. Climate change may exacerbate the spread of the disease, as under experimental conditions, higher temperatures (15 ◦ C vs 10 ◦ C or 5 ◦ C) have been shown to reduce spore germination time and increase mycelium penetration efficiency [8,9]. Several strategies such as crop rotation, chemical control, sanitation, and resistant cultivars have been advised for blackleg control [10]. The perceived health and environmental risks of fungicide use resulted in increased interest in alternative disease management strategies
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