Abstract
BackgroundTomato plant growth is frequently hampered by a high susceptibility to pests and diseases. Traditional chemical control causes a serious impact on both the environment and human health. Therefore, seeking environment-friendly and cost-effective green methods in agricultural production becomes crucial nowadays. Plant Growth Promoting Rhizobacteria (PGPR) can promote plant growth through biological activity. Their use is considered to be a promising sustainable approach for crop growth. Moreover, a vast number of biosynthetic gene clusters (BGCs) for secondary metabolite production are being revealed in PGPR, which helps to find potential anti-microbial activities for tomato disease control.ResultsWe isolated 181 Bacillus-like strains from healthy tomato, rhizosphere soil, and tomato tissues. In vitro antagonistic assays revealed that 34 Bacillus strains have antimicrobial activity against Erwinia carotovora, Pseudomonas syringae; Rhizoctonia solani; Botrytis cinerea; Verticillium dahliae and Phytophthora infestans. The genomes of 10 Bacillus and Paenibacillus strains with good antagonistic activity were sequenced. Via genome mining approaches, we identified 120 BGCs encoding NRPs, PKs-NRPs, PKs, terpenes and bacteriocins, including known compounds such as fengycin, surfactin, bacillibactin, subtilin, etc. In addition, several novel BGCs were identified. We discovered that the NRPs and PKs-NRPs BGCs in Bacillus species are encoding highly conserved known compounds as well as various novel variants.ConclusionsThis study highlights the great number of varieties of BGCs in Bacillus strains. These findings pave the road for future usage of Bacillus strains as biocontrol agents for tomato disease control and are a resource arsenal for novel antimicrobial discovery.
Highlights
Tomato plant growth is frequently hampered by a high susceptibility to pests and diseases
28 endophytic strains were isolated from healthy tomato plant tissues collected in Spain. 74 and 79 rhizosphere bacteria strains were isolated from tomato plants collected in Spain and the Netherlands, respectively
This work showed that 10 Bacillus and Paenibacillus strains, selected from 181 isolated Bacillus-like strains from the rhizosphere soil of healthy tomato plants and their tissues, have strong in vitro antagonistic activity against tomato bacterial, fungal and oomycetal pathogens
Summary
Tomato plant growth is frequently hampered by a high susceptibility to pests and diseases. The rhizosphere, a narrow zone of soil that surrounds and is influenced by plant roots, gives home to an overwhelming variety of organisms, in particular microorganisms such as bacteria, fungi, oomycetes, archaea, protozoa and algae [5, 6]. This complex microbial community has profound effects on plant growth since it facilitates nutrient absorption and provides health protection to plants [7]. They can promote plant growth either indirectly by suppression of diseases with secreted antimicrobials or directly by the improvement of physiological metabolic processes such as N2 fixation, phosphate solubilization and IAA production [8]
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