Deciphering the Bacillus amyloliquefaciens B9601-Y2 as a Potential Antagonist of Tobacco Leaf Mildew Pathogen During Flue-Curing

Effects of transgenic modification on the bacterial communities in different niches of maize under glyphosate toxicity

Transgenic glyphosate-resistant maize has emerged as a way to expand the use of glyphosate for weed control. Studying the microbiome in the tissues and rhizosphere soil of transgenic plants is vital for understanding the glyphosate-resistant mechanism and optimizing the transgenic design of crops. In our study, the expression of a mutant cp4epsps gene in transgenic maize, which confers tolerance to glyphosate, was performed using the maize variety Xianyu 335 as the genetically modified acceptor line. This transgenic modification did not affect the initial bacterial community in the leaf, stem, or root of maize, but promoted a differential bacterial community in the rhizosphere soil. Under glyphosate application, the abundance of beneficial bacteria involved in N fixation and P solubilization in plant tissues and the rhizosphere soil of glyphosate-resistance maize were higher than those in the glyphosate-sensitive maize. In contrast, the abundance of pathogens had the opposite trend, suggesting that the enhanced health of transgenic maize prevented microbiome deterioration under glyphosate. The re-inoculation of bacterial strains isolated from glyphosate-resistance maize into the leaf and rhizosphere soil of glyphosate-sensitive maize resulted in an enhanced photosynthetic capacity in response to glyphosate, demonstrating the vital role of specific bacteria for glyphosate resistance. Our study provides important evidence of how transgenic maize tolerance to herbicides affects the bacterial communities across the maize niches under glyphosate toxicity.

BioSolutions for Green Agriculture: Unveiling the Diverse Roles of Plant Growth-Promoting Rhizobacteria

The extensive use of chemical pesticides and fertilizers in conventional agriculture has raised significant environmental and health issues, including the emergence of resistant pests and pathogens. Plant growth-promoting rhizobacteria (PGPR) present a sustainable alternative, offering dual benefits as biofertilizers and biocontrol agents. This review delves into the mechanisms by which PGPR enhance plant growth, including nutrient solubilization, phytohormone production, and pathogen suppression. PGPR's commercial viability and application, particularly under abiotic stress conditions, are also examined. PGPR improves plant growth directly by enhancing nutrient uptake and producing growth-promoting substances and indirectly by inhibiting phytopathogens through mechanisms such as siderophore production and the secretion of lytic enzymes. Despite their potential, the commercialization of PGPR faces challenges, including strain specificity, formulation stability, and regulatory barriers. The review highlights the need for ongoing research to deepen our understanding of plant-microbe interactions and develop more robust PGPR formulations. Addressing these challenges will be crucial for integrating PGPR into mainstream agricultural practices and reducing reliance on synthetic agrochemicals. The successful adoption of PGPR could lead to more sustainable agricultural practices, promoting healthier crops and ecosystems.

Biological Control of Verticillium Wilt and Growth Promotion in Tomato by Rhizospheric Soil-Derived Bacillus amyloliquefaciens Oj-2.16

Verticillium wilt disease caused by Verticillium dahliae seriously affects tomato quality and yield. In this work, strain Oj-2.16 was isolated from rhizosphere soil of the medicinal plant Ophiopogon japonicas and identified as Bacillus amyloliquefaciens on the basis of morphological, physiological, and biochemical characteristics and 16S rDNA sequencing. Strain Oj-2.16 exhibited a high inhibition rate against V. dahliae, and the hyphae inhibited by Oj-2.16 were found to be destroyed on scanning electron microscopy. Lipopeptide and dipeptide genes were detected in the Oj-2.16 genome by PCR amplification involved in surfactin, iturin, fengycin, and bacilysin biosynthesis. In pot experiments, the biocontrol efficacy of strain Oj-2.16 against Verticillium wilt in tomato was 89.26%, which was slightly higher than the efficacy of the chemical fungicide carbendazim. Strain Oj-2.16 can produce indole acetic acid, siderophores, assimilate various carbon sources, and significantly promoted the growth of tomato seedlings by increasing plant height, root length, stem width, fresh weight, and dry weight by 44.44%, 122.22%, 80.19%, 57.65%, 64.00%, respectively. Furthermore, defense-related antioxidant CAT, SOD, POD, and PAL enzyme activities significantly increased and MDA contents significantly decreased in tomato seedlings treated with strain Oj-2.16 upon inoculation of V. dahliae compared with the pathogen-inoculated control. In summary, we concluded that B. amyloliquefaciens Oj-2.16 could be used as a promising candidate for the biocontrol of Verticillium wilt and as plant growth stimulator of tomato.

Bacillus velezensis SYL-3 suppresses Alternaria alternata and tobacco mosaic virus infecting Nicotiana tabacum by regulating the phyllosphere microbial community

The occurrence of plant diseases is closely associated with the imbalance of plant tissue microecological environment. The regulation of the phyllosphere microbial communities has become a new and alternative approach to the biological control of foliar diseases. In this study, Bacillus velezensis SYL-3 isolated from Luzhou exhibited an effective inhibitory effect against Alternaria alternata and tobacco mosaic virus (TMV). The analysis of phyllosphere microbiome by PacBio sequencing indicated that SYL-3 treatment significantly altered fungal and bacterial communities on the leaves of Nicotiana tabacum plants and reduced the disease index caused by A. alternata and TMV. Specifically, the abundance of P. seudomo, Sphingomonas, Massilia, and Cladosporium in the SYL-3 treatment group increased by 19.00, 9.49, 3.34, and 12.29%, respectively, while the abundances of Pantoea, Enterobacter, Sampaiozyma, and Rachicladosporium were reduced. Moreover, the abundance of beneficial bacteria, such as Pseudomonas and Sphingomonas, was negatively correlated with the disease indexes of A. alternata and TMV. The PICRUSt data also predicted the composition of functional genes, with significant differences being apparent between SYL-3 and the control treatment group. Further functional analysis of the microbiome also showed that SYL-3 may induce host disease resistance by motivating host defense-related pathways. These results collectively indicate that SYL-3 may suppress disease progression caused by A. alternata or TMV by improving the microbial community composition on tobacco leaves.