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The plant rhizosphere is a major habitat for diverse microorganisms because of its heterogeneous microenvironment. It is well known that an imbalance in rhizosphere microorganisms has direct and indirect effects on soil fertility and plant health. In this study, we investigated the impact of Lysobacter antibioticus 13–6 seed coat treatment on the soil physicochemical properties, plant growth, and bacterial community composition of maize plants in both in vivo and in vitro experiments, using high-throughput amplicon sequencing of 16S rRNA. Under in vitro conditions, we determined that L. antibioticus 13–6 has the ability to solubilize P, hydrolyze cellulose, and synthesize indole acetic acid. Furthermore, under in vivo conditions, L. antibioticus 13–6 significantly improved the soil physicochemical properties and enhanced the root length, stalk height, dry weight of root and stalk, grain yield, and chlorophyll contents by successful colonization in the rhizosphere of maize plants. The results of high-throughput amplicon sequencing of 16S rRNA demonstrated that L. antibioticus 13–6 significantly changed the diversity and composition of the rhizosphere bacterial communities. The relative abundance of Gammaproteobacteria, Gemmatimonadetes, and Bacteroidetes at the phylum level and Streptomyces, Lysobacter, and Nitrospira at the genus level significantly increased in the rhizosphere of L. antibioticus 13–6 seed coat-treated plants. Co-occurrence networks analysis revealed that the rhizosphere of L. antibioticus 13–6 seed coat-treated plants had fewer negative correlations and less competition for resources among bacterial communities. Genome analysis of L. antibioticus 13–6 revealed that the genome of L. antibioticus 13–6 encodes genes related to indole acetic acid synthesis, chitinase decomposition, and P solubilization, making it one of the most potent plant growth-promoting bacteria. Overall, this study demonstrated the potential of L. antibioticus 13–6 as a promising seed coat bioagent for sustainable agriculture and to minimize the utilization of agrochemicals. [ABSTRACT FROM AUTHOR]

Simple Summary: Clubroot, caused by Plasmodiophora brassicae Woron, seriously affects cruciferous plants. The pathogen survives in the soil in the form of resting spores and infects crops for many generations. Currently, clubroot management relies on pesticides and resistant varieties with several limitations. Therefore, there is a need to devise environmentally friendly control measures to mitigate this devastating pathogen. The occurrence and damage of clubroot can be alleviated by microbial consortia. The biocontrol potential of Bacillus cereus BT-23, Lysobacter antibioticus 13-6, and Lysobacter capsici ZST1-2 was investigated as sole strains, intra-/inter-genus co-cultures, and microbial consortia for clubroot disease, plant growth, and rhizosphere bacterial diversity in a field experiment. The microbial consortia efficiently controlled the disease incidence with a successful biocontrol effect of about 65.78%, reshaped the rhizosphere's microbial diversity, and reduced the soil acidity. Thus, we conclude that microbial consortia suppress the disease incidence by recovering the imbalance in the indigenous microbial community composition. This study highlights the potential of microbial consortia as an engineering tool to control soilborne diseases by reshaping the rhizosphere microbiome. Clubroot disease, caused by Plasmodiophora brassicae, is a serious threat to Chinese cabbage (Brassica rapa subsp. pekinensis) production, which results in extensive yield losses. At present, clubroot control mainly depends upon pesticides, which provoke food-safety concerns, and the application of sole biocontrol agents cannot successfully control the disease. In this study, we investigated the effect of Bacillus cereus BT-23, Lysobacter antibioticus 13-6, and Lysobacter capsici ZST1-2 as sole strains, intra-/inter-genus co-culture, and microbial consortia on clubroot disease, plant growth, and rhizosphere bacterial diversity in a field experiment. The microbial consortia efficiently controlled the incidence of clubroot disease, with a biocontrol effect of about 65.78%, by decreasing the soil acidity and enhancing the yield (17,662.49 kg/acre). The high-throughput sequencing results demonstrated that the phyla Proteobacteria and Bacteroidetes were present in high relative abundance in the rhizosphere soil of the Chinese cabbage. Furthermore, Firmicutes was found as a unique phylum in the rhizosphere soil of CK-H and T1-T7, except for CK-D. The application of microbial consortia recovers the imbalance in indigenous microbial communities. Therefore, we conclude that microbial consortia can reduce the clubroot incidence in Chinese cabbage by decreasing the soil acidity and altering the diversity and structure of rhizosphere bacterial communities. This study highlights the potential of microbial consortia as an engineering tool to control devastating soilborne diseases in commercial crops. [ABSTRACT FROM AUTHOR]

Bacterial leaf streak (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc), impacts the production of rice. However, several rice cultivars displayed resistance to Xoc in the field, but scarce information is available about the role of endophytic microbiota in disease resistance. In the present study, the endophytic bacterial communities of resistant and susceptible rice cultivars "CG2" and "IR24", respectively, were analyzed using high throughput 16S rRNA gene amplified sequencing and culture dependent method was further used for bacterial isolation. A total of 452,716 high-quality sequences representing 132 distinct OTUs (Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes) and 46 isolates of 16 genera were explored from rice leaves infected with Xoc. Community diversity of endophytic bacteria were higher in the leaves of the resistant cultivars compared to susceptible cultivars upon Xoc infection. Strikingly, this diversity might contribute to natural defense of the resistant cultivar against pathogen. Pantoea, which is pathogen antagonist, was frequently detected in two cultivars and higher abundance were recorded in resistant cultivars. Different abundance genus includes endophytic isolates with marked antagonistic activity to Xoc. The increased proportions of antagonistic bacteria, may contribute to resistance of rice cultivar against Xoc and the Pantoea genus was recruited by Xoc infection play a key role in suppressing the development of BLS disease in rice. Taken together, this work reveals the association between endophytic bacteria and BLS resistance in rice and identification of antagonism-Xoc bacterial communities in rice. [ABSTRACT FROM AUTHOR]

The endophytic microbiome plays an important role in plant health and pathogenesis. However, little is known about its relationship with bacterial blight (BB) of rice caused by Xanthomonas oryzae pv. oryzae (Xoo). The current study compared the community compositional structure of the endophytic microbiota in healthy and BB symptomatic leaves of rice through a metabarcoding approach, which revealed BB induced a decrease in the alpha-diversity of the fungal communities and an increase in the bacterial communities. BB-diseased rice leaves were enriched with saprophytic fungi that are capable of decomposing plant cell walls (e.g. Khuskia spp. and Leptosphaerulina spp.), while healthy rice leaves were found to be significantly more abundant with plant pathogens or mycotoxin-producing fungi (e.g. Fusarium , Magnaporthe , and Aspergillus). The endophytic bacterial communities of BB-diseased leaves were significantly enriched with Pantoea , Pseudomonas , and Curtobacterium , strains. Pantoea sp. isolates from BB leaves are identified as promising candidates for the biocontrol of BB for their ability to inhibit in vitro growth of Xoo , suppress the development of rice BB disease, and possess multiple PGP characteristics. Our study revealed BB-induced complexed changes in the endophytic fungal and bacterial communities of rice leaves and demonstrated that BB-associated enrichment of some endophytic bacterial taxa, e.g. Pantoea sp. isolates, may play important roles in suppressing the development of BB disease in rice. [ABSTRACT FROM AUTHOR]