Phyllosphere microbiota play a crucial role in plant-environment interactions and their microbial community and function are influenced by biotic and abiotic factors. However, there is little research on how pathogens affect the microbial community of phyllosphere fungi. In this study, we collected 16 pumpkin (Cucurbita moschata) leaf samples which exhibited powdery mildew disease, with a severity ranging from L1 (least severe) to L4 (most severe). The fungal community structure and diversity was examined by Illumina MiSeq sequencing of the internal transcribed spacer (ITS) region of ribosomal RNA genes. The results showed that the fungal communities were dominated by members of the Basidiomycota and Ascomycota. The Podosphaera was the most dominant genus on these infected leaves, which was the key pathogen responsible for the pumpkin powdery mildew. The abundance of Ascomycota and Podosphaera increased as disease severity increased from L1 to L4, and was significantly higher at disease severity L4 (P < 0.05). The richness and diversity of the fungal community increased from L1 to L2, and then declined from L2 to L4, likely due to the biotic pressure (i.e., symbiotic and competitive stresses among microbial species) at disease severity L4. Our results could give new perspectives on the changes of the leaf microbiome at different pumpkin powdery mildew disease severity.

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The phyllosphere is colonized by a wide variety of microorganisms including epiphytes, plant-pathogenic fungus, bacteria, as well as human or animal pathogens. However, little is known about how microbial community composition changes with the development of angular leaf-spot of cucumber. Here, 18 mixed samples were collected based on the lesion coverage rate (LCR) of angular leaf-spot of cucumber from three disease severity groups (DM1: symptomatic-mild, DM2: symptomatic-moderate, DM3: symptomatic-severe). In our study, the microbial community structure and diversity were examined by Illumina MiSeq sequencing. A significant differences was observed in α diversity and community structure among three disease severity groups. The phyllosphere microbiota was observed to be dominated by bacterial populations from Proteobacteria, Actinobacteria, and Firmicutes, as well as fungal species from Ascomycota and Basidiomycota. In addition, some plant-specific microbe such as Sphingomonas , Methylobacterium , Pseudomonas , and Alternaria showed significant changes in their relative abundance of population. The LCR was correlated negatively with Sphingomonas , Methylobacterium , Quadrisphaera , and Lactobacillus , whereas correlated positively with Pseudomonas and Kineococcus (p < 0.05). The LCR was negatively correlated with Alternaria and Arthrinium of the fungal communities (p < 0.05). Molecular ecological networks of the microbial communities were constructed to show the interactions among the OTUs. Our current results indicated that the competitive relationships among species were broken with the development of angular leaf-spot of cucumber. The microbial community composition changed over the development of angular leaf-spot of cucumber. The result of molecular ecological networks indicated that the overall bacterial community tends toward mutualism from the competition. The development of angular leaf-spot of cucumber affected the ecosystem functioning by disrupting the stability of the microbial community network. This work will help us to understand the host plant-specific microbial community structures and shows how these communities change throughout the development of angular leaf-spot of cucumber. Electronic supplementary material The online version of this article (10.1186/s13568-019-0800-y) contains supplementary material, which is available to authorized users.

In recent years, the photosynthetic bacteria have been used widely in agriculture, but the effects of different agricultural applications on crop rhizosphere microorganism and crops are lack. In this study, we provide new insights into the structure and composition of the rice root-associated microbiomes as well as the effect on crop of the Rhodopseudomonas palustris(R. palustris) PSB06 and CGA009 at the rice seedling stage with seed immersion and root irrigation. Compare with CK group, the length of stem, the peroxidase (POD), and superoxide dismutase (SOD) activities in PSB06 treatment group was significantly higher, while the length of stem in CGA009 treatment group was significantly higher. The POD and SOD activities in CGA009 treatment groups only were higher slightly than the CK group. In the study, the dominant phyla were Proteobacteria (51.95–61.66%), Bacteroidetes (5.40–9.39%), Acidobacteria (4.50–10.52%), Actinobacteria (5.06–8.14%), Planctomycetes (2.90–4.48%), Chloroflexi (2.23–5.06%) and Firmicutes (2.38–7.30%), accounted for 87% bacterial sequences. The principal coordinate analysis (pCoA) and mantel results showed the two application actions of R. palustris CGA009 and PSB06 had significant effects on rice rhizosphere bacterial communities (p < 0.05). The PSB06 can significantly promote the rice growth and enhance stress resistance of rice at the seedling stage, while the R. palustris CGA009 has no significant effect on rice. Dissimilarity test and canonical correspondence analysis (CCA) results showed that the TN and pH were the key factors affecting rice rhizosphere bacterial community in the seedling stage. This study will provide some guidance advices for the study of the microecological regulation of photosynthetic bacteria on crops.

Purpose The application of fungicides is one of the main strategies to prevent clubroot disease. Currently, numerous studies focus on changes in the soil microbial community at different levels of clubroot disease severity. However, the effects of fungicides on the soil microbial community and causative pathogen, Plasmodiophora brassicae, while preventing clubroot disease remain unclear. Methods In this study, we evaluated the control efficacy of three fungicides (fluazinam, metalaxyl-mancozeb, and carbendazim) on clubroot disease of tumorous stem mustard in greenhouse experiment. Uninoculated and Water treatments after inoculation were performed as controls. At three (3 W) and six weeks (6 W) post-inoculation of P. brassicae, soil properties, bacterial composition (sequencing of 16S rRNA genes), and effector gene expression of the pathogen were analyzed. The correlation of these factors with disease index (DI) was explored. Results Fluazinam was the most effective in controlling clubroot disease of tumorous stem mustard with a controlled efficacy of 59.81%, and the abundance of P. brassicae in the soil decreased 21.29% after 3 weeks of treatment. Compared with other treatments, twelve out of twenty effector genes showed higher expression in fluazinam 3 W samples. Different fungicides had different effects on soil properties. EC (electrical conductivity), the main factor that positively associated with DI, was significantly lower in fluazinam treatment than the other two fungicide treatments. The application of fungicides, especially carbendazim, significantly reduced bacterial α-diversity and the composition of soil bacteria. Pseudomonas, Microbacterium, and Sphingobacterium (positively correlated with DI) were enriched in Water, metalaxyl-mancozeb, and carbendazim treatments, but were less abundant in fluazinam treatment. Among the three fungicide treatments, DI was significantly negatively correlated with Shannon and Chao 1 indices. Soil properties and the top bacterial genera that positively correlated with DI were influenced to a lesser degree in the fluazinam treatment. Conclusion Among three fungicides, fluazinam was the most effective agent with the highest control effects against clubroot disease. The strong virulence of fluazinam against P. brassicae was one of the main reasons for the prevention of clubroot disease, and in addition the alteration of rhizosphere bacterial community by fluazinam to the detriment of P. brassicae infection. Based on our results, EC could be an indicator of the severity of clubroot disease.

Phyllosphere microbiota play a crucial role in plant-environment interactions and are influenced by biotic and abiotic factors. However, there is little research on how pathogen s affect the microbial community. In this study, we collected 16 pumpkin (Cucurbita moschata) leaf samples showing symptoms of powdery mildew disease with different disease severity levels ranging from L1 (least severe) to L4 (most severe). We examined the fungal community structure and diversity by Illumina MiSeq sequencing of the internal transcribed spacer (ITS) region of ribosomal RNA genes. The fungal communities were dominated by members of the Basidiomycota and Ascomycota. The dominant genus was Podosphaera on the diseased leaves, which was the key pathogen responsible for the pumpkin powdery mildew. Ascomycota and Podosphaera increased in abundance as disease severity increased from L1 to L4, and were significantly more abundant than other microorganisms at disease severity L4 (P<0.05). The richness and diversity of the fungal community increased from L1 to L2, and then declined from L2 to L4, likely due to the biotic pressure at disease severity L4. Maintaining species richness in the phyllosphere will be an important part of managing disease control in this agroecological system and an essential step toward predictable biocontrol of powdery mildew in pumpkin. (Lebeda et al., 2010). 61The phyllosphere or leaf surface is an important microbial habitat for members of the major 62 bacterial and fungal groups, and Archaea (Lindow & Leveau, 2002; Lindow and Brandl, 2003).63 These microorganisms play a crucial role in helping their host against pathogens (Lacava et al., 64 2006; Mejía et al., 2008; Rajendran et al., 2008). In past years, most of the researchers focused 65 on screening plant growth-promoting microorganisms from plants which can help us manage 66 diseases (Compant et al., 2005;Everett et al., 2005;Hirano & Upper, 2000; Whipps et al., 67 2008). However, not all the microbes in the natural environment are considered culturable. In the 68 past few years, the development of next-generation rRNA sequencing techniques has enabled us 69 to obtain in-depth descriptions of the composition of the microbial communities associated with 70 leaves of Arabidopsis thaliana (Reisberg et al., 2013), potatoes (Becker et al., 2008), rice 71 (Mwajita et al., 2012), spinach (Lopez et al., 2011 Lopez et al., 2013), grape (Leveau et al., 72 2011, and various tree species including salt cedar (Redford et al., 2010;Finkel et al., 2011). 73Historically, scholars have begun to study the rhizosphere as a microbial habitat as early as 74 100 years ago (Hartmann et al., 2008) (Zhang et al., 2014). The phyllosphere microorganisms are influenced by 82 both biotic and abiotic factors, some of which are fairly stable and constant, such as habitat 83 conditions (Yang et al., 2016;Fonsecagarcía et al., 2016), the host genotype (Sapkota et al., 84 2015; Bodenhausen et al., 2014;Hunter et al., 2015), elevation gradient (Cordier et al., 2012; 85 Zh...

Patulibacter brassicae sp. nov., isolated from rhizosphere soil of Chinese cabbage (Brassica campestris) , was isolated from rhizosphere soil of Chinese cabbage in Shandong province, China. The cells were aerobic, Gram-staining-positive, oxidaseand catalase-positive, short rods and formed white colonies on trypticase soy agar. The cell-wall peptidoglycan contained meso-diaminopimelic acid as the diagnostic diamino acid and alanine, glutamic acid and leucine. Diphosphatidylglycerol was the predominant polar lipid. The predominant cellular fatty acid was C 18 : 1 !9c; minor components were anteiso-C 15 : 0 and anteiso-C 17 : 0 . The only isoprenoid quinone was demethylmenaquinone 7 (DMK-7), and the DNA G+C content was 72.7 mol%. Based on the full-length 16S rRNA gene sequence analysis, the closest phylogenetic neighbours of strain SD T were Patulibacter medicamentivorans DSM

Background Soybean-corn intercropping is widely practised by farmers in Southwest China. Although rhizosphere microorganisms are important in nutrient cycling processes, the differences in rhizosphere microbial communities between intercropped soybean and corn and their monoculture are poorly known. Additionally, the effects of cadmium (Cd) pollution on these differences have not been examined. Therefore, a field experiment was conducted in Cd-polluted soil to determine the effects of monocultures and soybean–corn intercropping systems on Cd concentrations in plants, on rhizosphere bacterial communities, soil nutrients and Cd availability. Plants and soils were examined five times in the growing season, and Illumina sequencing of 16S rRNA genes was used to analyze the rhizosphere bacterial communities. Results Intercropping did not alter Cd concentrations in corn and soybean, but changed soil available Cd (ACd) concentrations and caused different effects in the rhizosphere soils of the two crop species. However, there was little difference in bacterial community diversity for the same crop species under the two planting modes. Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria and Firmicutes were the dominant phyla in the soybean and corn rhizospheres. In ecological networks of bacterial communities, intercropping soybean (IS) had more module hubs and connectors, whereas intercropped corn (IC) had fewer module hubs and connectors than those of corresponding monoculture crops. Soil organic matter (SOM) was the key factor affecting soybean rhizosphere bacterial communities, whereas available nutrients (N, P, K) were the key factors affecting those in corn rhizosphere. During the cropping season, the concentration of soil available phosphorus (AP) in the intercropped soybean–corn was significantly higher than that in corresponding monocultures. In addition, the soil available potassium (AK) concentration was higher in intercropped soybean than that in monocropped soybean. Conclusions Intercropped soybean–corn lead to an increase in the AP concentration during the growing season, and although crop absorption of Cd was not affected in the Cd-contaminated soil, soil ACd concentration was affected. Intercropped soybean–corn also affected the soil physicochemical properties and rhizosphere bacterial community structure. Thus, intercropped soybean–corn was a key factor in determining changes in microbial community composition and networks. These results provide a basic ecological framework for soil microbial function in Cd-contaminated soil.