Roseomonas populi sp. nov., an acetate-degrading bacteria isolated from the stem of Populus tomentosa.

Strain CN29T, isolated from the stem of 5- to 6-year-old Populus tomentosa in Shandong, China, was characterized using a polyphasic taxonomic approach. Cells of CN29T were Gram-stain negative, aerobic, nonspore-forming, and nonmotile coccoid. Growth occurred at 20-37 °C, pH 4.0-9.0 (optimum, pH 6.0), and with 0-1% NaCl (optimum, 1%). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain CN29T was closely related to members of the genus Roseomonas and closest to Roseomonas pecuniae N75T (96.6%). This classification was further supported by phylogenetic analysis using additional core genes. The average nucleotide identity and digital DNA‒DNA hybridization values between strain CN29T and Roseomonas populi CN29T were 82.7% and 27.8%, respectively. The genome size of strain CN29T was 5.87 Mb, with a G + C content of 70.9%. The major cellular fatty acids included summed feature 8 (C18:1 ω7c/C18:1 ω6c), C19:0 cyclo ω8c and C16:0. The major respiratory quinone was Q-10. The polar lipids were phosphatidylcholine, aminolipid, phosphatidylglycerol, and diphosphatidylglycerol. Strain CN29T can utilize acetate as a carbon source for growth and metabolism. Additionally, it contains acid phosphatase (2-naphthyl phosphate), which catalyzes the hydrolysis of phosphoric monoesters. The CN29T strain contains several genes, including maeB, gdhB, and cysJ, involved in carbon, nitrogen, and sulfur cycling. These findings suggest that the strain may actively participate in ecosystem cycling, leading to soil improvement and promoting the growth of poplar trees. Based on the phylogenetic, phenotypic, and genotypic characteristics, strain CN29T is concluded to represent a novel species of the genus Roseomonas, for which the name Roseomonas populi sp. nov. is proposed. The type strain is CN29T (= JCM 35579T = GDMCC 1.3267T).

Flavobacterium endoglycinae sp. nov., an endophytic bacterium isolated from soybean (Glycine max L. cv. Gwangan) stems.

A Gram-stain-negative, facultatively anaerobic, motile by gliding, rod-shaped, oxidase- and catalase-positive bacterial strain, designated BB8T, was isolated from the stems of a Korean soybean cultivar (Glycine max L. cv. Gwangan). The strain produced a yellow pigment on tryptic soy agar. Growth of strain BB8T occurred at pH 5.0-8.0 (optimum, pH 7.0), at 10-35 °C (optimum, 25-30 °C) and in the presence of 0-1 % (w/v) NaCl (optimum, 0.5%). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain BB8T formed a lineage within the genus Flavobacterium and was most closely related to Flavobacterium artemisiae SYP-B1015T (96.9 % 16S rRNA gene sequence similarity) and Flavobacterium ustbae T13T (96.8%). The complete genome sequence of strain BB8T was 5 513 159 bp long with a G+C content of 34.1 mol%. The major fatty acids (>10 %) of strain BB8T were iso-C15 : 0 (21 %), summed feature 3 (comprising C16 : 1 ω7c and/or C16 : 1 ω6c, 20.3%) and iso-C16 : 0 3-OH (13.7%). The predominant polar lipids were phosphatidylethanolamine and unidentified aminolipids, and the major respiratory quinone was menaquinone-6. Based on these phenotypic, genotypic and chemotaxonomic characteristics, strain BB8T is considered to represent a novel species of the genus Flavobacterium, for which the name Flavobacterium endoglycinae sp. nov. is proposed. The type strain is BB8T (=KCTC 82167T=CCTCC AB 2020070T).

Comparison of the Responses of Soil Fungal Community to Straw, Inorganic Fertilizer, and Compost in a Farmland in the Loess Plateau.

The Loess Plateau is located in the arid and semi-arid regions in northern China. The ecosystem is particularly sensitive to natural and anthropogenic disturbances. Fungi can produce extracellular enzymes, decompose a variety of organic matter, and regulate carbon and nutrient balance. We studied the changes of soil fungal community compositions in response to straw, inorganic fertilizer, and compost in a typical farmland in the Loess Plateau. Our results demonstrated that the addition of straw significantly reduces the Shannon index of the fungal community, in addition, the participation of straw significantly affects the composition of the fungal community. Functional prediction based on FUNGuild showed that straw significantly reduced the relative abundance of saprotrophs, pathotrophs, symbiotrophs, lichenized, ectomycorrhizal, and plant pathogens. Although fertilization practices destroyed the co-occurrence pattern among the fungal species, the addition of straw alleviated this affect. No significant effect of straw, compost, and inorganic fertilizers on the co-occurrence pattern among species in the soil fungal community was observed. Compared with compost and inorganic fertilizer, the addition of straw shaped the community composition by changing the relative abundance of fungal functional taxa. Thus, in the fragile Loess Plateau environment, over-fertilizing or non-order-fertilizing may destroy the co-occurrence pattern of the fungal communities and Loess Plateau ecosystem. IMPORTANCE Determining the response of soil fungi in sensitive ecosystems to external environmental disturbances is an important, yet little-known, topic in microbial ecology. In this study, we evaluated the impact of traditional fertilization management practices on the composition, co-occurrence pattern, and functional groups of fungal communities in loessial soil. Our results show that in the fragile Loess Plateau environment, fertilizer management changed the composition of the fungal community and disrupted the co-occurrence pattern between fungi. The application of straw alleviates the destroying of the co-occurrence pattern. The current research emphasizes the necessity of rational fertilization of farmland in loessial soil.

Genetic diversity, antifungal evaluation and molecular docking studies of Cu-chitosan nanoparticles as prospective stem rust inhibitor candidates among some Egyptian wheat genotypes.

Wheat has a remarkable importance among cereals worldwide. Wheat stem and leaf rust constitute the main threats that destructively influence grain quality and yield production. Pursuing resistant cultivars and developing new genotypes including resistance genes is believed to be the most effective tool to overcome these challenges. This study is the first to use molecular markers to evaluate the genetic diversity of eighteen Egyptian wheat genotypes. Moreover, the molecular docking analysis was also used to assess the Cu-chitosan nanoparticle (CuChNp) treatment and its mode of action in disease control management. The tested genotypes were categorized into two main cluster groups depending on the similarity matrix, i.e the most resistant and susceptible genotypes to stem and leaf rust races. The results of SCoT primers revealed 140 polymorphic and 5 monomorphic bands with 97% polymorphism. While 121 polymorphic and 74 monomorphic bands were scored for SRAP primers (99% polymorphism). The genotypes Sakha 94, Sakha 95, Beni Sweif 4, Beni Sweif 7, Sohag 4 and Sohag 5 were resistant, while Giza 160 was highly susceptible to all stem rust races at the seedling stage. However, in the adult stage, the 18 genotypes were evaluated for stem and leaf rust-resistant in two different locations, i.e. Giza and Sids. In this investigation, for the first time, the activity of CuChNp was studied and shown to have the potential to inhibit stem and leaf rust in studied Egyptian wheat genotypes. The Spraying Cu-chitosan nanoparticles showed that the incubation and latent periods were increased in treated plants of the tested genotypes. Molecular modeling revealed their activity against the stem and leaf rust development. The SRAP and SCoT markers were highly useful tools for the classification of the tested wheat genotypes, although they displayed high similarities at the morphological stage. However, Cu-chitosan nanoparticles have a critical and effective role in stem and leaf rust disease control.

Sulfur Induces Resistance against Canker Caused by Pseudomonas syringae pv. actinidae via Phenolic Components Increase and Morphological Structure Modification in the Kiwifruit Stems.

Bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa) has led to considerable losses in all major kiwifruit-growing areas. There are no commercial products in the market to effectively control this disease. Therefore, the defense resistance of host plants is a prospective option. In our previous study, sulfur could improve the resistance of kiwifruit to Psa infection. However, the mechanisms of inducing resistance remain largely unclear. In this study, disease severity and protection efficiency were tested after applying sulfur, with different concentrations in the field. The results indicated that sulfur could reduce the disease index by 30.26 and 31.6 and recorded high protection efficiency of 76.67% and 77.00% after one and two years, respectively, when the concentration of induction treatments was 2.0 kg/m3. Ultrastructural changes in kiwifruit stems after induction were demonstrated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the activities of phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO), and the accumulation of lignin were determined by biochemical analyses. Our results showed that the morphological characteristics of trichomes and lenticels of kiwifruit stem were in the best defensive state respectively when the sulfur concentration was 3.0 kg/m3 and 1.5 kg/m3. Meanwhile, in the range of 0.5 to 2.0 kg/m3, the sulfur could promote the chloroplast and mitochondria of kiwifruit stems infected with Psa to gradually return to health status, increasing the thickness of the cell wall. In addition, sulfur increased the activities of PAL, POD and PPO, and promoted the accumulation of lignin in kiwifruit stems. Moreover, the sulfur protection efficiency was positively correlated with PPO activity (p < 0.05) and lignin content (p < 0.01), which revealed that the synergistic effect of protective enzyme activity and the phenolic metabolism pathway was the physiological effect of sulfur-induced kiwifruit resistance to Psa. This evidence highlights the importance of lignin content in kiwifruit stems as a defense mechanism in sulfur-induced resistance. These results suggest that sulfur enhances kiwifruit canker resistance via an increase in phenolic components and morphology structure modification in the kiwifruit stems. Therefore, this study could provide insights into sulfur to control kiwifruit canker caused by Psa.

Mixed Transcriptome Analysis Revealed the Possible Interaction Mechanisms between Zizania latifolia and Ustilago esculenta Inducing Jiaobai Stem-Gall Formation.

The smut fungus Ustilago esculenta infects Zizania latifolia and induces stem expansion to form a unique vegetable named Jiaobai. Although previous studies have demonstrated that hormonal control is essential for triggering stem swelling, the role of hormones synthesized by Z. latifolia and U. esculenta and the underlying molecular mechanism are not yet clear. To study the mechanism that triggers swollen stem formation, we analyzed the gene expression pattern of both interacting organisms during the initial trigger of culm gall formation, at which time the infective hyphae also propagated extensively and penetrated host stem cells. Transcriptional analysis indicated that abundant genes involving fungal pathogenicity and plant resistance were reprogrammed to maintain the subtle balance between the parasite and host. In addition, the expression of genes involved in auxin biosynthesis of U. esculenta obviously decreased during stem swelling, while a large number of genes related to the synthesis, metabolism and signal transduction of hormones of the host plant were stimulated and showed specific expression patterns, particularly, the expression of ZlYUCCA9 (a flavin monooxygenase, the key enzyme in indole-3-acetic acid (IAA) biosynthesis pathway) increased significantly. Simultaneously, the content of IAA increased significantly, while the contents of cytokinin and gibberellin showed the opposite trend. We speculated that auxin produced by the host plant, rather than the fungus, triggers stem swelling. Furthermore, from the differently expressed genes, two candidate Cys2-His2 (C2H2) zinc finger proteins, GME3058_g and GME5963_g, were identified from U. esculenta, which may conduct fungus growth and infection at the initial stage of stem-gall formation.

Detecting Phytophthora cinnamomi associated with dieback disease on Carya cathayensis using loop-mediated isothermal amplification.

Chinese hickory (Carya cathayensis Sarg.) is an economically and ecologically important nut plant in China. Dieback and basal stem necrosis have been observed in the plants since 2016, and its recent spread has significantly affected plant growth and nut production. Therefore, a survey was conducted to evaluate the disease incidence at five sites in Linan County, China. The highest incidence was recorded at the Tuankou site at up to 11.39% in 2019. The oomycete, Phytophthora cinnamomi, was isolated from symptomatic plant tissue and plantation soil using baiting and selective media-based detection methods and identified. Artificial infection with the representative P. cinnamomi ST402 isolate produced vertically elongated discolorations in the outer xylem and necrotic symptoms in C. cathayensis seedlings in a greenhouse trial. Molecular detections based on loop-mediated isothermal amplification (LAMP) specific to P. cinnamomi ST402 were conducted. Result indicated that LAMP detection showed a high coherence level with the baiting assays for P. cinnamomi detection in the field. This study provides the evidence of existence of high-pathogenic P. cinnamomi in the C. cathayensis plantation soil in China and the insights into a convenient tool developed for conducting field monitoring of this aggressive pathogen.

Optimization of factors affecting the rooting of pine wilt disease resistant Masson pine (Pinus massoniana) stem cuttings.

Pine wilt disease (PWD) is a devastating disease affecting trees belonging to the genus Pinus. To control the spread of PWD in the Masson pine forest in China, PWD resistant Masson pine clones have been selected by the Anhui Academy of Forestry. However, because Masson pine is a difficult-to-root species, producing seedlings is challenging, especially from trees older than 5 years of age, which impedes the application of PWD resistant clones. In this study, we investigated the factors affecting rooting of PWD resistant clones and established a cheap, reliable, and simple method that promotes rooting. We tested the effects of three management methods, four substrates, two cutting materials, two cutting treatments, and three collection times on the rooting of cuttings obtained from 9-year-old PWD resistant clones. Rooting was observed only in stem cuttings treated with the full-light automatic spray management method. Additionally, stem cuttings showed a significantly higher rooting rate and root quality than needles cuttings. Compared with other substrates, stem cuttings planted in perlite produced the longest adventitious root and the highest total root length and lateral root number. Moreover, stem cuttings of PWD resistant clones collected in May showed a significantly higher rooting rate and root quality than those collected in June and July. Moreover, stem cuttings prepared with a horizontal cut while retaining the needles showed significantly higher rooting rate and root quality than those prepared with a diagonal cut while partly removing the needles. This study promotes the reproduction of seedlings of PWD-resistant Masson pine clones which helps control the spread of PWD, meanwhile, provides a technical reference for the propagation of mature pine trees via cuttings.

A recombined Sr26 and Sr61 disease resistance gene stack in wheat encodes unrelated NLR genes.

The re-emergence of stem rust on wheat in Europe and Africa is reinforcing the ongoing need for durable resistance gene deployment. Here, we isolate from wheat, Sr26 and Sr61, with both genes independently introduced as alien chromosome introgressions from tall wheat grass (Thinopyrum ponticum). Mutational genomics and targeted exome capture identify Sr26 and Sr61 as separate single genes that encode unrelated (34.8%) nucleotide binding site leucine rich repeat proteins. Sr26 and Sr61 are each validated by transgenic complementation using endogenous and/or heterologous promoter sequences. Sr61 orthologs are absent from current Thinopyrum elongatum and wheat pan genome sequences, contrasting with Sr26 where homologues are present. Using gene-specific markers, we validate the presence of both genes on a single recombinant alien segment developed in wheat. The co-location of these genes on a small non-recombinogenic segment simplifies their deployment as a gene stack and potentially enhances their resistance durability.

Niche specificity and functional diversity of the bacterial communities associated with Ginkgo biloba and Panax quinquefolius.

Plant-associated bacteria can establish mutualistic relationships with plants to support plant health. Plant tissues represent heterogeneous niches with distinct characteristics and may thus host distinct microbial populations. The objectives of this study are to investigate the bacterial communities associated with two medicinally and commercially important plant species; Ginkgo biloba and Panax quinquefolius using high Throughput Sequencing (HTS) of 16S rRNA gene, and to evaluate the extent of heterogeneity in bacterial communities associated with different plant niches. Alpha diversity showed that number of operational taxonomic units (OTUs) varied significantly by tissue type. Beta diversity revealed that the composition of bacterial communities varied between tissue types. In Ginkgo biloba and Panax quinquefolius, 13% and 49% of OTUs, respectively, were ubiquitous in leaf, stem and root. Proteobacteria, Bacteroidetes, Actinobacteria and Acidobacteria were the most abundant phyla in Ginkgo biloba while Proteobacteria, Bacteroidetes, Actinobacteria, Plantomycetes and Acidobacteria were the most abundant phyla in Panax quinquefolius. Functional prediction of these bacterial communities using MicrobiomeAnalyst revealed 5843 and 6251 KEGG orthologs in Ginkgo biloba and Panax quinquefolius, respectively. A number of these KEGG pathways were predicted at significantly different levels between tissues. These findings demonstrate the heterogeneity, niche specificity and functional diversity of plant-associated bacteria.

Diversity and antibacterial activity of fungal endophytes from Eucalyptus exserta.

BACKGROUND: Eucalyptus bacterial wilt caused by Ralstonia solanacearum is an important eucalyptus disease. Endophytic fungi, an important source of natural active substances, provide a new breakthrough for the control of plant diseases. RESULTS: In the present study, 80 endophytic fungal isolates were obtained from the healthy branches and fruits of Eucalyptus exserta. Fifteen distinct isolates (MK120854-MK120868) were selected for further taxonomic identification through morphological trait assessments and internal transcribed spacer (ITS) region-rRNA gene sequence analysis. Thirteen genera, namely, Phyllosticta, Penicillium, Eutypella, Purpureocillium, Talaromyces, Lophiostoma, Cladosporium, Pestalotiopsis, Chaetomium, Fusarium, Gongronella, Scedosporium and Pseudallescheria, were identified on the basis of their morphological characteristics. Members of the genus Phyllosticta were the primary isolates, with a colonization frequency (CF) of 27.5 %. Most of the fungal isolates displayed antibacterial activity. The crude extracts obtained from Lophiostoma sp. Eef-7, Pestalotiopsis sp. Eef-9 and Chaetomium sp. Eef-10 exhibited strong inhibition on the test bacteria, and Lophiostoma sp. Eef-7 was further cultured on a large scale. Three known compounds, scorpinone (1), 5-deoxybostrycoidin (2) and 4-methyl-5,6-dihydro-2 H-pyran-2-one (3), were isolated from the endophytic fungus Lophiostoma sp. Eef-7 associated with E. exserta. The structures of these compounds were elucidated by analysis of 1D and 2D NMR and HR-ESI-MS spectra and a comparison of their spectral data with published values. Compounds 1 and 2 showed weak antimicrobial activity against Ralstonia solanacearum. CONCLUSIONS: Endophytic fungi from Eucalyptus exserta may represent alternative sources of antimicrobial agents. Lophiostoma sp. Eef-7 can produce 2-azaanthraquinone derivatives and shows weak antibacterial activity against Ralstonia solanacearum.

Characterization of the microbial communities in wheat tissues and rhizosphere soil caused by dwarf bunt of wheat.

Dwarf bunt of wheat, which is caused by Tilletia controversa J.G. Kühn, is a soil-borne disease which may lead up to an 80% loss of yield together with degradation of the quality of the wheat flour by production of a fishy smell. In this study, high-throughput sequencing technology was employed to characterize the microbial composition of wheat tissues (roots, spikes, first stem under the ear, and stem base) and rhizosphere soil of wheat varieties that are resistant and susceptible to T. controversa. We observed that the soil fungal community abundance and diversity were higher in resistant varieties than in susceptible varieties in both inoculated and uninoculated wheat, and the abundances of Sordariomycetes and Mortierellomycetes increased in the resistant varieties infected with T. controversa, while the abundances of Dothideomycetes and Bacteroidia increased in the susceptible varieties. Regarding the bacteria present in wheat tissues, the abundances of Chloroflexi, Bacteroidetes, Gemmatimonadetes, Verrucomicrobia and Acidobacteria in the ear and the first stem under the ear were higher than those in other tissues. Our results indicated that the abundances of Sordariomycetes, Mortierellomycetes, Leotiomycetes, Chryseobacterium and Massilia were higher in T. controversa-infected resistant varieties than in their controls, that Dothideomycetes, Bacteroidia, Nocardioides and Pseudomonas showed higher abundances in T. controversa-infected susceptible varieties, and that Curtobacterium, Exiguobacterium, Planococcus, and Pantoea may have higher abundances in both T. controversa-infected susceptible and resistant varieties than in their own controls.

Lactobacillus plantarum and molasses alter dynamic chemical composition, microbial community, and aerobic stability of mixed (amaranth and rice straw) silage.

BACKGROUND: The objective was to determine how molasses and Lactobacillus plantarum affect chemical composition, fermentation quality, aerobic stability, and the microbial community of an ensiled mixture of amaranth (Amaranthus hypochondriaus, AF) and rice straw. Treatments were control (C, no addition), L. plantarum (L; 2 × 105 cfu g-1 fresh weight), molasses (M; 40 g kg-1 fresh matter), and their combination (LM). All treatments were ensiled for 1, 3, 5, 7, and 30 days. RESULTS: All additives improved fermentation quality with greater lactic acid (LA), acetic acid, and lower pH than C silage over the ensiling period. The LM silage combination optimized fermentability, manifested as greater LA contents and a more rapid pH reduction during the first 7 days of ensiling than L or M silages. After 30 days of ensiling, inoculant L. plantarum increased Lactobacillus abundance and reduced bacterial diversity and Enterobacteriaceae abundance compared with silage treated with molasses. Molasses addition reduced the relative concentration of structural carbohydrates (neutral and acid detergent fiber, and hemicellulose) after 30 days of ensiling. Finally, there was spoilage after 2 days and 4 days of aerobic exposure in C and LM silages respectively, whereas L silage had not spoiled after 4 days. CONCLUSIONS: Although the combination of L. plantarum and molasses further optimized fermentation characteristics, L silage had better aerobic stability. © 2021 Society of Chemical Industry.

Morpho-molecular identification and first report of Fusarium equiseti in causing chilli wilt from Kashmir (Northern Himalayas).

Chilli (Capsicum annuum L.) is one of the most significant vegetable and spice crop. Wilt caused by Fusarium Sp. has emerged as a serious problem in chilli production. Internal transcribed spacer (ITS) region is widely used as a DNA barcoding marker to characterize the diversity and composition of Fusarium communities. ITS regions are heavily used in both molecular methods and ecological studies of fungi, because of its high degree of interspecific variability, conserved primer sites and multiple copy nature in the genome. In the present study we focused on morphological and molecular characterization of pathogen causing chilli wilt. Chilli plants were collected from four districts of Kashmir valley of Himalayan region. Pathogens were isolated from infected root and stem of the plants. Isolated pathogens were subjected to DNA extraction and PCR amplification. The amplified product was sequenced and three different wilt causing fungal isolates were obtained which are reported in the current investigation. In addition to Fusarium oxysporum and Fusarium solani, a new fungal species was found in association with the chilli wilt in Kashmir valley viz., Fusarium equiseti that has never been reported before from this region. The studies were confirmed by pathogenicity test and re-confirmation by DNA barcoding.

Genetics of nodulation in Aeschynomene evenia uncovers mechanisms of the rhizobium-legume symbiosis.

Among legumes (Fabaceae) capable of nitrogen-fixing nodulation, several Aeschynomene spp. use a unique symbiotic process that is independent of Nod factors and infection threads. They are also distinctive in developing root and stem nodules with photosynthetic bradyrhizobia. Despite the significance of these symbiotic features, their understanding remains limited. To overcome such limitations, we conduct genetic studies of nodulation in Aeschynomene evenia, supported by the development of a genome sequence for A. evenia and transcriptomic resources for 10 additional Aeschynomene spp. Comparative analysis of symbiotic genes substantiates singular mechanisms in the early and late nodulation steps. A forward genetic screen also shows that AeCRK, coding a receptor-like kinase, and the symbiotic signaling genes AePOLLUX, AeCCamK, AeCYCLOPS, AeNSP2, and AeNIN are required to trigger both root and stem nodulation. This work demonstrates the utility of the A. evenia model and provides a cornerstone to unravel mechanisms underlying the rhizobium-legume symbiosis.

Characterization of histological changes at the tillering stage (Z21) in resistant and susceptible wheat plants infected by Tilletia controversa Kühn.

BACKGROUND: Dwarf bunt, which is caused by Tilletia controversa Kühn, is a soilborne and seedborne disease that occurs worldwide and can lead to 70% or even total losses of wheat crops. However, very little information is available about the histological changes that occur in dwarf bunt-resistant and dwarf bunt-susceptible wheat plants at the tillering stage (Z21). In this study, we used scanning electron microscopy and transmission electron microscopy to characterize the histological changes at this stage in resistant and susceptible wheat cultivars infected by T. controversa. RESULTS: Using scanning electron microscopy, the root, stem, and leaf structures of resistant and susceptible cultivars were examined after T. controversa infection. The root epidermal and vascular bundles were more severely damaged in the susceptible T. controversa-infected plants than in the resistant plants. The stem cell and longitudinal sections were much more extensively affected in susceptible plants than in resistant plants after pathogen infection. However, slightly deformed mesophyll cells were observed in the leaves of susceptible plants. With transmission electron microscopy, we found that the cortical bundle cells and the cell contents and nuclei in the roots were more severely affected in the susceptible plants than in the resistant plants; in the stems and leaves, the nuclei, chloroplasts, and mesophyll cells changed significantly in the susceptible plants after fungal infection. Moreover, we found that infected susceptible and resistant plants were affected much more severely at the tillering stage (Z21) than at the seedling growth stage (Z13). CONCLUSION: Histological changes in the wheat roots, stems and leaves were much more severe in T. controversa-infected susceptible plants than in infected resistant plants at the tillering stage (Z21).

Effect of a Bacillus subtilis strain on flax protection against Fusarium oxysporum and its impact on the root and stem cell walls.

In Normandy, flax is a plant of important economic interest because of its fibres. Fusarium oxysporum, a telluric fungus, is responsible for the major losses in crop yield and fibre quality. Several methods are currently used to limit the use of phytochemicals on crops. One of them is the use of plant growth promoting rhizobacteria (PGPR) occurring naturally in the rhizosphere. PGPR are known to act as local antagonists to soil-borne pathogens and to enhance plant resistance by eliciting the induced systemic resistance (ISR). In this study, we first investigated the cell wall modifications occurring in roots and stems after inoculation with the fungus in two flax varieties. First, we showed that both varieties displayed different cell wall organization and that rapid modifications occurred in roots and stems after inoculation. Then, we demonstrated the efficiency of a Bacillus subtilis strain to limit Fusarium wilt on both varieties with a better efficiency for one of them. Finally, thermo-gravimetry was used to highlight that B. subtilis induced modifications of the stem properties, supporting a reinforcement of the cell walls. Our findings suggest that the efficiency and the mode of action of the PGPR B. subtilis is likely to be flax variety dependent.

Genome-wide identification of the maize 2OGD superfamily genes and their response to Fusarium verticillioides and Fusarium graminearum.

In maize, eat rot and stalk rot caused by Fusarium verticillioides and Fusarium graminearum lead to contamination of moldy grains to produce mycotoxins. Identification of resistance genes against these pathogens for maize breeding is an effective way for disease control. Several 2-oxoglutarate-dependent dioxygenase (2OGD) proteins have been found to confer resistance to different pathogens in diverse plant species. However, little is known about the 2OGD superfamily in maize. Here, we identified 103 putative 2OGD genes in maize from a genome-wide analysis, and divided them into three classes - DOXA, DOXB, and DOXC. We further comprehensively investigated their gene structure, chromosome distribution, phylogenetic tree, gene-function enrichment, and expression profiles among different tissues. The genes encoding three 2OGD proteins, ACO, F3H, and NCS involved in ethylene biosynthesis, flavonoids biosynthesis, and alkaloids biosynthesis pathways, respectively, were identified to be induced by F. verticillioides and F. graminearum. The promoters of the three genes contain the binding sites for the transcription factor ZmDOF and ZmHSF, which are also induced by the two pathogens. The results imply that the three 2OGDs and the two transcription factors might be involved in the resistance to the two pathogens. This study provided a comprehensive understanding of the 2OGD superfamily in maize and laid the foundation for the further functional analysis of their roles in maize resistance to eat rot and stalk rot.

Identification of native endophytic Trichoderma spp. for investigation of in vitro antagonism towards Armillaria mellea using synthetic- and plant-based substrates.

AIMS: To isolate endophytic Trichoderma species and investigate the potential for biological control of the root rot pathogen Armillaria mellea. METHODS AND RESULTS: In all, 40 Trichoderma isolates were obtained from a range of host plants and identities were confirmed by ITS, rpb2 and tef1 sequence. When tested in dual culture assays for antagonism against A. mellea, Trichoderma isolates overgrew the A. mellea colonies within four days and by eight days 38 Trichoderma isolates significantly reduced A. mellea colony size. Armillaria mellea was unable to be recovered from five of eight co-cultivations tested, suggesting Trichoderma had killed the A. mellea in these cases. Pre-colonized hazel disks were used to determine what happens in a more heterogeneous situation with A. mellea and a refined set of eight Trichoderma isolates. Similar to plate-based assays, Trichoderma quickly covered A. mellea stopping any further growth and two Trichoderma isolates were able to eradicate A. mellea. CONCLUSIONS: Of the Trichoderma spp. tested, endophytic isolates of Trichoderma virens and T. hamatum offered the greatest antagonism towards A. mellea. Using pre-colonized hazel disks was of great importance for this work to demonstrate the fungal interactions in plant material. SIGNIFICANCE AND IMPACT OF THE STUDY: Controlling Armillaria root rot is difficult with chemical treatments, thus an environmentally benign and cost-effective alternative is required. This study highlights the prospect of biological control as an effective, environmentally friendly alternative to chemicals.

Production of phenolic compounds and antioxidant activity via bioconversion of wheat straw by Inonotus obliquus under submerged fermentation with the aid of a surfactant.

BACKGROUND: This study investigated the effect of surfactants on wheat straw biodegradation and the growth-associated generation of exo- and endo-phenolic compounds (EPC and IPC) and antioxidant activity expression by liquid-cultured Inonotus obliquus, an edible and medicinal mushroom, also known as a white rot fungus. Changes in the chemical composition and multiscale structure of wheat straw, in the production and activity of EPC and IPC and in individual flavonoids were analyzed. RESULTS: Fungal pretreatment decreased significantly the contents of all lignocellulose components, increased and enlarged substrate porosity and caused changes in the structure of wheat straw with the aid of Triton X-100. A gradual increase in EPC and IPC production was observed up to 6.4- and 1.5-fold for 9 days. The EPC obtained on day 9 showed the highest antioxidant activity (IC50 of 30.96 mg L-1 ) against 2,2-diphenyl-1-picrylhydrazyl radicals. High-performance liquid chromatographic results indicated the presence of high amounts of epicatechin-3-gallate (ECG; (374.9 mg g-1 ) and epigallocatechin-3-gallate (EGCG; 447.2 mg g-1 ) in the EPC; other polyphenols were also enhanced but to a lesser extent. Surfactant supplementation was effective in enhancing flavonoid production and in increasing antioxidant activity in EPC. CONCLUSIONS: The results indicated enhanced accumulation of phenolic compounds, particularly ECG and EGCG in Inonotus obliquus via biodegradation and bioconversion of lignocellulose residues. They also indicated enhancement in the production of several flavonoids and also an increase in antioxidant activity in the product by a surfactant-treated process, which may be a useful way of exploiting underused lignocellulosic residues to various high-added-value functional ingredients. © 2020 Society of Chemical Industry.