Search Results (18)

Atriplex hortensis var. rubra (red orache, RO) is a halotolerant species rich in nutraceutical compounds, which makes it a valuable crop for human nutrition. This plant could also be exploited for phytoremediation of contaminated soil and wastewater, and for saline aquaponics. A root rot disease was observed on hydroponically grown RO plants, caused by Pythium deliense and Pythium Cluster B2a sp. Identification was based on morphology, molecular analysis (ITS and COI), and phylogenetic analysis. We assessed disease severity in plants grown in a growth chamber with nutrient solutions containing different NaCl concentrations (0, 7, and 14 g L⁻¹ NaCl). In vitro growth at different salinity levels and temperatures was also evaluated. Both Pythium species were pathogenic but showed different responses. Pythium deliense was significantly more virulent than Pythium Cluster B2a sp., causing a steady reduction in root dry weight (RDW) of 70% across all salinity levels. Pythium Cluster B2a sp. reduced RDW by 50% at 0 and 7 g L⁻¹ NaCl while no symptoms were observed at 14 g L⁻¹ NaCl. Pythium deliense grew best at 7 and 14 g L⁻¹ NaCl, while Pythium Cluster B2a sp. growth was reduced at 14 g L⁻¹ NaCl. Both pathogens had an optimum temperature of 30 °C. This is the first report of Pythium spp. causing root rot on RO grown hydroponically. The effective use of halophytic crops must consider pathogen occurrence and fitness in saline conditions. Full article

Burkholderia gladioli is a multifaceted bacterium with both pathogenic and beneficial strains, and nonpathogenic Burkholderia species have shown potential as plant growth-promoting rhizobacteria (PGPRs) and biocontrol agents. However, the molecular mechanisms underlying their beneficial functions remain poorly characterized. This study systematically investigated the antimicrobial mechanisms and plant growth-promoting properties of B. gladioli strain ZBSF BH07, isolated from the grape rhizosphere, by combining genomic and functional analyses, including whole-genome sequencing, gene annotation, phylogenetic and comparative genomics, in vitro antifungal assays, and plant growth promotion evaluations. The results showed that ZBSF BH07 exhibited broad-spectrum antifungal activity, inhibiting 14 grape pathogens with an average inhibition rate of 56.58% and showing dual preventive/curative effects against grape white rot, while also significantly promoting grape seedling growth with increases of 54.9% in plant height, 172.9% in root fresh weight, and 231.34% in root dry weight. Genomic analysis revealed an 8.56-Mb genome (two chromosomes and one plasmid) encoding 7431 genes and 26 secondary metabolite biosynthesis clusters (predominantly nonribosomal peptide synthetases), supporting its capacity for antifungal metabolite secretion, and functional analysis confirmed genes for indole-3-acetic acid (IAA) synthesis, phosphate solubilization, and siderophore production. These results demonstrate that ZBSF BH07 suppresses pathogens via antifungal metabolites and enhances grape growth through phytohormone regulation and nutrient acquisition, providing novel insights into the dual mechanisms of B. gladioli as a biocontrol and growth-promoting agent and laying a scientific foundation for developing sustainable grapevine disease management strategies. Full article

The citrus industry contributes to the cultivation of one of the most important fruit crops globally. However, citrus trees are susceptible to numerous Bisifusarium, Fusarium, and Neocosmospora-linked diseases, with dry root rot posing a serious threat to citrus orchards worldwide. These infections are exacerbated by biotic and abiotic stresses, leading to increased disease incidence. Healthy trees unexpectedly wilt and fall, exhibiting symptoms such as chlorosis, dieback, necrotic roots, root rot, wood discolouration, and eventual decline. Research indicates that the disease is caused by a complex of species from the Nectriaceae family, with Neocosmospora solani being the most prominent. To improve treatment and management strategies, further studies are needed to definitively identify these phytopathogens and understand the conditions and factors associated with Bisifusarium, Fusarium, and Neocosmospora-related diseases in citrus. This review focuses on the epidemiology and symptomatology of Fusarium and Neocosmospora species, recent advances in molecular techniques for accurate phytopathogen identification, and the molecular mechanisms of pathogenicity and resistance underlying Fusarium and Neocosmospora–citrus interactions. Additionally, the review highlights novel alternative methods, including biological control agents, for disease control to promote environmentally friendly and sustainable agricultural practices. Full article

Black root rot is a dangerous disease affecting many crops. It is caused by pathogens formerly known as Thielaviopsis basicola and then reclassified as two cryptic species, Berkeleyomyces basicola and B. rouxiae. The aim of this study was to perform species identification, morphological characterization, and pathogenicity tests for fungal isolates obtained from tobacco roots with black root rot symptoms in Poland. DNA sequences of the three regions (ITS, ACT, MCM7) were highly similar to the sequences of B. rouxiae deposited in the NCBI database. Phylogenetic analysis confirmed the assignment of the obtained isolates to this species. The cultures of four representative isolates (namely OT2, OT3, WPT7, WPT8) showed a similar structure and gray/brown color of the mycelium, although their growth rate varied from 3.8 to 5.1 mm/day depending on the isolate. The sizes of the endoconidia and chlamydospores showed a considerable variation, although they fit within ranges previously described for B. rouxiae. Pathogenicity tests performed on young tobacco plants grown in the inoculated peat substrate revealed differences among the four isolates. WPT7 demonstrated the lowest level of aggressiveness for tobacco. In contrast, the remaining three isolates caused severe disease symptoms and significantly reduced shoot and root dry weights of the susceptible cultivar Virginia Joyner. A parallel pathogenicity test performed on cultivar VRG 10TL confirmed the effectiveness of black root rot resistance derived from Nicotiana debneyi. Full article

Zinc oxide nanoparticles (ZnO NPs) exhibit diverse applications, including antimicrobial, UV-blocking, and catalytic properties, due to their unique structure and properties. This study focused on the characterization of zinc oxide nanoparticles (ZnO NPs) synthesized from Juglans regia leaves and their application in mitigating the impact of simultaneous infection by Meloidogyne arenaria (root-knot nematode) and Macrophomina phaseolina (root-rot fungus) in cowpea plants. The characterization of ZnO NPs was carried out through various analytical techniques, including UV–visible spectrophotometry, Powder-XRD analysis, FT-IR spectroscopy, and SEM-EDX analysis. The study confirmed the successful synthesis of ZnO NPs with a hexagonal wurtzite structure and exceptional purity. Under in vitro conditions, ZnO NPs exhibited significant nematicidal and antifungal activities. The mortality of M. arenaria juveniles increased with rising ZnO NP concentrations, and a similar trend was observed in the inhibition of M. phaseolina mycelial growth. SEM studies revealed physical damage to nematodes and structural distortions in fungal hyphae due to ZnO NP treatment. In infected cowpea plants, ZnO NPs significantly improved plant growth parameters, including plant length, fresh mass, and dry mass, especially at higher concentrations. Leghemoglobin content and the number of root nodules also increased after ZnO NP treatment. Additionally, ZnO NPs reduced gall formation and egg mass production by M. arenaria nematodes and effectively inhibited the growth of M. phaseolina in the roots. Furthermore, histochemical analyses demonstrated a reduction in oxidative stress, as indicated by decreased levels of reactive oxygen species (ROS) and lipid peroxidation in ZnO NP-treated plants. These findings highlight the potential of green-synthesized ZnO NPs as an eco-friendly and effective solution to manage disease complex in cowpea caused by simultaneous nematode and fungal infections. Full article

Root rot disease poses a significant threat to canola (Brassica napus), underscoring the need for a comprehensive understanding of its causal agents for more effective disease mitigation. The composition and diversity of fungal pathogens associated with root rot of canola in Alberta, Canada, were evaluated from plant tissue samples collected in 2021 and 2022. The study revealed Fusarium spp. as the predominant pathogens found in almost all surveyed fields. Fusarium avenaceum, F. redolens, and F. solani were among the most frequently recovered species. Greenhouse trials confirmed their pathogenicity, with F. avenaceum and F. sporotrichioides found to be particularly aggressive. Additionally, F. sporotrichioides and F. commune were identified for the first time as canola root rot pathogens. Inoculation with isolates of most species resulted in significant reductions in seedling emergence, plant height, and shoot and root dry weights. Analysis of translation elongation factor 1-α (TEF-1α) and internal transcribed spacer (ITS) sequences confirmed the identity of the Fusarium spp., while concatenating the ITS and TEF-1α sequences enabled improved species differentiation. Geographic and year effects did not influence fungal diversity or aggressiveness, as determined by principal component analysis. This study emphasized the high diversity and impact of Fusarium spp. in causing canola root rot. Full article

Fusarium proliferatum is associated with the root rot of many plant species, but knowledge of its impact on western Canadian field crops is limited. This study assessed the host range of this fungus and its effect on plant emergence, plant height, and shoot and root dry weights in repeated greenhouse experiments with wheat, barley, faba beans, peas, lentils, canola, lupine, and soybeans. Infection was confirmed via PCR, and principal component analysis determined the utility of different parameters in assessing host responses. All crops were at least partly susceptible, developing mild to severe disease at the seedling and adult stages, and showing significant reductions in growth. In general, the barley and wheat demonstrated higher tolerances to infection, followed by the faba bean and the pea. The soybean, canola, lupine, and lentil were most susceptible. The canola and the soybean were particularly vulnerable to F. proliferatum at the pre-emergence stage, while infection greatly reduced the lentil’s biomass. Reductions in the barley’s emergence and other growth parameters, however, occurred only under a high inoculum concentration. Variability in root rot severity among cultivars of the same crop indicated some diversity in host reactions within species. Nonetheless, the absence of fully-resistant crops may pose challenges in managing F. proliferatum in western Canadian cropping systems. Full article

Peanut root rot, caused by Fusarium spp., is a devastating fungal disease. As part of a program to obtain a biocontrol agent to control peanut root rot in the field, a bacterial strain LY-1 capable of inhibiting the growth of the fungus in vitro was isolated from rhizosphere soil samples collected from wild mint by agar disk dilution and dual-culture assay. Strain LY-1 was identified as Bacillus subtilis based on morphological characteristics, 16S rDNA, and gyrA sequence analyses. The bacterial suspension and cell-free culture filtrate of LY-1 could significantly inhibit the growth of Fusarium oxysporum, Fusarium proliferatum and Fusarium solani, but volatile organic compounds from the cultures had only a weak effect on mycelial growth. The percentage inhibition of 20% concentration of the cell-free culture filtrate of LY-1 on conidium production of each of the three Fusarium species was greater than 72.38%, and the percentage inhibition by the culture filtration on the germination of conidia of the three species was at least 62.37%. The production of extracellular enzyme activity by LY-1 was studied in functional assays, showing protease, cellulase, amylase, chitinase, and β-1,3-glucanase activity, while LY-1 contained a gene encoding iturin, an antifungal lipopeptide. In addition, under pot culture in a greenhouse, culture filtrate of LY-1 significantly promoted the growth of peanut, increasing the fresh and dry mass of the plant by 30.77% and 27.27%, respectively, in comparison with the no-filtrate control. The culture filtrate of LY-1 increased the resistance of peanut plants to F. oxysporum, with the biocontrol efficiency reaching 44.71%. In conclusion, B. subtilis LY-1, a plant-growth-promoting rhizobacterium, was able to protect peanuts from Fusarium spp. infection. Full article

Cigar tobacco, an economically important cash crop, holds a substantial role within the fiscal framework of the national economy. This crop, however, is characterized by a marked vulnerability to pathogenic bacteria, culminating in consequential financial loss throughout its cultivation phase. Plant growth-promoting rhizobacteria (PGPR), a salient class of advantageous bacterial flora, are recognized for their ability to enhance plant growth, inhibit deleterious pathogens, and synthesize compounds that either have a direct impact on plant morphogenesis or activate otherwise ineffectual soil components. Through these mechanisms, PGPR augments the soil’s nutritional profile, making it more receptive to plant uptake, thus stimulating vegetative growth. The Bacillus subtilis microbial fertilizer, the prime exemplar of PGPR, demonstrates not only a pathogen-suppressive effect but also an induction of the plant’s innate disease resistance mechanism. This bolsters the plant’s resilience to disease fosters a probiotic milieu within the soil, and catalyzes the formation of agglomerate structures, all of which contribute to enhanced soil fertility and moisture retention, increased soil friability, and the facilitation of root expansion. In this study, a controlled pot experiment was conducted to elucidate the mechanism through which inter-root probiotics rehabilitate the soil’s ecosystem and foster crop growth in cigar tobacco seedlings afflicted with root black rot bacteria. Four treatments were instituted, including CK: a blank control (no microbial application); A: probiotic only (Bacillus subtilis microbial fertilizer); B: both pathogenic and probiotic (the Bacillus subtilis microbial fertilizer together with root black rot pathogen); C: pathogenic only (the root black rot pathogen). Our empirical findings delineate that the presence of pathogenic bacteria deteriorates the soil environment, thereby constraining the transmutation of soil nutrients and their subsequent assimilation by plants. This severely impedes the vegetative development of cigar plants. By contrast, the application of a PGPR microbial fertilizer modified the soil microbial community structure, exhibiting an antagonistic interaction with the indigenous pathogenic bacterial species. Relative to the CK treatment, the application of the Bacillus subtilis microbial fertilizer was found to invigorate the catalytic conversion of soil enzymes, incrementing the peroxidase, acid phosphatase, urease, and sucrase activity by 12.98%, 19.55%, 13.57%, and 17.91%, respectively. Meanwhile, it was observed to ameliorate the soil’s physicochemical attributes, enhancing the available content of nitrogen, phosphorus, and potassium by 4.52%, 6.52%, and 15.14%, respectively, along with the augmentation of soil organic matter content by 17.33%. The fortification of soil physicochemical properties and the enrichment of soil fertility, as a result of the PGPR microbial fertilizer application, translated into a robust 57.23% enhancement of root vigor and a 60.47% extension of the root length of cigar tobacco seedlings. These soil amendments subsequently fueled an uptick in the growth parameters of cigar plants, including increases in plant height, stem girth, leaf count, maximal leaf dimensions, and both the fresh and dry weight of cigar tobacco. Full article

Rhizoctonia solani causes severe diseases in many plant species, particularly root rot in tomato plants. For the first time, Trichoderma pubescens effectively controls R. solani in vitro and in vivo. R. solani strain R11 was identified using the ITS region (OP456527); meanwhile, T. pubescens strain Tp21 was characterized by the ITS region (OP456528) and two genes (tef-1 and rpb2). The antagonistic dual culture method revealed that T. pubescens had a high activity of 76.93% in vitro. A substantial increase in root length, plant height, shoot fresh and dry, and root fresh and dry weight was indicated after applying T. pubescens to tomato plants in vivo. Additionally, it significantly increased the chlorophyll content and total phenolic compounds. The treatment with T. pubescens exhibited a low disease index (DI, 16.00%) without significant differences with Uniform^® fungicide at a concentration of 1 ppm (14.67%), while the R. solani-infected plants showed a DI of 78.67%. At 15 days after inoculation, promising increases in the relative expression levels of three defense-related genes (PAL, CHS, and HQT) were observed in all T. pubescens treated plants compared with the non-treated plants. Plants treated with T. pubescens alone showed the highest expression value, with relative transcriptional levels of PAL, CHS, and HQT that were 2.72-, 4.44-, and 3.72-fold higher in comparison with control plants, respectively. The two treatments of T. pubescens exhibited increasing antioxidant enzyme production (POX, SOD, PPO, and CAT), while high MDA and H₂O₂ levels were observed in the infected plants. The HPLC results of the leaf extract showed a fluctuation in polyphenolic compound content. T. pubescens application alone or for treating plant pathogen infection showed elevated phenolic acids such as chlorogenic and coumaric acids. Therefore, the ability of T. pubescens to inhibit the growth of R. solani, enhance the development of tomato plants, and induce systemic resistance supports the application of T. pubescens as a potential bioagent for managing root rot disease and productivity increase of crops. Full article

Fusarium dry rot (FDR) is a postharvest disease of garlic crops causing yield losses worldwide. Fusarium proliferatum has been identified as the main species causing the disease. Symptoms begin as small brown lesions with a dehydrated appearance that can progress to cover the entire clove during the storage period. Symptoms on growing plants cause brown lesions on the basal plates and roots, and sometimes damping-off is observed. F. proliferatum is a polyphagous pathogen with a wide range of hosts. This pathogen colonizes garlic roots, remaining as a latent pathogen, and develops rot during storage. The pathogen can overwinter in the soil, infested crop residues, and weeds. The fungus can also persist on garlic cloves, acting as primary inoculum in the field and contributing to the long-distance spread. Using healthy plant material, rotating crops, burying crop residues, avoiding bulb injury during harvest and subsequent handling, and providing appropriate postharvest environmental conditions are crucial factors that greatly influence the disease severity. Choosing a suitable non-host crop to achieve truly effective rotation is sometimes difficult. Chemical control in the form of seed treatments or field spraying of the crop has a limited effect on controlling FDR. Field applications of biological control agents have shown some efficacy, but conditions to optimize their activity must be determined. Moreover, different soil management strategies to reduce soil inoculum must be also studied. Full article

Infections by Fusarium and Fusarium-like species on cacti and other succulent plants cause the syndrome known as Fusarium dry rot and soft rot. There are only few records of Fusarium species as pathogens of cacti and other succulent plants from Iran. The objective of this study was the identification and characterization of fusarioid species recovered from ornamental succulents in Shiraz County, Iran. Three fusarioid species, including F. oxysporum, F. proliferatum, and Neocosmospora falciformis (formerly F. falciforme), were recovered from 29 diverse species of cacti and other succulents with symptoms of Fusarium dry rot and soft rot. The three fungal species were identified on the basis of morphological characters and the phylogenetic analysis of the translation elongation factor1-α (tef1) nuclear gene. The F. oxysporum isolates were identified as F. oxysporum f. sp. opuntiarum. The pathogenicity of the three fusarioid species was tested on a range of economically important ornamental succulents, mostly in the Cactaceae family. The three species showed a broad host spectrum and induced different types of symptoms on inoculated plants, including soft and dry rot, chlorosis, necrotic spots, wilt, drying, root and crown rot. This is the first report of N. falciformis as a pathogen of succulent plants worldwide. Full article

From 2018 to 2020, surveys of oomycetes associated with root and crown rot of almond (Prunus dulcis) were conducted on diseased young almond trees in commercial orchards and nurseries in six provinces of Spain. A total of 104 oomycete isolates were obtained from plant and soil samples, which h were identified by sequencing the internal transcribed spacer (ITS) region of the ribosomal DNA. Diverse species belonging to the genera Globisporangium, Phytophthora, Phytopythium and Pythium were found, Phytopythium vexans and Phytophthora niederhauserii being the most frequent. The pathogenicity of these two species to one-year-old almond seedlings of ‘Garnem’ (P. dulcis × P. persica) rootstock was studied. All seedlings inoculated with Pp. vexans and Ph. niederhauserii isolates showed severe symptoms at the late stage of the pathogenicity test (defoliation, wilting and dieback) and several plants died. Some isolates of Ph. niederhauserii significantly reduced the dry weight of the roots compared with the control, but this effect was not observed in seedlings inoculated with Pp. vexans. These results provide new information about the oomycete species present in almond crops in Spain and highlight the importance of carrying out frequent phytosanitary surveys for a better knowledge of potential risks posed by these soil-borne pathogens. Full article

Dry root rot (Rhizoctonia bataticola) is an important disease of lentils (Lens culinaris Medik.).To gain an insight into the molecular aspects of host-pathogen interactions, the RNA-seq approach was used in lentils following inoculation with R.bataticola. The RNA-Seq has generated >450 million high-quality reads (HQRs) and nearly 96.97% were properly aligned to the reference genome. Very high similarity in FPKM (fragments per kilobase of exon per million mapped fragments) values (R > 0.9) among biological replicates showed the consistency of the RNA-Seq results. The study revealed various DEGs (differentially expressed genes) that were associated with changes in phenolic compounds, transcription factors (TFs), antioxidants, receptor kinases, hormone signals which corresponded to the cell wall modification enzymes, defense-related metabolites, and jasmonic acid (JA)/ethylene (ET) pathways. Gene ontology (GO) categorization also showed similar kinds of significantly enriched similar GO terms. Interestingly, of the total unigenes (42,606), 12,648 got assembled and showed significant hit with Rhizoctonia species. String analysis also revealed the role of various disease responsive proteins viz., LRR family proteins, LRR-RLKs, protein kinases, etc. in the host-pathogen interaction. Insilico validation analysis was performed using Genevestigator^® and DEGs belonging to six major defense-response groups viz., defense-related enzymes, disease responsive genes, hormones, kinases, PR (pathogenesis related) proteins, and TFs were validated. For the first time some key miRNA targets viz. miR156, miR159, miR167, miR169, and miR482 were identified from the studied transcriptome, which may have some vital role in Rhizoctonia-based responses in lentils. The study has revealed the molecular mechanisms of the lentil/R.bataticola interactions and also provided a theoretical approach for the development of lentil genotypes resistant to R.bataticola. Full article

Sweet potato is the 11th most important food crop in the world and an excellent source of nutrition. Postharvest diseases were monitored in sweet potato storage roots collected from the local markets in Korea during 2021. Several diseases including Fusarium surface and root rot, charcoal rot, dry rot, and soft rot were observed in the postharvest sweet potatoes. A total of 68 fungal isolates were obtained from the diseased samples, and the isolates were grouped into 8 different fungal colony types. Based on multilocus phylogeny and morphological analysis of 17 representative isolates, the isolates were identified as Fusarium oxysporum, F. ipomoeae, F. solani, Penicillium citrinum, P. rotoruae, Aspergillus wentii, Mucor variicolumellatus (Mu. circinelloides species complex), and Macrophomina phaseolina. F. oxysporum was the predominant pathogen as this is the most common pathogen of sweet potato storage roots causing the surface rot disease, and M. phaseolina caused the most severe disease among the pathogens. Dual culture antagonistic assays were evaluated using Trichoderma harzianum strains CMML20–26 and CMML20–27. The results revealed that the two strains showed strong antifungal activity in different ranges against all tested pathogens. This study provides an understanding of diverse postharvest diseases in sweet potatoes and suggests potential biocontrol agents to manage the diseases. In addition, this is the first report of sweet potato storage root rot diseases caused by A. wentii, and P. rotoruae worldwide. Full article