Search Results (10)

Synthetic chemicals, such as fertilizers and pesticides, are widely used in agriculture to improve soil fertility and to control weeds, pests and diseases. Numerous studies have highlighted the negative effects of these chemicals on the soil environment. In contrast, during vermicomposting, earthworms generate numerous beneficial outcomes. This study aimed to screen antagonistic bacteria found after vermicomposting for their potential to inhibit the pre-emergence damping-off of tomato seedlings caused by Rhizoctonia solani. Using a dual culture method, 85 bacterial isolates were screened, three of which demonstrated antagonistic activity against R. solani. Molecular characterization based on 16S ribosomal RNA identified the bacterial isolates as Bacillus subtilis (NOAC.B77), Bacillus vallismortis (NOAC.B42), and Bacillus cereus (NOAC.B17). The strains NOAC.B77 and NOAC.B42 exhibited the most significant inhibitory effects on the mycelial growth of R. solani, with inhibition levels of 80.8% and 79.2%, respectively. In greenhouse trials, only 13% of the Inoculated, Unprotected Control tomato seedlings emerged, i.e., the R. solani inoculum caused an 87% level of preemergence damping off. In contrast, after treatment with the bacterial strains NOAC.B77 and NOAC.B42, tomato seedling emergence was not significantly different from the Uninoculated Control. These results suggest that the bacterial strains NOAC.B77 and NOAC.B42 could be commercialized as biological agents to control damping-off of tomato seedlings under greenhouse conditions. Full article

The biosynthesis of silver nanoparticles (AgNPs) using plant extracts has become a safe replacement for conventional chemical synthesis methods to fight plant pathogens. In this study, the antifungal activity of biosynthesized AgNPs was evaluated both in vitro and under greenhouse conditions against root rot fungi of common beans (Phaseolus vulgaris L.), including Macrophomina phaseolina, Pythium graminicola, Rhizoctonia solani, and Sclerotium rolfsii. Among the eleven biosynthesized AgNPs, those synthesized using Alhagi graecorum plant extract displayed the highest efficacy in suppressing those fungi. The findings showed that using AgNPs made with A. graecorum at a concentration of 100 μg/mL greatly slowed down the growth of mycelium for R. solani, P. graminicola, S. rolfsii, and M. phaseolina by 92.60%, 94.44%, 75.93%, and 79.63%, respectively. Additionally, the minimum inhibitory concentration (75 μg/mL) of AgNPs synthesized by A. graecorum was very effective against all of these fungi, lowering the pre-emergence damping-off, post-emergence damping-off, and disease percent and severity in vitro and greenhouse conditions. Additionally, the treatment with AgNPs led to increased root length, shoot length, fresh weight, dry weight, and vigor index of bean seedlings compared to the control group. The synthesis of nanoparticles using A. graecorum was confirmed using various physicochemical techniques, including UV spectroscopy, Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) analysis. Collectively, the findings of this study highlight the potential of AgNPs as an effective and environmentally sustainable approach for controlling root rot fungi in beans. Full article

The in vitro and in vivo efficacy of three biocontrol agents, Trichoderma viride, Pseudomonas fluorescence, and Bacillus subtilis, were tested against Rhizoctonia solani (AG-4) infection compared to two conventional fungicides (Rizolex-T 50%wettable powder and Amistar 25%). Antifungal enzyme activity was assayed in the culture filtrate of the biocontrol agents. The impact of the tested biocontrol agents on the induction of the coriander immune system was investigated against R. solani by assessing the resistance-related enzymes and compounds in biocontrol agent-treated plants compared with the control. The obtained results revealed that all tested biocontrol agents significantly reduced the linear growth of R. solani, and T. viride recorded the highest inhibition percentage. This could be linked to the ability of T. viride to produce higher activities of antimicrobial enzymes, i.e., cellulase, chitinase, and protease, compared to P. fluorescence and B. subtilis. Applying the tested biocontrol agents significantly alleviated pre- and post-emergence damping-off and root rot/wilt diseases of infected coriander compared with untreated plants. The tested biocontrol agents exhibited significantly higher germination percentage and vigor index of the coriander than the tested fungicides. The tested biocontrol agents significantly minimized the reduction of photosynthetic pigments induced by R. solani. In addition, the results showed a significant increase in enzymes/molecules (i.e., phenylalanine, catalase, peroxidase, catalase, superoxide dismutase, phenylalanine ammonia-lyase, phenolics, ascorbic acids, and salicylic acid) involved directly and indirectly in coriander resistance to R. solani. The principal component analysis of the recorded data recommended the role of the high accumulation of oxidative parameters (hydrogen peroxide and lipid peroxidation) and the inhibition of phenolic compounds in the downregulation of coriander resistance against R. solani. The heatmap analysis results revealed that biocontrol agents, especially Trichoderma, enhanced the resistance against R. solani via the stimulation of salicylic acid, phenolics, and antioxidant enzymes. Overall, the data recommended the efficacy of biocontrol agents, especially T. viride, against R. solani infecting coriander plants, which could be an efficient and a safer alternative to conventional fungicides. Full article

Agricultural crops are facing a continuous threat due to biotic and abiotic stresses, thus, limiting the crop productivity, and thereby, threatening food security. Plant roots attract several kinds of microbes that induce resistance in plants against these stresses by enhancing the activity of the antioxidant enzymes, phenolic and other non-phenolic compounds, and thereby, have a beneficial effect on plants. Vast research has been carried out on biocontrol agents to manage soil-borne plant pathogens, but there has been limited success in the development of region-specific, commercially viable microbial inoculants. The present research was framed with a view to screen and evaluate native Pseudomonads from the rhizosphere of different crops in lateritic soils and their exploitation in biotic and abiotic stress management under the red and lateritic zone of West Bengal. In the lateritic area of West Bengal, the lowest pH as well as the highest culturable rhizobacterial population was found in the soil of Bankura. Among all the isolated rhizobacteria, 43.33% were found to be moderately antagonistic against three different soil-borne plant pathogens viz., Rhizoctonia solani, Sclerotinia sclerotiorum and Sclerotium rolfsii—while only 6.67% were found to be very highly antagonistic against these soil-borne plant pathogens. Augmented seeds of tomato, cowpea and French bean with native rhizobacteria enhanced the vigour index and 16.67% of the isolates were found to have a high value of vigour index in the normal and acid stress conditions. Based on acid tolerance, antagonistic activity and the seed vigour assay, a total of 13 isolates from 97 of lateritic area were selected. Out of the 13 selected isolates, 7 were positive for protease and lipase production, 8 isolates were positive for the production of HCN, siderophore and salicylic acid production and 9 isolates were found to be positive for IAA, phosphate solubilisation, amylase and chitinase production. Species of beneficial Pseudomonads such as Pseudomonas aeruginosa, P. fluorescens, P. Plecoglossicida, P. helmanticensis, P. geniculate, P. baetica and P. putida were found. Five isolates were used to study the effect on plant growth in terms of germination (%), root and shoot length, as well as fresh root and shoot weight and disease patterns in terms of pre- and post-emergence damping-off under the semi-field condition. Full article

The phytopathogenic basidiomycetous fungus, Rhizoctonia solani, has a wide range of host plants including members of the family Poaceae, causing damping-off and root rot diseases. In this study, we biosynthesized spherical-shaped silicon dioxide nanoparticles (SiO₂ NPs; sized between 9.92 and 19.8 nm) using saffron extract and introduced them as a potential alternative therapeutic solution to protect wheat seedlings against R. solani. SiO₂ NPs showed strong dose-dependent fungistatic activity on R. solani, and significantly reduced mycelial radial growth (up to 100% growth reduction), mycelium fresh and dry weight, and pre-, post-emergence damping-off, and root rot severities. Moreover, the impact of SiO₂ NPs on the growth of wheat seedlings and their potential mechanism (s) for disease suppression was deciphered. SiO₂ NPs application also improved the germination, vegetative growth, and vigor indexes of infected wheat seedlings which indicates no phytotoxicity on treated wheat seedlings. Moreover, SiO₂ NPs enhanced the content of the photosynthetic pigments (chlorophylls and carotenoids), induced the accumulation of defense-related compounds (particularly salicylic acid), and alleviated the oxidative stress via stimulation of both enzymatic (POD, SOD, APX, CAT, and PPO) and non-enzymatic (phenolics and flavonoids) antioxidant defense machinery. Collectively, our findings demonstrated the potential therapeutic role of SiO₂ NPs against R. solani infection via the simultaneous activation of a multilayered defense system to suppress the pathogen, neutralize the destructive effect of ROS, lipid peroxidation, and methylglyoxal, and maintain their homeostasis within R. solani-infected plants. Full article

Combating soil pathogens that disable plant emergence is among the most difficult challenges of global agriculture. Legumes, preferred in sustainable cultivation systems, are particularly sensitive to pre-emergence damping-off of seedlings. Seed dressing is therefore a very important element in the cultivation technology. The aim of this study was to compare the impact of biological (Pythium oligandrum) and chemical (carboxin + thiuram) seed dressing on the quantitative and qualitative composition of microorganisms participating in the epidemiology of this disease, under specific hydrothermal conditions and chemical properties of the soil (pH, humus, macro-, and micronutrient). Microorganism identification was done using the MALDI-TOF MS (Matrix Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry) technique. Species were assigned to frequency groups, and populations of pathogens, saprophytes, and antagonists were identified. The biodiversity of these communities was expressed with Simpson’s Reciprocal, Shannon–Wiener, and Evenness (Shannon) indices. In individual variants of seed pre-treatment, the correlations between individual edaphic factors and the suppression of pre-emergence damping-off, the number of isolates obtained from infected seedlings, and the share of individual trophic groups of fungi were assessed. The main causes of pre-emergence damping-off of broad bean seedlings are Ilyonectria destructans, Globisporangium irregulare, Fusarium equiseti, Rhizoctonia solani, and Fusarium solani. Eliminating seed treatment results in a seedling mortality rate of 33.5–42.5%. The effectiveness of the chemical protection product is 44.2% and 25.9%. Carboxin and thiuram reduce the diversity of microorganisms involved in the pathogenesis of pre-emergence damping-off and limit the presence of antagonistic fungi. Under the influence of P. oligandrum, there was a five-fold increase in the population of antagonists. An increase in humus in the soil reduces the percentage of diseased broad bean seedlings. Full article

During a survey of oomycetes in ornamental plants carried out at the University of Aberdeen in 2014–2015, Pythium kashmirense was isolated from a specimen of Viburnum plicatum ‘Lanarth’, the first report of this oomycete in the UK (and in Europe). Pathogenicity of a Py. kashmirense isolate was examined using a range of plant species. Inoculations were carried out under controlled conditions in the absence of other Pythium and Phytophthora species, on Glycine max (soya bean), Phaseolus vulgaris (common bean), Lupinus angustifolius (blue lupin), Cucumis sativa (cucumber) and Viburnum opulus. The majority of inoculations caused pre-emergence damping-off, as well as seed rot and root rot. In the in vitro assays, germination rates (%) of soya bean and blue lupin seeds were less than 50%; in the in vivo inoculations on plants, over 50% of soya bean, blue lupin and common bean plants died; in contrast, cucumber plants showed lower susceptibility in pathogenicity tests, with an approximately 80% germination rate in in vitro tests, and 25% dead plants in the in planta inoculations. Inoculations carried out on root systems of Viburnum opulus caused severe necrosis and root rot. Little research was previously conducted on pathogenicity of Py. kashmirense and its relationship with losses in crop yield and quality. The present study showed varying virulence on the different plant species tested after inoculation with Py. kashmirense. Despite the lack of clear host specialization, infection by Py. kashmirense decreased seedling survival and health of plants in a range of important agricultural and ornamental plant species. Full article

Capsicum annuum L. is a significant horticulture crop known for its pungent varieties and used as a spice. The pungent character in the plant, known as capsaicinoid, has been discovered to have various health benefits. However, its production has been affected due to various exogenous stresses, including diseases caused by a soil-borne pathogen, Pythium spp. predominantly affecting the Capsicum plant in younger stages and causing damping-off, this pathogen can incite root rot in later plant growth stages. Due to the involvement of multiple Pythium spp. and their capability to disperse through various routes, their detection and diagnosis have become crucial. However, the quest for a point-of-care technology is still far from over. The use of an integrated approach with cultural and biological techniques for the management of Pythium spp. can be the best and most sustainable alternative to the traditionally used and hazardous chemical approach. The lack of race-specific resistance genes against Pythium spp. can be compensated with the candidate quantitative trait loci (QTL) genes in C. annuum L. This review will focus on the epidemiological factors playing a major role in disease spread, the currently available diagnostics in species identification, and the management strategies with a special emphasis on Pythium spp. causing damping-off and root rot in different cultivars of C. annuum L. Full article

Rhizoctonia root-rot disease causes severe economic losses in a wide range of crops, including Vicia faba worldwide. Currently, biosynthesized nanoparticles have become super-growth promoters as well as antifungal agents. In this study, biosynthesized selenium nanoparticles (Se-NPs) have been examined as growth promoters as well as antifungal agents against Rhizoctonia solani RCMB 031001 in vitro and in vivo. Se-NPs were synthesized biologically by Bacillus megaterium ATCC 55000 and characterized by using UV-Vis spectroscopy, XRD, dynamic light scattering (DLS), and transmission electron microscopy (TEM) imaging. TEM and DLS images showed that Se-NPs are mono-dispersed spheres with a mean diameter of 41.2 nm. Se-NPs improved healthy Vicia faba cv. Giza 716 seed germination, morphological, metabolic indicators, and yield. Furthermore, Se-NPs exhibited influential antifungal activity against R. solani in vitro as well as in vivo. Results revealed that minimum inhibition and minimum fungicidal concentrations of Se-NPs were 0.0625 and 1 mM, respectively. Moreover, Se-NPs were able to decrease the pre-and post-emergence of R. solani damping-off and minimize the severity of root rot disease. The most effective treatment method is found when soaking and spraying were used with each other followed by spraying and then soaking individually. Likewise, Se-NPs improve morphological and metabolic indicators and yield significantly compared with infected control. In conclusion, biosynthesized Se-NPs by B. megaterium ATCC 55000 are a promising and effective agent against R. solani damping-off and root rot diseases in Vicia faba as well as plant growth inducer. Full article

Pine pitch canker (PPC) is a major threat to pine forests worldwide because of the extensive tree deaths, reduced growth, and degradation of timber quality caused by it. Furthermore, the aggressive fungus responsible for this disease (Fusarium circinatum) can also infect pine seeds, causing damping-off in young seedlings. This study proposes an approach based on coating treatments consisting of natural products to ensure seed protection. Seeds from two pine species (the most sensitive to this disease, Pinus radiata D. Don, and a more resistant one, Pinus sylvestris L.) were coated with single and binary mixtures of low and medium molecular weight chitosan and/or ethanolic-propolis extract. The germination rate, pre- and post-emergence mortality, total phenolic content, and radical scavenging activity were assessed. All treatments, and especially the one based on chitosan oligomers, had a beneficial impact on P. sylvestris seedlings, significantly enhancing survival rates and displaying a positive influence on the total phenolic content and on the seedlings’ radical scavenging activity. Conversely, non-significant negative effects on germination percentages were observed in the case of P. radiata seeds. The proposed treatments show promise for the protection of P. sylvestris seedlings against PPC. Full article