Pathogen Rhizoctonia Research Articles

Rhizoctonia species, anastomosis groups, and pathogenicity isolated from common bean in Lake Van Basin, Turkiye

Common bean (Phaseolus vulgaris L.) is an important vegetable crop grown in Lake Van Basin. Local genotypes are widely grown in the region. Rhizoctonia root rot induced by Rhizoctonia solani Kühn is an important soilborne plant disease that leads to global economic losses as well as in Turkey. The present study was conducted to determine anastomosis groups and pathogenicity of Rhizoctonia spp. obtained from bean plants in Lake Van Basin in 2013 and 2014. A total of 236 Rhizoctonia isolates in 5 anastomosis groups were obtained from bean plant roots. It was observed that AG- 4 (112) was the most isolated group in beans, followed by AG- 2 (41), AG- 3 (28), AG- 5 (33), and binucleate AG- K (22) isolates. Pathogenicity test conducted in thirty isolates in 5 anastomosis groups was analyzed for A64 (Bitlis/ Adilcevaz), TR68557 genotypes, and Gina (cv.) under growth chamber conditions. The study findings demonstrated that all tested isolates could infect the bean plant with different degrees of severity; however, the most virulent group was AG- 4. It was determined that the most virulent isolate was Isolate No. 19 in the A64 genotype, Isolate No. 2 in TR68557, and Isolate No. 18 in Gina cv. in in vivo tests. The identification and pathogenicity determination of Rhizoctonia isolates are the first steps towards an efficient control strategy for bean diseases caused by Rhizoctonia species. In order to obtain quality and productive products in the Van Lake Basin, where intensive bean production is carried out, precautions should be taken by considering the damage caused by Rhizoctonia spp. on plants.

Antioxidant, antifungal, and aphicidal activity of the triterpenoids spinasterol and 22,23-dihydrospinasterol from leaves of Citrullus colocynthis L.

Terpenoids from natural plant sources are valuable for their diverse biological activities that have important roles in the medical and agrochemical industries. In this study, we assessed the antioxidant, antifungal, and aphicidal activities of a mixture of spinasterol and 22,23-dihydrospinasterol from the leaves of Citrullus colocynthis. We used 1,1-diphenyl-2-picrylhydrazyl (DPPH) to assess antioxidant activity, and we measured antifungal activity using mycelium growth inhibition assays with three pathogenic fungi, Magnaporthe grisea, Rhizoctonia solani, and Phytophthora infestans. Aphicidal activity against adults of Myzus persicae was determined using in vitro and in vivo assays. Spinasterol and 22,23-dihydrospinasterol exhibited moderate antioxidant activity, even at lower concentrations: 19.98% at 0.78 µg mL−1, 31.52% at 3.0 µg mL−1, 36.61% at 12.5 µg mL−1, and 49.76% at 50 µg mL−1. Spinasterol and 22,23-dihydrospinasterol showed reasonable levels of fungicidal activity toward R. solani and M. grisea, with EC50 values of 129.5 and 206.1 µg mL−1, respectively. The positive controls boscalid and carbendazim were highly effective against all fungi except boscalid for M. grisea (EC50 = 868 µg mL−1) and carbendazim for P. infestans (EC50 = 8721 µg mL−1). Significant insecticidal activity was observed in both residual and greenhouse assays, with LC50 values of 42.46, 54.86, and 180.9 µg mL−1 and 32.71, 42.46, and 173.8 µg mL−1 at 72, 48, and 24 h, respectively. The antioxidant activity of spinasterol and 22,23-dihydrospinasterol was strongly positively correlated with their antifungal and insecticidal activity. Spinasterol and 22,23-dihydrospinasterol therefore show good antioxidant and aphicidal activity with moderate fungicidal activity, making them suitable candidates for an alternative to synthetic agents.

Biocontrol potential of Pseudomonas stutzeri endophyte from Withania somnifera (Ashwagandha) seed extract against pathogenic Fusarium oxysporum and Rhizoctonia solani

Agricultural crops are susceptible to abiotic and biotic factors. Among biotic factors, plant pathogens attacks are prominent and significantly reduce the crop productivity and production. Long term application of synthetic pesticides in agriculture not only causes resistance development in pathogens but also deteriorates the soil quality and pollutes the ecosystem. In the current study, an investigation has been made with an objective to isolate an endophytic bacterium from Withania somnifera seed and evaluate its potential biocontrol activity against soil-borne pathogens like Fusarium oxysporum var. ciceri and Rhizoctonia solani. The molecular approach of bacterium identification using 16S rRNA sequencing methods includes kit based DNA extraction and PCR amplification and the isolated endophytic bacterium was identified as Pseudomonas stutzeri. In dual culture assay, the endophytic bacterium P. stutzeri PSIISS-1 effectively suppressed growth of pathogenic fungi F. oxysporum var. ciceri (61.0%) and R. solani (53.3%), respectively. In vivo studies were conducted with initial microbial inoculum size of 108cell/ml and the studies revealed that the bacterium P. stutzeri PSIISS-1 co-inoculated with R. solani had significantly inhibited the sheath blight disease with the efficacy of 76% in susceptible paddy MTU-7029. Simultaneously, co-inoculation of P. stutzeri PSIISS-1 along with the pathogen F. oxysporum var. ciceri in chickpea JG-14 variety resulted in reduction of wilt symptom up to 80.45%. Bacterial inhibitions against the pathogens were corroborated with chitinase, protease and lipase enzymatic activities. Based on the results obtained from the study, P. stutzeri showed biocontrol activity against plant pathogens which can be used as potential bio-pesticides.

In-vitro and greenhouse management of banded leaf and sheath blight (BLSB) of maize, at Rampur, Chitwan, Nepal

The research included in-vitro experiments on the effect of the fungal antagonist (Trichoderma spp.) and fungicide (carbendazim) against BLSB pathogen (Rhizoctonia solani); and greenhouse experiment for the management of BLSB using antagonists (Trichoderma and Pseudomonas) and a fungicide (carbendazim) in different combinations. The in-vitro and greenhouse experiments were done at the plant pathology laboratory and greenhouse of Agriculture and Forestry University, Rampur, Chitwan. Of the isolates of Trichoderma evaluated against the BLSB pathogen in dual culture, the Trichoderma isolated from between healthy and diseased maize plants gave the maximum growth inhibition percent of the pathogen at 24 (19.86±0.52), 48 (51.63±0.40) and 72hours (72.78±1.11). Carbendazim at 10 ppm completely inhibited the growth of both the pathogen and Trichoderma on PDA medium, while at 1 ppm, the growth inhibition of the pathogen was (54.22±0.89) percent and of Trichoderma was (50.22±3.11) percent. The management experiment in a glasshouse with seven treatments was done in a randomized complete block design with three replications. Carbendazim alone gave the highest disease control (59.73%) with the lowest disease severity (28.67±0.67) and AUDPC per day (803.33±33.33). A combination of treatments alternately with Trichoderma and carbendazim also had a significant effect on reducing disease severity. In a separate experiment, Trichoderma with and without pathogen gave significantly higher shoot length, root length, shoot weight and root weight when compared with untreated control.

Functional characterization of the AGL1 aegerolysin in the mycoparasitic fungus Trichoderma atroviride reveals a role in conidiation and antagonism

Aegerolysins are small secreted pore-forming proteins that are found in both prokaryotes and eukaryotes. The role of aegerolysins in sporulation, fruit body formation, and in lysis of cellular membrane is suggested in fungi. The aim of the present study was to characterize the biological function of the aegerolysin gene agl1 in the mycoparasitic fungus Trichoderma atroviride, used for biological control of plant diseases. Gene expression analysis showed higher expression of agl1 during conidiation and during growth in medium supplemented with cell wall material from the plant pathogenic fungus Rhizoctonia solani as the sole carbon source. Expression of agl1 was supressed under iron-limiting condition, while agl1 transcript was not detected during T. atroviride interactions with the prey fungi Botrytis cinerea or R. solani. Phenotypic analysis of agl1 deletion strains (Δagl1) showed reduced conidiation compared to T. atroviride wild type, thus suggesting the involvement of AGL1 in conidiation. Furthermore, the Δagl1 strains display reduced antagonism towards B. cinerea and R. solani based on a secretion assay, although no difference was detected during direct interactions. These data demonstrate the role of AGL1 in conidiation and antagonism in the mycoparasitic fungus T. atroviride.

Identification of Novel QTL Conferring Sheath Blight Resistance in Two Weedy Rice Mapping Populations

BackgroundRice sheath blight (ShB) disease, caused by the pathogenic fungus Rhizoctonia solani, causes significant yield losses globally. US weedy rice populations, which are de-domesticated forms of indica and aus cultivated rice, appear to be more resistant to ShB than local japonica cultivated rice. We mapped quantitative trait loci (QTL) associated with ShB resistance using two F8 recombinant inbred line populations generated from crosses of an indica crop variety, Dee-Geo-Woo-Gen (DGWG), with individuals representing the two major US weed biotypes, straw hull (SH) and black hull awned (BHA).ResultsWe identified nine ShB resistance QTL across both mapping populations. Five were attributable to alleles that affect plant height (PH) and heading date (HD), two growth traits that are known to be highly correlated with ShB resistance. By utilizing an approach that treated growth traits as covariates in the mapping model, we were able to infer that the remaining four QTL are involved in ShB resistance. Two of these, qShB1–2 and qShB4, are different from previously identified ShB QTL and represent new candidates for further study.ConclusionOur findings suggest that ShB resistance can be improved through favorable plant growth traits and the combined effects of small to moderate-effect resistance QTL. Additionally, we show that including PH and HD as covariates in QTL mapping models is a powerful way to identify new ShB resistance QTL.

Toprak Kökenli Bitki Patojeni Funguslarla Mücadelede Biofumigasyonun Kullanım Olanakları

Fusarium, Rhizoctonia, Sclerotinia, Verticillium, Armillaria ve Rosellinia gibi toprak kökenli bitki patojeni funguslar, birçok bahçe ve tarla ürününde bitki ölümlerine ve verim kayıplarına sebep olan kök çürüklüğü hastalıklarına neden olmaktadır. Kök çürüklüğü hastalıklarının kontrolünde dayanıklı çeşit kullanımı, ürün rotasyonu, solarizasyon, fungisit uygulamaları ve toprak fumigasyonu gibi çeşitli mücadele yöntemleri uygulanmaktadır. Metil bromide ve kloropikrin gibi fumigantlarla yapılan toprak fumigasyonu toprak kökenli fungusların kontrolü için kullanılan en etkili yöntemlerden biridir. Ancak bu kimyasalların çevre ve insan sağlığına olumsuz etkilerinden dolayı dünyada ve ülkemizde kullanımı yasaklanmıştır. Bu nedenle, yeterli hastalık kontrolü sağlayan ve ticari fungisitlerle rekabet edebilen alternatif yöntemlerin araştırılmasına ihtiyaç vardır. Biofumigasyon kimyasal mücadeleye alternatif yöntemler arasında değerlendirilmekte nematodlar, yabancı otlar ve bazı fungusların neden olduğu hastalıkların mücadelesinde oldukça etkili olup, entegre mücadelenin bir parçası olarak kabul edilmektedir. Toprak kökenli fungusların kontrolünde örtücü bitkiler, organik gübre ve biyokatı atıklar biyofumigant olarak değerlendirilmektedir. Bu çalışmada toprak kökenli fungusların kontrolünde biyofumigasyon uygulamaları ve biyofumigantların funguslar üzerindeki etki şekilleri değerlendirilmiştir.

Volatiles and functional peptides compositions of Trichoderma variants induced by a new strategy of irradiation

Abstract Induction of mutation using gamma radiation improves the efficiency of Trichoderma against tomato fungal pathogens (Alternaria solani, Fusarium oxysporium, and Rhizoctonia solani). Results of the present study reveal the antagonistic activity of selected 2nd generation variants is higher than their 1st generation variants and the activity of latter variants is higher than their parent strains. The metabolites derived from irradiated variants are identified to understand their role in antibiosis interactions. GC/MS profile of volatiles emitted from T. viride Td1 and as its variants shows they are different in composition. The present study clears the potency of volatiles emitted from 2nd generation variant; T. viride Td1/2–3 to control tomato fungal pathogens using two strategies; applying the volatile compounds to tomato seeds or to soil infested with fungal pathogens. Results also showed the superiority of functional peptides originates from an irradiated variant; T. koningii Tk1/3-3 to control tomato fungal pathogens especially peptide fraction; F4 that characterized using LC/MS to fifteen sub-fractions having 12 amino acid residues or less; one of them is identified as peptabiotic.

Redistribution of iron and hydrogen peroxide in Pinus sylvestris roots in response to trophically diverse fungi

The simultaneous over-accumulation of Fe, hydrogen peroxide and superoxide can result in the generation of hydroxyl radicals, which play a significant role in the interactions between plant hosts and invading fungi. The physiological response to infection by pathogenic or mycorrhizal fungi may, however, be determined by the root zone. The objective of the present study was to use light microscopy to determine whether iron and hydrogen peroxide are differentially distributed in P. sylvestris roots in response to colonization by necrotrophic pathogens (Fusarium oxysporum and Rhizoctonia solani) vs. mycorrhizal fungi (Hebeloma crustuliniforme and Laccaria bicolor) in in vitro culture. It was also of interest to determine how hydrogen peroxide, superoxide, and iron added to substrate in vitro impacted the ability of trophically different fungi to grow. Infection by necrotrophic fungi, especially by F. oxysporum, were associated with a significantly higher accumulation of both forms of iron (Fe2+ and Fe3+) in the meristematic root zone, relative to the accumulation of these forms of iron in response to ectomycorrhizal fungi. Iron supplementation of solid culture medium reduced the growth of pathogenic fungi to a greater extent than the growth of mycorrhizal fungi. In contrast to the distribution of iron, cells in the elongation zone of P. sylvestris roots generally exhibited the highest accumulation of hydrogen peroxide. The growth of mycorrhizal fungi was more inhibited by the presence of hydrogen peroxide in the solid culture medium than by any other supplemented compounds. This research indicate that the distribution of iron and hydrogen peroxide in roots of P. sylvestris is related to the trophic strategy of the colonizing fungi.

Anastomosis group and pathogenicity of Rhizoctonia spp. associated with seedling damping-off of sugar beet in China

Between 2010 and 2015, 204 Rhizoctonia isolates were obtained from diseased sugar beet seedlings which collected from the sugar beet growing regions of China. On the basis of the morphological characteristics and sequence analysis of the internal transcribed spacers of the ribosomal DNA (rDNA ITS), 166 were identified as multinucleate Rhizoctonia (MNR), and 38 were binucleate Rhizoctonia (BNR), belonging to 15 species, anastomosis groups (AGs) or subgroups. The most prevalent was Rhizoctonia solani AG-4, with 49 isolates attributed to the subgroup HGIII, 47 to HGII, and 45 to HGI, followed by AG-K (31), AG-2-2IIIB (7), AG-A (6), AG-1-1C (4), AG-1-1B (3), AG-2-1 (3), AG-5 (3), AG-11 (2), AG-3 TB (1), Waitea circinata var. circinata (1), W. circinata var. zeae (1), and AG-C (1). Seventy-four representative isolates of all species, AGs or subgroups from different geographic origins were able to cause brown, dry lesions on roots of sugar beet seedlings or even seedling death with the disease incidence and the disease index ranging from 13.3 to 100% and from 1.9 to 97.1, respectively. The AG-4 isolates were the most aggressive on sugar beet seedlings. Moreover, the aggressiveness of the R. solani isolates was higher than that of the other isolates. To the best of our knowledge, this is the first detailed description of the AG composition of Rhizoctonia causing seedling damping-off on sugar beet in China.

Diversity and antagonistic potential of bacteria isolated from marine grass Halodule uninervis

The aim of this study was to isolate bacteria from sea grass, Halodule uninervis collected from the coastal area of Jeddah, Saudi Arabia and to screen them for antifungal and enzymatic activities. We have isolated 162 rhizo and endophytic bacteria from soil, roots, and leaves of the sea grass. Antifungal screening of isolated bacteria revealed 19 strains (11.7%) capable to inhibit growth of four pathogenic fungi, Pythium ultimum, Phytophthora capsici, pyricularia oryzae, and Rhizoctonia solani in an in vitro assay. Taxonomic and phylogenetic analyses on the basis of 16S rRNA gene sequence revealed 97–99.9% sequence identity to recognized species. Bacillus, Staphylococcus, Jeotgalicoccus, and Planococcus, within the Phylum Firmicutes, Kocuria, Arthrobacter, Ornithinimicrobium and Corynebacterium (Actinobacteria), Sulfitobacter, Roseivivax, Ruegeria (α-Proteobacteria), Moraxella, and Vibrio (γ-Proteobacteria), were isolated. Strains belong to Phylum Firmicutes remain dominant antagonistic bacteria in this study. Further hydrolytic enzyme production was determined for these antagonistic bacteria. Our results demonstrated that the sea grass represents an important source of diverse antagonistic bacteria capable of producing antifungal metabolite.

Inhibition Activity of Mycorrhizal Fungi Glomus mosseae and G. intradicas with Trichderma harizanum Against Rhizoctonia solani in Okra Plant Abelmoschus esculentus (L.)

The agricultural production processes currently targeted reducing chemical fungicides usage and increasing bio-agent application through controlling diseases alone or integrating it with other factors. The study aimed to investigate the induction of systemic resistance by multi bio-agents represented by mycorrhizal fungi Glomus mosseae, G. intradicas and Trichoderma harizanum against pathogenic fungus Rhizoctonia solani which caused wilt disease and growth defoliation to Okra seedling. Three isolate of R. solani were recorded on root of Okra seedling, named (local - Batra). Isolate no. (3) was more virulence than other isolates in damping off disease in the pre and post emergence. Results also showed that G. mosseae and G. intradicas with T. harizanum had a positive influence in reducing detrimental effect of R. solani in all growth parameters (e.g. fresh and dry weight of root) on disease severity on Okra plant caused by R. solani. Bio-agents (G. mosseae,G. intradicas and T. harizanum) increased resistance in Okra plants by raising production of enzymescatalase and Peroxidase.this experiment was revealed that using a complex of bio-agent’s factors were greatly increase the efficiency of biological control than using each of them individually. We conclude that the broad diversity of rhizosphere micro-organisms as well as the confronting between the bio-chemical and physical changes could be reflected the variations in the metabolic secondary products that could inhibit pathogens.

A New Antifungal Antibiotic from Bacillus sp. KM5 Isolated from Rice Rhizospheric Soil

Bacterial strain, Bacillus sp. KM5 was recently isolated and characterized by strong antifungal activities against several agronomically important filamentous pathogenic fungi including Rhizoctonia solani Nees. This is a new study to characterize four prominent antibiotics synthesized by Bacillus sp. KM5 (termed M1, M2, M3, and M4), isolated from rice rhizospheric soil. Lipopeptide profiling and spectroscopic characterizations of antibiotics M1 and M2 identified them as Bacillomycin F and Bacillomycin D, respectively. Antibiotic M3 was recognized as another iturinic lipopeptide Bacillopeptin A. Finally, M4 emerged as a novel straight chain polyhydroxy polyether compound with a single double bond, indicating a non-polyene structure with no prior mention in the literature. Furthermore, in vitro bioassay of M4 showed maximum activity against Rhizoctonia solani among five plant pathogenic fungi. This research could help in developing new or improved antifungal formulations or novel strategies to prevent fungal spoilage.

PGPRs of plum (Prunus domestica) rhizosphere enhance plant growth and antagonise fungal activity in vitro

ABSTRACTPlant growth promoting rhizobacteria (PGPR) promote the plant growth by various direct and indirect mechanisms. The present study was undertaken to isolate and characterise the PGPRs of plum (Prunus domestica) rhizosphere in Pakistan. A total of 95 rhizobacteria were isolated, out of which 40 strains were selected on the basis of morphological, biochemical and Gram staining characteristics. The selected isolates were screened for in vitro plant growth promoting potential and were subsequently evaluated for host plant growth promotion. The selected isolates demonstrated strong lytic enzymatic activities and were able to produce ammonia, siderophore, Hydrogen cyanide along with capability of phosphate solubilisation. Moreover, the results showed a significant growth suppression of pathogenic Fusarium oxysporum and Rhizoctonia solani in an in vitro assay. The plant microbe interaction study was carried out using 11 most efficient rhizobacterial strains inoculated to roots of plum plants. The inoculated PGPRs significantly augmented the leaves number per shoot, shoot diameter, shoot length and plant height. The inoculation also significantly increased the chlorophyll contents of leaves, concentration of micro and macro nutrients compared with control. The current study shows the importance of these selected PGPRs as bio-fertilizer to improve the health and productivity of plum species in Pakistan.

In-Vitro Inhibition of Pythium ultimum, Fusarium graminearum, and Rhizoctonia solani by a Stabilized Lactoperoxidase System alone and in Combination with Synthetic Fungicides

Advances in enzyme stabilization and immobilization make the use of enzymes for industrial applications increasingly feasible. The lactoperoxidase (LPO) system is a naturally occurring enzyme system with known antimicrobial activity. Stabilized LPO and glucose oxidase (GOx) enzymes were combined with glucose, potassium iodide, and ammonium thiocyanate to create an anti-fungal formulation, which inhibited in-vitro growth of the plant pathogenic oomycete Pythium ultimum, and the plant pathogenic fungi Fusarium graminearum and Rhizoctonia solani. Pythium ultimum was more sensitive than F. graminearum and R. solani, and was killed at LPO and GOx concentrations of 20 nM and 26 nM, respectively. Rhizoctonia solani and F. graminearum were 70% to 80% inhibited by LPO and GOx concentrations of 242 nM and 315 nM, respectively. The enzyme system was tested for compatibility with five commercial fungicides as co-treatments. The majority of enzyme + fungicide co-treatments resulted in additive activity. Synergism ranging from 7% to 36% above the expected additive activity was observed when P. ultimum was exposed to the enzyme system combined with Daconil® (active ingredient (AI): chlorothalonil 29.6%, GardenTech, Lexington, KY, USA), tea tree oil, and mancozeb at select fungicide concentrations. Antagonism was observed when the enzyme system was combined with Tilt® (AI: propiconazole 41.8%, Syngenta, Basel, Switzerland) at one fungicide concentration, resulting in activity 24% below the expected additive activity at that concentration.

Molecular identification and pathogenicity of Rhizoctonia spp. recovered from seed and soil samples of the main bean growing area of Argentina

Fil: Spedaletti, Yamila Andrea. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Salta-Jujuy. Estacion Experimental Agropecuaria Salta; Argentina

Synthesis and characterization of chitosan\u2013copper nanocomposites and their fungicidal activity against two sclerotia-forming plant pathogenic fungi

In this report, the metal-vapor synthesis (MVS) was used for the preparation of copper nanoparticles which was then used for the preparation of chitosan–copper nanocomposite. The antifungal activity of Cu@Chit NCs against two sclerotium-forming plant pathogenic fungi Sclerotium rolfsii (S. rolfsii) and Rhizoctonia solani (R. solani) AG-4 was evaluated in vitro and their effects on hyphal morphology, and sclerotia formation were observed for the first time. The NCs were prepared through impregnation of chitosan with colloid solution of copper nanoparticles in organic solvent (acetone or toluene). Transmission electron microscopy shows that the particles have predominantly spherical form, polydisperse character, the mean diameter about 2–3 nm and a rather uniform distribution in the chitosan matrice. Analysis of the small angle scattering curves suggests that the copper particles in the NCs with the size of ≤2 nm are mostly located in the chitosan pores with the same size. The effect of Cu@Chit NCs on fungal growth reveals some significant inhibitory activity against two tested fungi. The highest level of inhibition against S. rolfsii and R. solani AG-4 was observed using the high concentrations of Cu@Chit NC prepared using acetone as a solvent. A loss of the cytoplasm content, cytoplasmic coagulation, irregular shape of mycelia, or destruction in the hyphae was confirmed. The experiments demonstrate that the Cu@Chit NC synthesized via MVS using acetone was more effective than that of toluene in inhibiting fungal hyphae growth against R. solani AG-4 and S. rolfsii. The results show that the Cu@Chit NCs are fungicidal against both the tested fungus at high concentrations and the fungicidal or fungistatic activity is dependent on the tested fungus species.

Characterization and pathogenicity of Rhizoctonia SPP. isolated from vegetable crops grown in greenhouses in Samsun province, Turkey

A total of one hundred and five isolates of Rhizoctonia belonging to 7 anastomosis groups (AGs) were obtained from the diseased roots and rhizosphere soils of bean, cucumber, eggplant, pepper and tomato plants grown in greenhouses in Samsun province (Black Sea region, Turkey) during the period 2011–2012. The isolates of Rhizoctonia spp. were examined for their cultural characteristics, anastomosis groups and pathogenicity. Of these, 83.8% were multinucleate Rhizoctonia solani (AG-2, AG-4, AG-5 and AG-6) and 16.2% were binucleate Rhizoctonia (AG-A, AG-E and AG-F). Sixty five of the isolates belonged to AG-4 which was the most frequent group (61.9%) in all greenhouses surveyed. Numbers of the isolates belonging to AG-2 (7.6%), AG-5 (6.7%) and AG-6 (7.6%) were 8, 7 and 8, respectively. Seventeen isolates recovered from greenhouses surveyed were identified as binucleate Rhizoctonia AG-A (1.9%), AG-E (6.7%) and AG-F (7.6%). All isolates of Rhizoctonia spp. tested for growth rates grew at temperatures of 10, 15, 20, 25 and 30°C, whereas they were completely inhibited at 5°C. The results of pathogenicity tests showed that the differences in virulence among isolates of Rhizoctonia spp. were statistically significant ( P < 0.001). The tests on bean seedlings showed that the highest disease severity was caused by AG-4 isolates. The disease severity index (DSI) of the R. solani AG-4 isolates ranged from 3.2 to 3.8. In addition, the isolates of three AGs belonging to binucleate Rhizoctonia spp. were generally found to be moderately virulent (DSI 2.0–2.4).

Antifungal and antiproliferative activities of endophytic fungi isolated from the leaves of Markhamia tomentosa

Context: Plants harbor endophytes with potential bioactivity. Markhamia tomentosa (Benth) K. Schum ex. Engl. (Bignoniaceae) is reported to possess antioxidant, anti-inflammatory and anticancer activities. Objective: The antifungal and antiproliferative properties of endophytic fungi extracts and fractions from M. tomentosa were evaluated. Material and methods: Endophytic fungi were isolated from the leaves of M. tomentosa and identified by ITS-rDNA sequence analysis. The antagonistic effect of the fungal strains was investigated against pathogenic fungi viz, Fusarium oxysporum, Sclerotinia sclerotiorium, Rhizoctonia solani, and Botrytis cinerea using the dual culture assay for 5–7 days. Antiproliferative effect of the fungal extracts and fractions (3.91–250 μg/mL) on HeLa cancer cell line was tested and IC50 was calculated. Poisoning food assay and antifeedant activity against the pathogenic fungi and Spodoptera litura larvae, for 7 days and 2 h, respectively, was also tested at concentrations of 250, 500 and 1000 μg/mL. Results: Fungal endophytes Trichoderma longibrachiatum and Syncephalastrum racemosum were isolated from the leaves of M. tomentosa. Isolated endophytic fungal strains and solvent extracts showed MIC value of 1000 μg/mL against tested pathogenic fungi in the dual culture and poisoning food assays. Methanol fraction of S. racemosum isolate showed the most effective antiproliferative activity with IC50 of 43.56 μg/mL. Minimal feeding deterrent activity against S. litura larvae was also observed. Discussion and conclusion: These findings showed that the leaves of Markhamia tomentosa harbor strains of endophytic fungi with promising health benefits, and suggest their antifungal and antiproliferative effects against pathogenic fungi and HeLa cancer cell line.

Characterization and pathogenicity of Rhizoctonia spp. isolated from winter squash in the Black Sea region of Turkey

A total of 27 isolates of Rhizoctonia spp. were recovered from diseased winter squash (Cucurbita maxima) plants, collected from Amasya, Ordu, Samsun and Sinop provinces in the Black Sea region, Turkey. The isolates of Rhizoctonia spp. associated with root and crown rot of winter squash were examined for their cultural characteristics, anastomosis groups and subgroups using sequence analyses of the rDNA-ITS and pathogenicity. Based on ITS1–5.8S-ITS2 rDNA sequencing, Rhizoctonia solani anastomosis group (AG) 4 was the pathogen most frequently recovered (42.8 %) in all fields surveyed. Twenty-four isolates of R. solani AG 4 were further divided into three subgroups, AG 4 HG-I (13), AG 4 HG-II (6) and AG 4 HG-III (5). In addition, three isolates recovered from different fields were identified as binucleate (BN) Rhizoctonia AG A (7.4 %) and AG K (3.7 %). All isolates grew at temperatures of 10, 15, 20, 25, 30 and 35 °C, and they were completely inhibited at 5 and 40 °C. The results of pathogenicity tests on winter squash seedlings showed statistically significant differences (P < 0.001) among the mean disease severity index (DSI) of three subgroup isolates of R. solani AG 4. The DSI of the isolates of R. solani AG 4 ranged from 2.0 to 5.0. Isolates of AG 4 HG-I and HG-III had the highest virulence levels (DSI ranged from 3.8 to 5.0). The virulence level of isolates of BN Rhizoctonia AG A and AG K were low (DSI ranged from 2.0 to 2.3). To our knowledge, this is the first report of R. solani AG 4 HG-I, HG-II, and HG-III, and BN Rhizoctonia AG A and AG K occurring on winter squash, one of the most important cucurbit species in Turkey.