Solani Growth Research Articles

Bacterial Tomato Pathogen Ralstonia solanacearum Invasion Modulates Rhizosphere Compounds and Facilitates the Cascade Effect of Fungal Pathogen Fusarium solani.

Soil-borne pathogen invasions can significantly change the microbial communities of the host rhizosphere. However, whether bacterial Ralstonia solanacearum pathogen invasion influences the abundance of fungal pathogens remains unclear. In this study, we combined high-throughput sequencing, qPCR, liquid chromatography and soil culture experiments to analyze the rhizosphere fungal composition, co-occurrence of fungal communities, copy numbers of functional genes, contents of phenolic acids and their associations in healthy and bacterial wilt-diseased tomato plants. We found that R. solanacearum invasion increased the abundance of the soil-borne pathogen Fusarium solani. The concentrations of three phenolic acids in the rhizosphere soil of bacterial wilt-diseased tomato plants were significantly higher than those in the rhizosphere soil of healthy tomato plants. In addition, the increased concentrations of phenolic acids significantly stimulated F. solani growth in the soil. Furthermore, a simple fungal network with fewer links, nodes and hubs (highly connected nodes) was found in the diseased tomato plant rhizosphere. These results indicate that once the symptom of bacterial wilt disease is observed in tomato, the roots of the wilt-diseased tomato plants need to be removed in a timely manner to prevent the enrichment of other fungal soil-borne pathogens. These findings provide some ecological clues for the mixed co-occurrence of bacterial wilt disease and other fungal soil-borne diseases.

The profile change of defense pathways in phaseouls vulgaris L. by biochemical and molecular interactions of Trichoderma harzianum transformants overexpressing a chimeric chitinase

Trichoderma species as biocontrol agents protect plants against several pathogens via multiple mechanisms. This study was aimed to evaluate the in vitro biocontrol activities and, as well as in vivo induction of systemic resistance of Phaseolus vulgaris L. by two Trichoderma harzianum transformants overexpressing a chimeric chitinase42 with chitin binding domain (T13 and T15) and wild-type (Tw) strain with and without Rhizoctonia solani. In order to achieve this goal, T. harzianum strains were compared in vitro for their potential to antagonize activity against R. solani. Also, the expression of biocontrol-associated genes (chit42 and qid74) and the volatile compounds (VOCs) profile with biocontrol activity was analyzed from T. harzianum strains. The real-time PCR was used to measure the expression of defense-related genes involved in systemic acquired resistance (SAR) and induced systemic resistance (ISR) pathways. The results showed that recombinant strains T15 (92%) and T13 (85%) had the higher inhibitory effects against R. solani compared to the Tw strain. Also, gene expression analysis of T. harzianum revealed the up-regulation of biocontrol-associated genes in recombinant strains. Analysis of VOCs from three T. harzianum strains identified a total of twenty-two compounds, including five that were produced by all of them .VOCs analysis of recombinant strains revealed the production of compounds, like caryophyllene oxide, 2-methyl-1-butanol, α-farnesene, and β-bisabolene. These compounds had been reported to induce plant defensive reactions against stress. Inoculation of plants with T13 and specially T15 strains, restricted the R. solani growth. Treatment of bean plants with recombinant strains led to increase in protection mechanisms including enhanced defense enzymes activity and higher expression of defense-related genes, as compared with Tw. The ability of recombinant strains to have better colonization within the soil and the root surface, describes its positive effects on defense mechanisms against R. solani.

Allyl Isothiocyanate (AITC) Triggered Toxicity and FsYvc1 (a STRPC Family Member) Responded Sense in Fusarium solani.

Allyl isothiocyanate (AITC) is a natural product used as a food additive. Due to its strong volatility and broad biological activity, AITC is considered as a bio-fumigant to control soil-borne fungal diseases in agriculture, creating an urgent need for evaluation of the antifungal activity of AITC. Here we study the effect of AITC on Fusarium solani growth and explore the molecular mechanisms. The results indicated that AITC causes rapid inhibition of F. solani after 5 min, hyphal deformity, and electrolyte leakage. A yeast-like vacuolar transient receptor potential channel regulator (FsYvc1, a STRPC family member) was identified in F. solani that seems to play a role in this fungi AITC sensitivity. Genetic evidence suggests the gene FsYvc1 is involved in F. solani growth, development, and pathogenicity. Loss of FsYvc1 resulted in hypersensitivity of F. solani to AITC and induced reactive oxygen species (ROS) accumulation ∼ 1.3 to 1.45- folds that of the wild type (WT), and no difference responses to CaCl2, NaCl, KCl, SDS, and Congo red when compared with WT. In addition, ΔFsYvc1-17 showed significantly reduced (∼ 1-fold) glutathione-S-transferase (GST) expression compared with the WT without AITC induction. Upon exposure to 4.8 μg/mL AITC for 3 h, the relative expression levels were ∼ 12–30 fold higher in both the WT and ΔFsYvc1-17. Nevertheless, no difference in GST expression level was observed between the WT and ΔFsYvc1-17. The current study provides novel insights into the toxicity mechanisms of AITC. Considering our results that show the key role of FsYvc1, we propose that it could act as a new molecular target for future fungicide development.

Influence of rootstock genotype on efficacy of anaerobic soil disinfestation for control of apple nursery replant disease

Apple replant disease (ARD) in production nurseries can negatively impact commercial viability by diminishing tree quality and potentially serving as a source of pathogen inoculum. The current study was carried out to determine the potential for plant genotype to influence anaerobic soil disinfestation (ASD) disease control efficacy. M.9, G.41, and G.935 apple rootstock genotypes were employed. ASD was conducted using orchard grass as the carbon input (10 t ha−1 or 20 t ha −1). Rootstock growth in ASD-treated soils was comparable to that attained in response to soil pasteurization or fumigation with 1,3-dichloropropene/chloropicrin (FUM) in both greenhouse (GT) and nursery field trials (NFT). In GT, Rhizoctonia solani AG-5 root infection and growth performance varied with rootstock genotype and soil treatment. ASD reduced pathogen DNA quantity in roots and improved rootstock growth. Genotype, but not soil treatment, influenced root infestation by Pythium ultimum and R. solani in the NFT. ASD with grass input at 20 t ha −1 improved soil nutrient levels, especially NO3− N, and provided significant weed control in the NFT. Treatments significantly altered composition of the bulk soil and rhizosphere microbiome in GT and these effects were prolonged in ASD-treated soils. In NFT, ASD conducted with orchard grass was uniformly as effective as FUM in the control of ARD and increase in trunk diameter increment, the primary determinant of apple rootstock value. This ASD treatment can be suggested as a potential method for effective control of nursery replant disease across rootstock genotypes varying in disease tolerance.

Effect of heterocystous nitrogen-fixing cyanobacteria against rice sheath blight and the underlying mechanism

Rice sheath blight causes serious damage to rice crops in China. The most common practice for rice sheath blight control is still chemical treatment, an environmentally unfriendly way. Studies have demonstrated the use of nitrogen-fixing cyanobacteria to prevent crop diseases as well as to improve soil fertility and crop productivity. However, little information is available on the biocontrol of rice sheath blight using cyanobacteria. Therefore, the objective of the present study was to screen and evaluate the biocontrol effect of nitrogen-fixing cyanobacteria against the disease through microchamber and microarea experiments. Based on the results of the microchamber experiment, three strains (SCAU04, SCAU15, and SCAU26) out of nine nitrogen-fixing cyanobacterial strains with a significant inhibition (>80%) on rice sheath blight were selected. Further, microarea experiments during two seasons demonstrated the highest disease control efficacy (54.5%) on day 20 with SCAU26 treatment. Moreover, the algal treatments significantly promoted root length, underground biomass, and number of grains per panicle. SCAU04 and SCAU26 treatments significantly improved the rice theoretical yield and significantly (P < 0.05) enhanced soil potassium content compared with the control group without algal treatment. The extract of SCAU04, SCAU15, and SCAU26 algal cells inhibited the mycelial growth of R. solani (inhibition rate; 90.12%, 78.33%, and 89.87%, respectively). Based on gas chromatography–mass spectrometry results, eight metabolites were selected and evaluated for their activity against R. solani. Among them, seven inhibited R. solani growth; diisooctyl adipate showed the highest inhibitory effect. All three cyanobacteria produced the phytohormones salicylic acid, auxins, and cytokines. The salicylic acid and trans-zeatin-riboside contents of SCAU04 were 3654.74 ng g−1 and 5266.67 ng g−1, respectively. The isopentenyladenine content of SCAU26 reached 2839.98 ng g−1. Morphological and molecular analysis identified the best two strains SCAU04 and SCAU26 as Nostoc piscinale and Anabaena variabilis, respectively. To conclude, our findings indicate that cyanobacteria produce bioactive substances to inhibit R. solani, secrete phytohormones to promote plant growth and induce plant disease resistance, and improve soil nutrient content to support plant growth.

Bakteri Endofit dari Tumbuhan Paku-pakuan sebagai Agens Hayati Rhizoctonia solani dan Pemacu Pertumbuhan Tanaman Padi

Rhizoctonia solani merupakan salah satu patogen penting penyebab penyakit hawar seludang pada tanaman padi. Patogen ini termasuk yang sulit dikendalikan karena bersifat kosmopolit, mampu bertahan di dalam tanah, dan memiliki kisaran inang yang banyak. Pengendalian secara biologi dengan bakteri endofit merupakan salah satu alternatif yang potensial karena kemampuannya hidup di dalam jaringan tanaman tanpa menimbulkan gejala penyakit dan dapat meningkatkan pertumbuhan serta ketahanan tanaman. Tujuan penelitian ini ialah mengeksplorasi bakteri endofit dari bagian batang akar dari tiga jenis tumbuhan paku yang berbeda, yaitu Salvinia molesta (paku air), Pteris ensiformis (paku terestrial), dan Drymoglossum pilosolloides (paku epifit) dan mengevaluasi potensinya sebagai agens hayati R. solani dan pemacu pertumbuhan tanaman. Isolasi bakteri dilakukan pada medium tripsic soy agar (TSA) dan nutrient agar (NA). Isolat bakteri dimurnikan dan diuji keamanan hayati dengan uji hipersensitifitas dan hemolisis. Hasil penelitian diperoleh 178 isolat bakteri endofit dan sebanyak 88 isolat menunjukkan reaksi negatif pada uji hipersensitisfitas dan uji hemolisis. Selanjutnya, isolat tersebut diuji dual test secara in vitro terhadap R. solani dan didapatkan 4 isolat bakteri endofit (APE15, APE22, APE33, dan APE35) dengan daya hambat dari 27–76% pada medium TSA, agar-agar dekstrosa kentang (ADK), dan TSA + ADK. Hasil uji pertumbuhan empat isolat terhadap benih padi varietas Situ Bagendit menunjukkan bahwa bakteri endofit mampu meningkatkan persentase perkecambahan padi 4.9% – 48.8%, meningkat panjang akar padi 68.3%–95.4%, panjang pucuk 53.2%–87.3%, bobot segar 49.07%–90.65%, dan bobot kering 48.1%–87.3%. Hasil ini menunjukkan bahwa tumbuhan paku mengandung beberapa bakteri endofit yang dapat dikulturkan dan memiliki senyawa antimikrob yang efektif, serta dapat digunakan sebagai sumber agens hayati terhadap patogen R. solani dan pemacu pertumbuhan tanaman.

A β‐1,3‐glucanase gene from Panax notoginseng confers resistance in tobacco to Fusarium solani

β‐1,3‐glucanases are members of the pathogenesis‐related protein (PR)-2 family, and they play important roles in defense response in plants. A β‐1,3‐glucanase gene was isolated from Panax notoginseng and named as PnGlu1 in this study. This gene encodes a protein of 379 amino acids containing a potential signal peptide, and subcellular localization analysis confirmed that PnGlu1 protein was localized in the cell wall. The PnGlu1 expression level in P. notoginseng roots was evidently induced by Methyl jasmonate, salicylic acid, ethylene, and hydrogen peroxide treatment. Moreover, the PnGlu1 gene showed high transcription level after inoculation with Fusarium solani, which is the important agent of P. notoginseng root rot disease. In addition, the PnGlu1 recombinant protein expressed in Escherichia coli showed a high-level inhibitory activity against Fusarium solani and Fusarium oxysporum growth. Furthermore, the plant overexpression vector pCAMBIA2300s-PnGlu1 was constructed and overexpressed in tobacco (Nicotiana tabacum L. cv Xanthi). The transgenic tobacco plants showed strong resistance to F. solani infection. Additionally, the gene expression levels of some jasmonic acid biosynthesis genes and PRs were significantly up-regulated in the PnGlu1 transgenic tobacco lines. This study indicated that the PnGlu1 is a vital defense gene during response to F. solani.

Evaluation the potential of indigenous biocontrol agent Trichoderma harzianum and its interactive effect with nanosized ZnO particles against the sunflower damping-off pathogen, Rhizoctonia solani

Rhizoctonia solani is a phytopathogenic fungus affecting a wide range of plants hosts including the sunflower causing various diseases such as damping-off. Current management approaches of this pathogen are inadequate. Aim of this study was to assess the potential of eco-friendly control methods, the indigenous biocontrol fungus Trichoderma harzianum and ZnO nanoparticles for controlling of the sunflower damping-off pathogen, R. solani. The biocontrol agent T. harzianum showed a high antagonism effect on R. solani growth. Additionally, growth of R. solani was significantly (p = 0.01) reduced gradually by presence of various concentrations of the ZnO NPs indicating to concentration-dependent toxicity effect. However, a similar impact was also observed on growth of T. harzianum. On the other hand, the percentage of seed germination and stem length of sunflower (Coban cv.) did not affect significantly by ZnO NPs. Conversely, the root lengths were significantly decreased. In the horticultural canopy trial, the best reduction to the sunflower damping-off incidence percentage was achieved by treatment of sunflower seedlings growing in compost inoculated with T. harzianum and R. solani 68.75% comparing to 100% in the control. In contrast, a significant reduction in severity percentage of damping-off symptoms was accomplished in most of the treatments. The best suppression was achieved in treatments of spraying the seedlings with ZnO NPs (15 mg/ml) in two days prior of planting that was 50% in compression with 97.50% in control. These findings can justify the application of the local biocontrol agent T. harzianum alone or in integration with ZnO NPs to be included with current management approaches of sunflower damping-off, which could lead to a diminution in the utilizing of fungicides.

Antagonistic Potential of Macrolepiota sp. Against Alternaria Solani as Causal Agent of Early Blight Disease in Tomato Plants

The aim of this study was to identify a Mexican native basidiomycete strain with antagonistic potential against phytopathogenic fungi. The antifungal activity of fifteen isolates against Fusarium oxysporum, Fusarium solani, Colletotrichum truncatum, Colletotrichum coccodes, Colletotrichum sp., Stemphylium solani, Botrytis cinerea, Epicoccum nigrum, Phomopsis sp. and Alternaria solani was studied in vitro using dual culture assay. An isolate of Macrolepiota sp (CS185) exhibited the strongest ability to compete on potato dextrose agar medium (PDA) causing 22.2 up to 46.6% inhibition in seven out of ten pathogens evaluated. The addition of 30% Macrolepiota sp. liquid filtrates (from 7 day-cultures in potato dextrose broth) to PDA plates inhibited 66% of A. solani growth. Application of Macrolepiota sp. CS185 culture fluids to control early blight disease caused in tomato plants by A. solani under greenhouse conditions diminished disease incidence and percent of damage. The length of the stems, the roots and the foliar area increased in the treated plants and, above all, the foliar symptoms decreased by 73%. Sesquiterpene lactones and quinones identified in culture fluids might be responsible for Macrolepiota antifungal activity. This study proves that Macrolepiota sp. CS185 culture filtrates have potential in biocontrol of early blight disease.

Occurrence and Biological Control of Cucumber Damping Off Disease under Protected Cultivation in Sulaimani, Iraq

Occurrence and cucumber damping-off disease incidence was determined in Sulaimani plastic houses in 2014 revealed from overall disease incidence of 6.82%. The highest incidence and severity reached to 23.7% and 5.0 respectively in Kharajian. While the lowest incidence and severity was detected in Arabit (0.2% and 0.6 respectively). Disease symptoms include pre and post-emergency damping-off of cucumber seedlings. Twelve fungal pathogens were isolated from roots and crown of infected seedlings and plants that explore typical damping-off and root rot symptoms. Rhizoctonia solani was the most frequently isolated fungi followed by Pythium aphanidermatum, Fusarium solani and Pythium sp. Morphology and characteristics of R. solani and P. aphanidermatum match with the original described characters of the fungi. The optimum growth temperature for P. aphanidermatum was 30°C and for R. solani was between 25-30°C. Pathogenicity test revealed that R. solani significantly surpassed all other treatment except P. aphanidermatum by inciting 53.3% pre and 66.4% post-emergency damping-off followed by P. aphanidermatum that incited 43.6% and 56.3% pre and post emergency damping-off respectively. T. harzianum showed high antagonistic ability against both pathogens. Antagonistic ability degree of T. harzianum reached to 37.02 against P. aphanidermatum and 32.00 against R. solani. The bio-control bacterial Bacillus subtilis, Rhizobacteria, Streptomyces coelicolor showed high efficiency in controlling the disease. Rhizobacteria and S. coelicolor completely inhibit R. solani growth at 10-1 bacteria dilution and significantly surpassed all other treatments. dilution 10-1 from all the used bacteria were significantly more efficient against P. aphanidermatum. This dilution was contain 21.4 × 107 cell forming unit in each milliliter (CFU/ml) in B. subtilis, 28 × 107(CFU/ml) in Rhizobacteria, 29.5 × 107 (CFU/ml) in S. coelicolor, 32.2× 107(CFU/ml) in Pseudomonas flouresence and 22.6 × 107 (CFU/ml) in Azotobacter chroococcus.

Inhibition of Tomato Early Blight Disease by Culture Extracts of a Streptomyces puniceus Isolate from Mangrove Soil.

This study investigates the potential of natural products derived from a mangrove rhizosphere bacterium in tomato early blight management. A Streptomyces puniceus strain L75 was isolated from the rhizosphere of Acanthus ilicifolius Linn in the Mai Po Reserve, Hong Kong. The crude ethyl acetate (EA) extract of L75 fermentation cultures has broad-spectrum antifungal bioactivities. L75 EA extract was significantly more effective in Alternaria solani growth inhibition at 25 μg/ml or lower compared with Mancozeb, with no observable negative impacts on tomato leaves or root development. Furthermore, L75 EA extract had significantly lower aquatic toxicity than Mancozeb at the same concentrations. L75 EA extract targets germ tube elongation of A. solani conidia, with a fungistatic mode of action. Liquid chromatography-quadrupole time-of-flight mass spectrometry analysis identified two possible antifungal compounds, Alteramide A and the Heat-Stable Antifungal Factor, which together contribute partially to the bioactivity of L75 EA extract. On detached tomato leaves, coinoculation of A. solani with L75 EA extract of 50, 25, or 5 μg/ml reduced diseased areas by ∼98, ∼90, and ∼48%, respectively, relative to the control after 5 days. This study demonstrates the potential of natural products from mangrove rhizosphere bacteria in agricultural applications.

Comparative Study on Effects of Chemical Fungicides and a Biocide on Cotton Seedling Damping-Off Caused by Rhizoctonia solani

The present study evaluated the efficacy of the fungicides Moncut and Rizolex-T and the biocide Bio-Control T34 (Trichoderma asperellum) on suppressing incidence of cotton seedling damping-off caused by Rhizoctonia solani on cotton cultivar Giza 86. The dual treatments of the two fungicides and the biocide also evaluated in vitro and in vivo. In vitro studies showed that Moncut completely inhibited R. solani linear growth when it was applied at a rate of 250ppm, while Rizolex-T completely inhibited R. solani growth when it was applied at a rate of 125ppm. The biocide inhibited the linear growth of R. solani by 59.17%. The biocide growth was not affected by all the applied concentrations of Moncut, while it was partially inhibited by the high concentrations of Rizolex-T. Under greenhouse conditions, the two chemical fungicides suppressed incidence of damping–off, while the biocide was unable to suppress the disease. The use of Moncut before or after the biocide succeeded in reducing the disease incidence. On the other hand, Rizolex-T caused significant reduction in disease incidence only when it was applied before the biocide. The application half or fourth the initial dose of the chemical fungicides before or after the biocide caused significant reduction in the disease incidence. The application of Moncut by the initial dose followed by the biocide caused increases in the activity of polyphenol oxidase (PPO) and phenols and sugars contents of the seedlings. Application half the initial dose of Moncut before or after the biocide caused increases in the previously mentioned variables. The use fourth the initial dose of Moncut caused increases in the same variables when it was followed by the biocide, while the use of this dose after the biocide caused decreases in the same variables.

Evaluation of an integration between the nanosized zinc oxide and two cultivars for the control of dampingoff disease in sunflower crop

Damping-off disease, caused by Rhizoctonia solani, leads to severe worldwide economic losses in many important crops. The current strategies to control this disease are inadequate. This study addresses the possibility of using ZnO nanoparticles (NPs) and two cultivars of sunflower to be employed in control strategies. The ZnO NPs were significantly (P=0.01) more inhibitory to R. solani growth at high concentrations than lower treatments indicating a dose-dependent effect. This effect was found to be fungistatic when fungal inoculum was transferred to standard medium after challenging with the ZnO NPs. Additionally, the two cultivars of sunflower tested were found to be susceptible to pathogen R. solani showing a high percentage of damping-off incidence and severity of symptoms. Although, most treatments of ZnO nanoparticles applied did not significantly reduce the damping-off incidence, the disease severity was significantly reduced. This was particularly clear when the seedlings of the two sunflower cultivars were sprayed with ZnO NPs two days prior to planting the best suppression ranging from 100 to 53.12% in Euro flower cv. and from 95.31 to 54.68% in Flame cv. The reported findings in this study suggest that the application of the ZnO NPs together with current control approaches could improve the health of field grown sunflower crops and therefore the overall yield.

An assay on endophytic bacteria from corn and paddy to control damping-off of Rhizoctonia solani in corn seedling

In controlling Rhizoctonia solani a causal agent of damping-off to many important crops practical and chemical control are applied. However, these control are not successfully eliminate the disease. Furthermore, chemical application causes environmental problem, harm to human, and fungal resistance. Biological control of fungal disease has been developed. In this study four endophytic bacteria Bacillus sp. AJ02 and Xanthomonas sp. DJ01 isolated from healthy corn and Arthrobacter sp. AP01 and Bacillus sp. DP01 isolated from healthy paddy were employed to control corn seedling damping-off caused by R. solani. It was shown that all bacterial isolates inhibited R. solani growth with several hyphal decrements such as curved, petite, lytic, and swollen hyphae. Bacterial isolates were able to decrease corn seedling damping-off. One isolate Bacillus sp. DP01 reduced more ungrowth corn. Better performance including seedling height, seeding weight and dry weight, and leaf number was shown when the seedling was applied with bacterial isolates.

Biocontrol potential of Trichoderma asperellum mutants T39 and T45 and their growth promotion of poplar seedlings

This study investigates the biocontrol potential of Trichoderma asperellum mutants against Rhizoctonia solani, Alternaria alternata, and Fusarium oxysporum and growth promotion of Populus davidiana × P. alba var. pyramidalis (PdPap poplar) seedlings. A T-DNA insertion mutant library of T. asperellum was constructed using Agrobacterium tumefaciens-mediated transformation. Sixty-five positive transformants (T1–T65) were obtained. Growth rates of the mutants T39 and T45 were the same, 39.68% faster than the WT. In toxin tolerance tests, only T39 had greater tolerance to A. alternata fermentation broth than the WT, but mutant T45 had the same tolerance as the WT to all fermentation broths. Furthermore, T39 and T45 had a greater antagonistic ability than the WT strain against R. solani and A. alternata. The inhibition rate of the mutants T39 and T45 against A. alternata are 73.92% and 80.76%, respectively, and 63.51% and 63.74%, respectively. Furthermore, the three strains increased the activities of superoxide dismutases, peroxidase, catalase (CAT) and phenylalanine ammonia lyase (PAL) in PdPap seedling leaves. CAT and PAL activity in the PdPap seedling leaves was 11.25 and 5.50 times higher, respectively, in the presence of T39 than in the control group and 12 and 6.35 times higher, respectively, in the presence of T45 than in the control group. All three strains promoted seedling growth and the root and stem development, especially mutant T45. Mutants T39 and T45 reduced the incidence of pathogenic fungi in poplar and stimulated poplar seedling growth.

Atividade fungitóxica de extratos de Piper sp. contra os fungos Rhizoctonia solani e Sclerotium rolfsii

A busca por mecanismos que podem ajudar no controle de fitopatógenos tem sido recorrente, tendo como fonte a diversidade biológica, dada à sua variabilidade, fornecendo compostos com ação farmacológica diversa, tal qual no combate de microrganismos. Estudos relatam o uso de extratos contra os fungos fitopatogênicos com o objetivo de manter um equilíbrio destes patógenos, por estes causarem grandes danos em diversas culturas agrícolas. Por tanto este trabalho tem como objetivo testar extratos de Piper sp. contra os fungos Rhizoctonia solani e Sclerotium rolfsii, patógenos de extrema importância na cultura do feijoeiro. Desta forma, foram coletadas na casa de vegetação da Embrapa Rondônia, talos e folhas de Piper sp. e, após sua maceração, em solução extratora tampão PBS 0,1 M obteve-se os extratos, na proporção 1:10 (p/v, g/mL). Os extratos foram adicionados ao meio BDA semi-sólido na proporção 1/100 (V/V) sendo em seguida homogeneizados e vertidos em placas de petri. No centro das placas, discos de micélio dos patógenos foram depositados, sendo vedadas e incubadas em câmara B.O.D. por até 96h, sob condições controladas de temperatura e fotoperíodo de 12h. A atividade antifúngica dos extratos também foi avaliada em experimento in vivo, conduzido em casa de vegetação. Para tanto, plântulas de feijoeiro foram inoculadas com os patógenos e testadas com diferentes concentrações dos extratos de Piper sp. Foram avaliadas 6 concentrações, com 5 repetições por tratamento. Como controles foram usados tampão PBS 0,1 M e os fungicidas Amistar e Vitavax, conforme recomendação do fabricante. As avaliações foram realizadas diariamente, a partir do segundo dia de incubação, nas quais foram feitas as medições do halo de crescimento dos fungos, por meio de um paquímetro, até que a medição das placas que continham o grupo controle com PBS atingissem a borda das mesmas. Dos extratos testados, o extrato de talo promoveu inibição do crescimento de R. solani estatisticamente superior ao efeito do fungicida comercial, enquanto que contra S. rolfsii, embora o extrato tenha sido eficiente, o efeito foi inferior ao do fungicida testado. Este trabalho permite inferir que extratos de Piper sp. apresentaram atividades significativas contra os fungos Rhizoctonia solani e Sclerotium rolfsii. Novos testes serão realizados para verificar sua eficiência in vivo (campo).

Effect of compost tea containing phosphogypsum on potato plant growth and protection against Fusarium solani infection.

Three composts made of industrial wastes were prepared by mixing olive oil mill waste water (OMW), olive pomace, coffee grounds, and phosphogypsum (0, 10, and 30%). Potato plants (Solanum tuberosum) cultivated in a greenhouse were used to screen compost tea suppressive ability. All compost tea treatments inhibited Fusarium solani growth and improved plant growth and response to F. solani infection. The antagonistic effects of the different treatments were associated with a marked increase of the antioxidant enzymes and PR (pathogenesis related) protein expression and a decrease of disease severity. These results also showed that plant growth and disease suppression were improved by application of phosphogypsum-supplemented compost teas (A10 and A30). This enhancement can be attributed to the influence of phosphogypsum on nutrient elements and microbial diversity in the resulting compost teas.

Histone acetyltransferase TGF-1 regulates Trichoderma atroviride secondary metabolism and mycoparasitism.

Some filamentous fungi of the Trichoderma genus are used as biocontrol agents against airborne and soilborne phytopathogens. The proposed mechanism by which Trichoderma spp. antagonizes phytopathogens is through the release of lytic enzymes, antimicrobial compounds, mycoparasitism, and the induction of systemic disease-resistance in plants. Here we analyzed the role of TGF-1 (Trichoderma Gcn Five-1), a histone acetyltransferase of Trichoderma atroviride, in mycoparasitism and antibiosis against the phytopathogen Rhizoctonia solani. Trichostatin A (TSA), a histone deacetylase inhibitor that promotes histone acetylation, slightly affected T. atroviride and R. solani growth, but not the growth of the mycoparasite over R. solani. Application of TSA to the liquid medium induced synthesis of antimicrobial compounds. Expression analysis of the mycoparasitism-related genes ech-42 and prb-1, which encode an endochitinase and a proteinase, as well as the secondary metabolism-related genes pbs-1 and tps-1, which encode a peptaibol synthetase and a terpene synthase, respectively, showed that they were regulated by TSA. A T. atroviride strain harboring a deletion of tgf-1 gene showed slow growth, thinner and less branched hyphae than the wild-type strain, whereas its ability to coil around the R. solani hyphae was not affected. Δtgf-1 presented a diminished capacity to grow over R. solani, but the ability of its mycelium -free culture filtrates (MFCF) to inhibit the phytopathogen growth was enhanced. Intriguingly, addition of TSA to the culture medium reverted the enhanced inhibition growth of Δtgf-1 MFCF on R. solani at levels compared to the wild-type MFCF grown in medium amended with TSA. The presence of R. solani mycelium in the culture medium induced similar proteinase activity in a Δtgf-1 compared to the wild-type, whereas the chitinolytic activity was higher in a Δtgf-1 mutant in the absence of R. solani, compared to the parental strain. Expression of mycoparasitism- and secondary metabolism-related genes in Δtgf-1 was differentially regulated in the presence or absence of R. solani. These results indicate that histone acetylation may play important roles in the biocontrol mechanisms of T. atroviride.

Effect of biofumigation by Calligonum polygonoides, dry olive leaves, and ash of olive leaves on chilli pepper growth and recovery of Rhizoctonia solani

Rhizoctonia solani J.G. Kühn is a serious soilborne pathogen in chilli fields worldwide. This study examined the effect of biofumigation using arta (Calligonum polygonoides L.) and olive (Olea europaea L.) plant material on chilli growth and recovery of R. solani from chilli plants. The experiment was conducted under greenhouse conditions in potted soil amended with no plant material (control) or with plant material from Calligonum and Olea (olive leaves, or ash of olive leaves). Chilli was planted in the amended soils and inoculated with R. solani. Plant height, number of fruits , and frequency of recovery of R. solani from chilli were recorded. Soil amendment with Calligonum plant material resulted in the lowest frequency of recovery of R. solani. Moreover, Calligonum treatment increased dry mass and height of chilli plants compared to other treatments. Also, treatment with olive plant parts inhibited R. solani growth and enhanced growth of chilli compared to the control treatment. Thus, C. polygonoides and O. europaea are potental biofumigant plants to control R. solani.

In vitro and in vivo Assay for Assessment of the Biological Control Potential of Streptomyces sp. KT

Rhizoctonia solani is fungal plant pathogen that infects many different host plants. Recently, biological control agents that are friendly to the environment and ecosystems have attracted much attention as an alternative to the use of chemical fungicide which have been used worldwide to control soil borne pathogens including R. solani. In this study, 53 strains of actinomycetes isolated from environmental soils, and antifungal activities of them were assessed by the dual culture assay. Strain KT showed strong inhibitory activities against 8 phytopathogenic fungi. A great suppressive effect on R. solani growth was observed in the inoculation test of plants using cucumber and chin-geng-sai. In addition, infection of Bipolaris oryzae also could be suppressed in the detached leaf assay using oats. As a result of genetic analysis, it was shown that KT was a species closely related to Streptomyces lavenduligriseus NRRL B-3173T. However, as far as we know, there is no report for biological control agents using S. lavenduligriseus. This study suggests that the strain KT may useful as biological control agents to suppress various crop diseases.