Root Rot Of Cucumber Research Articles

Effectiveness of Selected Biological Agents, Chemical Inducers, and Fungicides in Managing Cucumber Root Rot Disease caused by Rhizoctonia solani

Effectiveness of Selected Biological Agents, Chemical Inducers, and Fungicides in Managing Cucumber Root Rot Disease caused by Rhizoctonia solani

Are formae speciales pathogens really host specific? A broadened host specificity in Fusarium oxysporum f.sp. radicis-cucumerinum.

Phytopathogenic strains of Fusarium oxysporum Schlecht exhibit clear host specificity, which appears to be a persistent characteristic and a dependable base for the forma specialis system of these pathogens. Here, we report an altered host specificity of the F. oxysporum f.sp. radicis-cucumerinum strain V03-2g (Forc V03-2g) - a causative agent of cucumber root-rot, the clonal derivates of which acquired the ability to infect tomato plants. Since the clonal derivates of Forc V03-2g with transformed host specificity preserved their ability to parasitize on cucumber plants, the changes that occurred can be classified as broadening of host specificity. To our knowledge, this is the first observation of pathogenicity changes in formae speciales of F. oxysporum. The clonal derivates acquired could be used to trace genetic determinants of the host specificity of phytopathogenic strains of F. oxysporum.

Combining multiple Bacillus spp. with fish protein hydrolysates mitigates root rot (Fusarium solani) and improves cucumber seedlings growth and substrate nutrients.

The effect of Bacillus strains combined with fish protein hydrolysates (FPHs) on cucumber root rot disease, seedlings growth and substrate nutrients was investigated. We isolated three strains capable of mitigating cucumber root rot disease, XY-1 and XY-13strains were identified as B. amyloliquefaciens, and XY-53strain as B. subtilis. In the absence of bacteria, The 200×dilution (5mlL-1 ) of FPHs was the optimum concentration for improving cucumber seedlings growth. In vivo antibiosis tests showed that combined bacteria alongside FPHs inhibited the pathogen growth by 85%~90%, higher than individual bacteria. The FPHs combined either with XY-1 and XY-53strains or with XY-13 and XY-53strains promoted seedlings growth under infection, whereas FPHs combined with a mixture of XY-1, XY-13 and XY-53strains showed the highest total phosphorus and organic matter content in substrate. Moreover, FPHs combined with XY-53strain increased urease activity, while combined either with XY-13 and XY-53strains or with XY-1, XY-13 and XY-53strains increased sucrase activity under infection. FPHs combined with B. amyloliquefaciens and B. subtilis had great potential to suppress growth of root rot and promote cucumber seedlings and increase substrate nutrient content. Co-inoculation of B. amyloliquefaciens and B. subtilis with addition of FPHs is a good strategy for maintaining healthy crops.

First report of Fusarium equiseti causing crown and root rot of cucumber in India

First report of Fusarium equiseti causing crown and root rot of cucumber in India

A novel salt-tolerant strain Trichoderma atroviride HN082102.1 isolated from marine habitat alleviates salt stress and diminishes cucumber root rot caused by Fusarium oxysporum

BackgroundSalt stress threaten the growth of plants, and even aggravate plant disease. In this article, salt-tolerant Trichoderma strain was isolated, and its potential to alleviate salt stress and diminish cucumber root rot caused by Fusarium oxysporum was evaluated.ResultsTwenty-seven Trichoderma isolates were isolated from samples of sea muds and algae collected from the South Sea of China. Among these, the isolate HN082102.1 showed the most excellent salt tolerance and antagonistic activity against F. oxysporum causing root rot in cucumber and was identified as T. atroviride. Its antagonism ability may be due to mycoparasitism and inhibition effect of volatile substances. The application of Trichoderma mitigated the adverse effects of salt stress and promoted the growth of cucumber under 100 mM and 200 mM NaCl, especially for the root. When T. atroviride HN082102.1 was applied, root fresh weights increased by 92.55 and 84.86%, respectively, and root dry weights increased by 75.71 and 53.31%, respectively. Meanwhile, the application of HN082102.1 reduced the disease index of cucumber root rot by 63.64 and 71.01% under 100- and 0-mM saline conditions, respectively, indicating that this isolate could inhibit cucumber root rot under salt stress.ConclusionsThis is the first report of salt-tolerant T. atroviride isolated from marine habitat showing antagonistic activity to F. oxysporum, and the results provide evidence for the novel strain T. atroviride HN082102.1 in alleviating salt stress and diminishing cucumber root rot, indicating that T. atroviride strain HN082102.1 can be used as biological control agent in saline alkali land.

Biological control of fungi associated with damping-off and root rot disease of cucumber (Cucumis sativus L.)

Damping-off and root rot is a serious disease infecting cucumber on both seedling and adult stages. In this study, fifty-six fungal isolates were restored from cucumber plants showing typical symptoms of damping-off and root rot disease growing in different fields in Assiut governorate. These isolates were Pythium aphanidermatum (8 isolates), F. solani (12 isolates), Rhizoctonia solani (10 isolates), Drechslera halodes (12 isolates) and Macrophomina phaseolina (14 isolates). Pathogenicity tests revealed that these isolates were able to cause damping-off and root rot disease, however the most severe isolates were M. phaseolina isolate No 3 followed by R. solani No. 4, then F. solani isolate No. 6 as they caused root rot severity about 92.75, 91.5 and 76.75% respectively. In this study application of Gliocladium catenulatum, and Trichoderma harzianum proved to be an efficient antagonist to inhibit mycelial growth of plant pathogenic fungi in vitro, and to reduce the disease severity under greenhouse conditions, and significantly reduced the pre- and post-emergence damping off and root rot severity by rate of 50, 43.5, 52.33%, respectively in case of G. catenulatum and 60, 51.5, 53.32% in case of T. harzianum. These results proved that application of T. harzainum or G. catenulatum is an efficient method to control the causal pathogens of damping-off and root rot of cucumber.

First report of garden cucumber root rot caused by Globisporangium ultimum var. ultimum in Kyrgyzstan

First report of garden cucumber root rot caused by Globisporangium ultimum var. ultimum in Kyrgyzstan

Soil incorporation of buckwheat as a pre-plant amendment provides control of Rhizoctonia damping-off and root rot of radish and Pythium damping-off and root rot of cucumber

Buckwheat is a rapidly growing cover crop with the potential to improve soil quality and health. In this study, the impact of buckwheat plant material (BPM) as a soil amendment on seedling emergence and suppression of damping-off and root rot of radish (Rhizoctonia solani) and cucumber (Pythium ultimum) was investigated in pot assays. Fresh BPM grown in a greenhouse potting mix for 4 weeks was chopped in small 1–2 cm long pieces and incorporated into field soil containing 0–10% of R. solani or P. ultimum inoculum produced on sterilized rye seed. The infested soil was then incubated for 0–8 weeks prior to planting radish or cucumber seed. The effects of BPM on plant growth and disease development were determined 2 weeks after planting. There was no disease protection if radish and cucumber seeds were planted within 1–2 weeks after soil incorporation of BPM. Disease protection was evident when planting was delayed for 3 weeks after BPM amendment to soil. BPM soil amendment provided protection of radish plants from Rhizoctonia damping-off and protection of cucumber plants from Pythium damping-off and root rot. BPM amendments had no effect on promoting plant growth but slightly increased soil pH. In amended soil receiving 4% and 10% of BPM planted with radish or cucumber seeds 0, 3 and 8 weeks later, total populations of indigenous fungi were 0.66–2.01 log units higher and bacteria were 0.53–0.92 log units higher compared with the populations in the non-amended soils. Buckwheat soil amendment offers a potential option to improve plant and soil health.

Phomopsis Black Root Rot of Cucumber in Washington State Caused by Diaporthe sclerotioides

Phomopsis black root rot of cucumber (Cucumis sativus L.), caused by Diaporthe sclerotioides (syn. Phomopsis sclerotioides), has been reported in Austria, Britain, Canada, Denmark, France, Germany, Italy, Japan, Malaysia, the Netherlands, and Norway (Shishido et al. 2016). In August 2017, wilted plants were observed in patches comprising 10% of a 5-ha organic cucumber crop in Skagit Co., WA, after fruit had formed. Crowns, tap roots, and secondary roots had pink to brown, dry, corky lesions, black pseudostromata, and rectangular pseudosclerotia within cortical cells. Sections of symptomatic roots and crowns (≤10 mm long) of eight plants selected randomly were surface-sterilized in 0.6% NaOCl for 3 to 5 min, triple-rinsed in sterilized water, dried on sterilized blotters, plated on water agar, and incubated at 24 ± 2°C with a natural day/night cycle. Hyphae were transferred to 1/2-strength PDA amended with chloramphenicol (100 ppm). After 2 weeks, each isolate covered the plate with gray-brown, dense mycelium. Flat, brown-black, irregular pseudostromata formed in the medium. Five isolates were grown in 1/2-strength potato dextrose broth on a shaker for 7 days, mycelia harvested, DNA extracted, and the internal transcribed spacer (ITS) 1-5.8S-ITS2 region of ribosomal DNA amplified using universal eukaryotic primers UN-UP18S42 and UN-LO28S576B (Schroeder et al. 2006). The sequences of isolates Dsl004, Dsl005, Dsl006, and Dsl008 (GenBank accession nos. MG434673.1, MG434674.1, MG434675.1, and MG434676.1, respectively) had 100% identity to that of a D. sclerotioides isolate (NR_111069.1); the sequence of Dsl002 (MG434672.1) had 99% identity because of a 7-nt insertion in the ITS1 region. All five isolates and DNA of D. sclerotioides ATCC18585 (ex-type culture) produced the expected 392-bp band of amplified DNA from the ITS rDNA using the highly specific primers CPs-1 and CPs-2 (Shishido et al. 2010). In addition, a 566-nt consensus sequence of the TEF 1-α gene of Dsl002, Dsl004 to Dsl006, and Dsl008 (MG868937) generated by PCR assay with primers EF-2F and EF-5AR (Taskin et al. 2010) was 100% identical to that of D. sclerotioides ATCC18585 (MG868936). Pathogenicity of the five isolates on cucumber was verified in a greenhouse using two methods, direct-seeding and transplanting. Two-week-old colonized PDA plates of each isolate were cut into 3 mm³ pieces and mixed in Sunshine Potting Mix #1 (Sungro Horticulture, Canada) (half a plate/1.0 liter potting mix/15-cm-diameter pot). A nontreated seed (cv. Turbo) was then planted in the medium in each of five replicate pots/isolate, and a 10-day-old Turbo seedling was transplanted into each of five replicate pots/isolate. For the control treatment, potting medium was amended with noncolonized PDA (five direct-seeded and five transplanted replicates). Plants were maintained at 18 to 26°C with 10 h light/day. Dsl004, Dsl005, Dsl006, and Dsl008 caused wilting and death of plants in 3 weeks with the direct-seeding method, and in 4 to 5 weeks for the transplanting method. Dsl002 caused stunting and minor wilting. Control plants remained healthy. The roots of inoculated plants had corky lesions with pseudostromata and pseudosclerotia. D. sclerotioides was reisolated from roots of inoculated plants but not control plants. The species was confirmed morphologically and by ITS rDNA and TEF 1-α sequencing. This is the first report of Phomopsis black root rot of cucumber caused by D. sclerotioides in Washington State or anywhere in the U.S.A. The disease was reported in greenhouse cucumber in neighboring British Columbia, Canada, in 1972 (Ormrod and Christie 1972). Research is needed to assess prevalence of the pathogen and management strategies to limit spread of the disease.

Effect of Soil Inoculum Density and Temperature on the Incidence of Cucumber Black Root Rot.

The effects of the density of Phomopsis sclerotioides in soil and other environmental factors on black root rot of cucumber were investigated. Cucumber plants were grown in soil containing P. sclerotioides at 1, 10, 100, and 1000 CFU/g. Wilt incidence from 3 to 7 weeks after transplanting was strongly correlated with P. sclerotioides density in soil (P < 0.05). Root rot of squash rootstock occurred in soil with very low inoculum densities (0.1 CFU/g), and was strongly related to P. sclerotioides density (Y = -0.3x + 1.2, R2 = 0.743, P < 0.05) at 8 weeks after transplanting. Cucumber plants showed wilt symptoms in soil containing 1 CFU/g. Wilt symptoms in cucumber plants occurred 4 to 7 days earlier in soil at 22°C than in soil at 27 or 17°C. Root rot development could be predicted from the density of P. sclerotioides in soil and soil temperature. However, further studies on the effects of other environmental factors are required to test the linear model in commercial fields. This information is essential for determining the threshold pathogen density at which most control techniques, particularly those other than soil disinfection, will be effective.

Characterisation of antagonistic Bacillus and Pseudomonas strains for biocontrol potential and suppression of damping‐off and root rot diseases

AbstractNovel strains of rhizobacteria, Pseudomonas fluorescens Pf 9A‐14, Pseudomonas sp. Psp. 8D‐45 and Bacillus subtilis Bs 8B‐1, showed broad‐spectrum antagonistic activity and provided suppression of Pythium damping‐off and root rot of cucumber. Their biocontrol potential was further investigated for suppression of additional seedling diseases of cucumber (Phytophthora capsici) and radish (Rhizoctonia solani). Bacterial strains were also characterised for production of antibiotics, metabolites, volatiles, phytohormones and lytic enzymes. Seed and pre‐plant applications of all three antagonistic bacteria as cell suspension and talc or irradiated peat formulations to the infested potting mix provided overall high level of suppression of Phytophthora damping‐off and root rot of cucumber (66–85% healthy seedlings) and relatively low level of suppression of Rhizoctonia damping‐off of radish (18–38% healthy seedlings). Bacterial treatments also resulted in higher plant fresh masses. Seed coating with irradiated peat formulation of a mixture of three bacteria resulted in superior control of Phytophthora damping‐off and root rot of cucumber and much higher plant fresh masses. The presence of genes for biosynthesis of phenazine‐1‐carboxylic acid, 2,4‐diacetylphloroglucinol, pyrrolnitrin and pyoluteorin was confirmed in Pseudomonas strains, and that of fengycin, bacillomycin, bacilysin, surfactin and iturin A in B. subtilis Bs 8B‐1. All three strains produced HCN, salicylic acid, indole‐3‐acetic acid, protease and β‐1,3‐glucanase. Both Pseudomonas strains produced siderophores and only P. fluorescens Pf 9A‐14 showed phosphate solubilisation and chitinase activity. All three strains inhibited pathogen growth by producing volatiles, and gas chromatography–mass spectrometry analysis revealed eight compounds in Pf 9A‐14, 10 in Bs 8B‐1 and 4 in Psp 8D‐45, some with known antifungal activity. The antagonistic and plant‐growth promotion activities of these strains might be due to production of antibiotics, metabolites, lytic enzymes or phytohormones.

寡雄腐霉发酵液对番茄生长的影响及对灰霉病的防治作用

PDF HTML阅读 XML下载 导出引用 引用提醒 寡雄腐霉发酵液对番茄生长的影响及对灰霉病的防治作用 DOI: 10.5846/stxb201303070373 作者: 作者单位: 西南大学资源环境学院,西南大学资源环境学院,西南大学资源环境学院,西南大学资源环境学院,四川省凉山州烟草公司,四川省凉山州烟草公司 作者简介: 通讯作者: 中图分类号: 基金项目: 国家973重大基础研究项目(2013CB127405);四川省凉山州烟草公司科技攻关项目(2012-12);云南省烟草公司科技项目(2013YN11);国家烟草专卖(11020130216) Influence of the fermentation broth of Pythium oligandrum on the growth and botrytis control of tomato seedlings Author: Affiliation: College of Resource and Environment,Southwest University,College of Resource and Environment,Southwest University;China;Sichuan Tobacco Corporation Liangshanzhou Branch;China,College of Resource and Environment,Southwest University,,Sichuan Tobacco Corporation Liangshanzhou Branch,Sichuan Tobacco Corporation Liangshanzhou Branch Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了研发对番茄灰霉病高效、稳定、安全的生物农药,试验利用自主分离获得的寡雄腐霉菌株制备发酵液,采用盆栽试验研究寡雄腐霉发酵液对番茄生长的影响和对灰霉病的防治效果及机制,并在大田生产中验证其生防效果。结果表明,盆栽试验中,寡雄腐霉发酵液促进健康番茄植株生长,植株总生物量和根系生物量分别增加9.5%和15.4%,提高了植株叶绿素含量、根系活力及氮、磷、钾吸收量,并使带病番茄植株的发病率和病情指数分别降低57.2%和60.3%,相对防治效果达60.3%,施用寡雄腐霉发酵液对番茄叶片细胞膜具有保护性,降低丙二醛含量,提高病原性相关酶——超氧化物歧化酶、多酚氧化酶和苯丙氨酸解氨酶活性。后续田间试验中寡雄腐霉发酵液对番茄灰霉病的防治效果达71.2%。说明寡雄腐霉发酵液能有效防治番茄灰霉病,还具有促进番茄生长的作用,并且可诱导番茄植株对病原菌的防御作用,应用前景广泛。 Abstract:Grey mold (Botrytis cinerea Pers.) is a pathogenic fungus of tomato botrytis, which occurs seriously in continuous cropping soil and causes heavily economic losses in tomato production. Farmers have to grow tomato annually in the same soil since lack of soil resources in China. Chemicals such as carbendazim, thiophanate-methyl and benlate have been used to control tomato botrytis for decades and a large amount of these chemicals have thus remained in both tomato fruits and soils, which is harmful to both human being and the environment. On the other hand, the pathogenic Botrytis cinerea has also developed resistance to these chemicals. As a result, an increasing attention has been paid to develop safe, effective, and stable bio-agents to control tomato botrytis in recent years. Studies have reported that Pythium oligandrum could inhibit or kill plant pathogenic fungi, including Botrytis cinerea, Phytophthora nicotiana and Pythium aphanidermatum. The oospores of P. oligandrum have been hence used to control black shank disease of tobacco, grey mold of tomato, and root rot of cucumber. However, the bio-control effect of the oospore agent is unstable and unsatisfactory because their germination and hyphal growth are significantly influenced by temperature, humidity, sun light, soil types, rainfall, and agricultural measurements. To address the importance of metabolites produced by P. oligandrum in bio-controlling of plant fungal diseases, in both greenhouse and field experiments we tested the hypothesis that P. oligandrum fermentation broth could influence the growth and botrytis control of tomato. For the greenhouse pot experiment, four treatments had been examined: plants inoculated or not inoculated with pathogen plus culture solution or plus fermentation broth. Meanwhile, tomato seedlings were respectively sprayed with water (control), fermentation broth or culture solution, before the occurrence of botrytis in the field. In the greenhouse pot experiment, the fermentation broth promoted the growth of tomato seedlings and total plant biomass production by 9.5% and root biomass by 15.4% compared to the control (pathogen inoculation plus culture solution). Chlorophyll concentrations in the leaves, root activities, and nutrient absorption (nitrogen, phosphorus, and potassium) in the field seedlings were also increased by spraying the fermentation broth. Meanwhile, the disease incidence was reduced by 57.2% and disease index by 60.3% with the fermentation broth supply under pathogen inoculation, leading to 60.3% of the relative control efficacy. Further results showed that the fermentation broth could protect the cell membrane of leaves against the pathogen damage, since less malondialdehyde, one of the oxidative products of cell lipids, was detected. In addition, the fermentation broth stimulated enzyme activities related to plant disease resistance such as superoxide dismutase, polyphenol oxidase, and phenylalanine ammonialyase in the leaves of tomato seedlings. The relative control efficacy of the fermentation broth reached 71.2% in the filed tomato seedlings. In summary, the fermentation broth of P. oligandrum have multiple functions, including the induction of the resistance to grey mold, the decrease in botrytis occurrence, and the promotion of plant growth, which are different from other bio-control agents that can control diseases only. Our research showed the potential of the metabolites produced by P. oligandrum as an effective, stable and safe bio-control agent. Further investigations are needed to clarify the effectiveness of metabolites from P. oligandrum in disease control. 参考文献 相似文献 引证文献

Isolation, characterization, and formulation of antagonistic bacteria for the management of seedlings damping-off and root rot disease of cucumber

Antagonistic bacteria are common soil inhabitants with potential to be developed into biofungicides for the management of seedling damping-off, root rot, and other soil-borne diseases of various crops. In this study, antagonistic bacteria were isolated from a commercial potato field and screened for their growth inhibition of fungal and oomycete pathogens in laboratory tests. The biocontrol potential of the 3 most effective antagonistic bacteria from the in vitro tests was evaluated against seedling damping-off and root rot of cucumber caused by Pythium ultimum. Based on phenotypic characteristics, biochemical tests, and sequence analysis of 16S-23S rDNA gene, the 3 antagonistic bacteria were identified as Pseudomonas fluorescens (isolate 9A-14), Pseudomonas sp. (isolate 8D-45), and Bacillus subtilis (isolate 8B-1). All 3 bacteria promoted plant growth and suppressed Pythium damping-off and root rot of cucumber seedlings in growth-room assays. Both pre- and post-planting application of these bacteria to an infested peat mix significantly increased plant fresh masses by 113%-184% and percentage of healthy seedlings by 100%-290%, and decreased damping-off and root rot severity by 27%-50%. The peat and talc formulations of these antagonistic bacteria applied as seed or amendment treatments to the infested peat mix effectively controlled Pythium damping-off and root rot of cucumber seedlings and enhanced plant growth. The survival of all 3 antagonistic bacteria in peat and talc formulations decreased over time at room temperature, but the populations remained above 10(8) CFU/g during the 180-day storage period. The peat formulation of a mixture of 3 bacteria was the best seed treatment, significantly increasing the plant fresh masses by 245% as compared with the Pythium control, and by 61.4% as compared with the noninfested control. This study suggests that the indigenous bacteria from agricultural soils can be developed and formulated as biofungicides for minimizing the early crop losses caused by seedling damping-off and root rot diseases.

Using Commercial Compost as Control Measures against Cucumber Root-Rot Disease

Five commercial composts were evaluated to suppress the root-rot pathogens (Fusarium solani (Mart.) App. and Wr, Pythium ultimum Trow, Rhizoctonia solani Kuhn, and Sclerotium rolfsii Sacc.) of cucumber plants under in vitro and greenhouse conditions. In vitro tests showed that all tested unautoclaved and unfiltrated composts water extracts (CWEs) had inhibitor effect against pathogenic fungi, compared to autoclaved and filtrated ones. Also, the inhibitor effects of 40 bacteria and 15 fungi isolated from composts were tested against the mycelial growth of cucumber root-rot pathogens. Twenty two bacteria and twelve fungal isolates had antagonistic effect against root-rot pathogens. The antagonistic fungal isolates were identified as 6 isolates belong to the genus Aspergillus spp., 5 isolates belong to the genus Penicillium spp. and one isolate belong to the genus Chaetomium spp. Under greenhouse conditions, the obtained results in pot experiment using artificial infested soil with cucumber root-rot pathogens showed that the compost amended soil reduced the percentage of disease incidence, pathogenic fungi population, and improved the cucumber vegetative parameters as shoot length, root length, fresh weight, and dry weight. These results suggested that composts are consequently considered as control measure against cucumber root-rot pathogens.

Continuous Effects of Reductive Soil Disinfection on Black Root Rot of Cucumber

Continuous Effects of Reductive Soil Disinfection on Black Root Rot of Cucumber

Plant Growth Promoting Rhizobacteria (PGPR) Induce Cucumber Root-Rot Protection under Plastic Tunnels Conditions

Eighteen isolates of plant growth promoting rhizobacteria (PGPR) were isolated from samples of four crops grown in reclaimed fields at Nobariya district (Behera Governorate). The isolates were in vitro tested for their antagonistic effect against the three fungal pathogens causing root-rot of cucumber, i.e. Fusarium solani, Pythium ultimum and Rhizoctonia solani, as well as its effect on plant growth. Nine isolates showed moderate to strong inhibition at least to one of these pathogens and increased vigour index of cucumber. Selected isolates were tested for production of indole acetic acid (IAA) and phosphorous solubilisation capability. The biocontrol ability of these antagonistic isolates was evaluated using an in vivo assay. Accordingly, three isolates were selected and used for soil treatment to control root-rot of cucumber in pot experiments. Bacterial isolates mixtures induced significant protection were the same as the individual isolates that significantly reduced symptoms of root-rot pathogens individual or its mixture in pot experiment. Pseudomonas fluorescens (P-11), P. fluorescens (Cu-2) and Bacillus subtilis (Cu-4) were effective for controlling root-rot disease, under plastic tunnels condition. Mixture of the three isolates was most effective to decrease percentage of root-rot and disease severity compared with other treatment and untreated treatment. Seeds treated with P. fluorescens (P-11), P. fluorescens (Cu-2) and B. subtilis (Cu-4) isolates and challenge inoculated with mixture of P. ultimum, F. solani and R. solani significantly reduced disease compared with check treatment and induced the plants to synthesize peroxidase and chitinase enzymes. The maximum phenolic content was observed in P. fluorescens (P-11) and P. fluorescens (Cu-2) pretreated plants and challenge inoculated with the pathogens, and the higher amounts of phenolics were noticed even on 10th day after the pathogens challenge inoculation.

The efficiency of two new formulated biofungicides in the control of damping-off and root rot of cucumber and improving the plant defence system

The ability of Rhizoleen-T and Rhizoleen-B to suppress the roots’ diseases of cucumber caused by Fusarium oxysporum and Rhizoctonia solani and induction of the plant defence system was evaluated. The results showed a significant suppression in damping-off and root rot of cucumber when the two biofungicides were applied. They increased the surviving percentage of the treated plants to 98.0% and reduced the mean disease rating to 1.0. The biofungicides significantly enhanced the plant’s morphology and physiology when compared with either infected or non-infected control. The mechanism of action of the biofungicides is could be through the enhancement of the plant defences, in addition to their antifungal effect. They stimulated the defence of the plants by increasing the content of proline and phenols and induction the defensin genes. Biofungicides induced defence genes in the 50-day-old treated plants. The biofungicides are effective, cost effective and applicable in the control of root diseases of cucumber.

Antagonistic Potential of Fluorescent Pseudomonads and Control of Crown and Root Rot of Cucumber Caused by Phythophtora drechsleri

In this study, 200 isolates of fluorescent pseudomonads were isolated from different fields of East and West Azarbaijan and Ardebil provinces of Iran. These bacterial isolates were screened on the basis of a dual culture assay, the presence of known antibiotic genes, and their ability to successfully colonize roots and to promote plant growth. Twelve isolates exhibited 30% or more inhibition of mycelia growth of . Genes encoding production of the antibiotics 2,4-diacetylphloroglucinol, phenazine-1-carboxylic acid, and pyoluteorin were detected in some strains but none of the strains possessed the coding gene for production of antibiotic pyrrolnitrin. In an test for root colonization, the population density on roots of plants treated with most of the above strains was more than 6 CFU roots, with a maximum of 7.99 CFU roots for strain 58A. Most of the strains promoted significant plant growth in comparison to non-treated controls. In green house studies, the percentage of healthy plants in pots treated with strains 58A and 8B was 90.8% and 88.7%, respectively. The difference between these treatments and treatment with the fungicide metalaxyl was not significant.

Inhibitory effect of some plant crude extracts against cucumber damping-off agents

This study was aimed to investigate the antifungal effect of the crude extracts derived from 37 Iranian plant species against Phytophthora melonis and Pythium aphanidermatum, the causal agents of cucumber root rot and damping off. The crude extracts were obtained using three different solvents; ethanol, methanol and water. The inhibitory effect of these extracts was examined based on the paper disc diffusion method (5 mg per paper disc) with four replications. The ethanolic extract of Acroptilon repens, that showed a remarkable inhibitory effect on the tested oomycetes was selected for further examination. To determine the most effective component, the ethanolic extract of A. repens was fractionated by thin layer chromatography (TLC) and each fraction was tested for the antifungal activity. The potential of the ethanolic extract of A. repens in the control of cucumber damping off agents was evaluated in a completely randomized design with eight replications, under greenhouse conditions. Based on the results obtained from the screening of TLC fractions, it was found that a fraction with Rf value equal to 0.89 had the most inhibitory effect against the tested oomycetes. Greenhouse experiment showed that the soil treatment by the ethanolic extract of A. repens at all the selected concentrations (0.2, 0.4 and 0.6 g per plastic pot) were significantly effective in reducing the disease incidence caused by P. melonis compared to the control. Moreover, seed treatment by 10% w/w of ethanolic extract of A. repens significantly suppressed damping off symptom caused by P. aphanidermatum, when compared to the control.

Effectiveness of AG3 phosphonate formulation in suppressing phytophthora blight in cucumber and bell pepper plants under growth room conditions

Phytophthora blight or crown or root rot (Phytophthora capsici Leonian) is an important disease of a wide range of plant species including peppers, tomatoes, cucumbers and other cucurbits in Canada and worldwide. We have previously demonstrated the effectiveness of a new liquid formulation of AG3 phosphonate (Calirus 150, Bromine Compounds Ltd., Beer Sheva, Israel) in suppressing pythium damping-off of cucumbers and clubroot of bok choy and cabbage. In this study, the effectiveness of AG3 phosphonate formulation to suppress phytophthora damping-off and root rot of cucumber (Cucumis sativus L.) seedlings or phytophthora blight of bell pepper (Capsicum annuum L.) plants was determined in a peat-based mix or sandy-loam soil artificially infested with soil inoculum of P. capsici under growth room conditions. In an infested peat-based mix, AG3 phosphonate preplanting amendment or postplanting drench treatments (0.05%, 0.1% and 0.2% a.i.) and a 10-min seed-soak treatment (10.45% a.i.) significantly increased the percentage of healthy cucumber seedlings and reduced damping-off and root rot severity. The seed-soak and 0.2% treatments were the most effective treatments that consistently suppressed damping-off and root rot of cucumber even in a peat-based mix infested with high inoculum levels of P. capsici. Disease severity on cucumber plants was also significantly less in the AG3 phosphonate treatments. The single drench applications of AG3 phosphonate (0.05%, 0.1% and 0.2% a.i.) significantly reduced the incidence and severity of phytophthora blight of bell pepper plants in an infested peat-based mix or a sandy-loam soil compared with the control plants receiving no treatment. The best control of phytophthora blight of bell pepper was achieved with the higher rate (0.2% a.i.) in both peat-based mix and soil with 90% of the plants remaining healthy compared with none in the control. The disease protection increased with increasing concentrations of AG3 phosphonate in both bell peppers and cucumbers without any phytotoxicity.