Effect of mycoparasitic fungi on the development of Sphaerotheca fusca in melon leaves

doi:10.1017/S0953756202006974

Mycological Research

Volume 107, Issue 1, January 2003, Pages 64-71

https://doi.org/10.1017/S0953756202006974 Get rights and content

We evaluated the possibilities of exploitation of several mycoparasitic fungi in the biocontrol of cucurbit powdery mildew (Sphaerotheca fusca) in melon greenhouses. To simplify the screening, an in vitro biological control test on detached leaves of melon has been used and a detailed microscopic analysis of the interactions between mycoparasites and S. fusca conducted. In this context, the effect of mycoparasitic fungi on the formation of infection structures of S. fusca such as haustoria, conidia and conidiospores has been quantified. On the basis of the microscopic data, effect of mycoparasites on severity and incidence of cucurbit powdery mildew has been discussed. Our results show that, under controlled environmental conditions, Acremonium alternatum, Ampelomyces quisqualis and especially Lecanicillium lecanii when applied in early stages of infection, were able to significantly reduce cucurbit powdery mildew symptoms and S. fusca development on melon leaves. These results indicate that these mycoparasites are promising candidates for the biocontrol of cucurbit powdery mildew in melon greenhouses.

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The mycoparasite restricts the number of P. xanthii haustoria, whereby the nutrient uptake of the pathogen is reduced. A. quisqualis also reduces disease multiplication due to the limitation of the number of powdery mildew conidiophores and conidia (Romero et al., 2003). The growth of the fungus A. quisqualis is considered to be slow (Kiss et al., 2004), and although the formation of pycnidia on culture media is possible, the conidiation is relatively poor (Angeli, 2013).
Ampelomyces quisqualis has been reported to be a promising biocontrol agent (BCA) against powdery mildew, and it has been commercialised as AQ10 Biofungicide®. However, isolated strains showed inconsistent results when applied under practical conditions, and research to find a thoroughly effective strain is still in progress. In addition, asexual spores of the BCA are required to parasitise powdery mildew; however, producing a high amount of conidia is difficult. The present study aimed to select of an effective strain of A. quisqualis against powdery mildew on zucchini leaves and to test its conidiation in liquid media. The efficacy of several isolates from cucurbits were tested and the most effective was identified as A. quisqualis CPA-9, which reduced powdery mildew on zucchini leaves up to 61.5 % when it was applied at 2.5 × 10⁵ conidia/mL. Conidial production of CPA-9 in liquid media was optimised, and several growing conditions were tested, such as the medium, agitation, and incubation time. Asexual reproduction was induced by modifying the a_w of the media or reducing agitation. A concentration of 7.3 × 10⁷ conidia/mL was achieved in 500-mL Erlenmeyer flasks containing 75 mL of potato dextrose broth modified with 2.5 % (w/v) of glycerol incubated at 25 °C for 11 days in the dark and without agitation. The produced conidia of CPA-9 maintained the biocontrol efficacy against P. xanthii on zucchini plants and reduced the disease incidence by up to 83 %.
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Ampelomyces is an ecologically and economically important pycnidial hyperparasite on powdery mildew disease which is distributed widely across the world. Ampelomyces, which are antagonistic to various powdery mildew fungi, have been studied by many researchers and rapidly replacing chemical control agents as they are highly specific, ecofriendly, and cost effective. The early stage of mycoparasitism is apparently biotrophic, but the invaded cytoplasm then begins to die, and a necrotrophic interaction occurs. Ampelomyces fungus represents a stress factor in the life cycle of the powdery mildew fungus which directly destructs the cytoplasm without producing any toxins and inhibits the sporulation. Therefore, the role of Ampelomyces in the natural control of powdery mildew fungi requires elaborate research. In this review, we have highlighted the taxonomy, diversity, hyperparasitism, and commercial application and its significance of Ampelomyces in agricultural ecosystems for research opportunities in the biocontrol of powdery mildew.
Identification and utilization of a new Erysiphe necator isolate NAFU1 to quickly evaluate powdery mildew resistance in wild Chinese grapevine species using detached leaves
2016, Plant Physiology and Biochemistry
Citation Excerpt :
Some apple powdery mildew isolates have also been maintained on the shoots of a highly susceptible apple cultivar in vitro (Urbanietz and Dunemann, 2005). Additionally, to reduce the burden on the growing plant material, many laboratories have conserved isolates of different powdery mildew fungi on detached leaves or leaf segments of cereals (Brown and Wolfe, 1990; Wyand and Brown, 2003), cucurbits (Shishkoff and Mcgrath, 2002; Romero et al., 2003), tomato (Kiss et al., 2001), and apple (Scheewe and Ketzel, 1994; Urbanietz and Dunemann, 2005). In a previous study, three main methods were applied to conserve grapevine powdery mildew: i) continuous propagation of grapevine powdery mildew on susceptible grapevine plants; ii) maintenance of the pathogen on detached leaves of susceptible grapevine plants via contact with infectious leaves; and iii) maintenance of the pathogen on detached leaves of susceptible grapevine plants by spraying the surface of detached leaves with a spore suspension.
The most economically important disease of cultivated grapevines worldwide is powdery mildew caused by the biotrophic fungal pathogen Erysiphe necator. To integrate effective genetic resistance into cultivated grapevines, numerous disease resistance screens of diverse Vitis germplasm, including wild species, have been conducted to identify powdery mildew resistance, but the results have been inconsistent. Here, a new powdery mildew isolate that is infectious on grapevines, designated Erysiphe necator NAFU1 (En. NAFU1), was identified and characterized by phylogeny inferred from the internal transcribed spacer (ITS) of pathogen ribosomal DNA sequences. Three classical methods were compared for the maintenance of En. NAFU1, and the most convenient method was maintenance on detached leaves and propagation by contact with infected leaves. Furthermore, controlled inoculations of En. NAFU1 were performed using detached leaves from 57 wild Chinese grapevine accessions to quickly evaluate powdery mildew resistance based on trypan blue staining of leaf sections. The results were compared with previous natural epidemics in the field. Among the screened accessions inoculated with En. NAFU1, 22.8% were resistant, 33.3% were moderately resistant, and 43.9% were susceptible. None of the accessions assessed herein were immune from infection. These results support previous findings documenting the presence of race-specific resistance to E. necator in wild Chinese grapevine. The resistance of wild Chinese grapevine to En. NAFU1 could be due to programmed cell death. The present results suggest that En. NAFU1 isolate could be used for future large-scale screens of resistance to powdery mildew in diverse Vitis germplasms and investigations of the interaction between grapevines and pathogens.
The Podosphaera fusca TUB2 gene, a molecular "Swiss Army knife" with multiple applications inpowdery mildew research
2014, Fungal Biology
Citation Excerpt :
Disease symptoms were estimated by percentage quantification of the leaf area covered with powdery mildew by an image analysis of pictures of powdery mildew-infected zucchini cotyledons. The image analysis software Visilog 4.1 (Noesis) was used according to Romero et al. (2003). The Podosphaera fusca TUB2 gene was also used as a molecular target in the quantification of fungal growth in host tissues by real-time PCR technology.
The powdery mildew fungus Podosphaera fusca (synonym Podosphaera xanthii) is the main causal agent of cucurbit powdery mildew and one of the most important limiting factors for cucurbit production worldwide. Despite the fungus' economic importance, very little is known about the physiological and molecular processes involved in P. fusca biology and pathogenesis. In this study, we isolated and characterised the β-tubulin-encoding gene of P. fusca (PfTUB2) to develop molecular tools with different applications in powdery mildew research. PfTUB2 is predicted to encode a protein of 447 amino acid residues. The coding region is interrupted by six introns that occur at approximately the same positions as the introns present in other fungal TUB2-like genes. Once cloned, the PfTUB2 sequence information was used in different applications. Our results showed that the TUB2 gene is a good marker for molecular phylogenetics in powdery mildew fungi but it is unsuitable for the analysis of intraspecific diversity in P. fusca. The expression of PfTUB2 was proven to be stable in different temperature conditions, supporting its use as a reference gene in quantitative gene expression studies. Furthermore, an allele-specific PCR assay for the detection of resistance to methyl-2-benzimidazole carbamate (MBC) fungicides in P. fusca was developed based on the correlation between the single amino acid change E198A in β-tubulin and the MBC resistance phenotype. Lastly, PfTUB2 was used as a target gene in the development of a high-throughput method to quantify fungal growth in plant tissues.
Invitro compatibility of microbial agents for simultaneous application to control strawberry powdery mildew (Podosphaera aphanis)
2013, Crop Protection
Citation Excerpt :
The hyperparasitic fungus Ampelomyces quisqualis Ces. has shown a high biocontrol potential against powdery mildew on different crops under controlled conditions (Elad et al., 1996, 1998; Kiss, 2003; Kiss et al., 2004; Pertot et al., 2008; Romero et al., 2003, 2004, 2007). Trichoderma harzianum Rifai T39 controlled powdery mildew on detached strawberry leaves and on greenhouse-grown cucumber (Elad et al., 1998; Pertot et al., 2008), while Penicillium oxalicum Currie & Thom significantly reduced the incidence of P. aphanis on strawberry runners of various cultivars and lines in both growth chambers and field trials (De Cal et al., 2008).
Biological control of plant pathogens on strawberries may be improved by the simultaneous application of different biological control agents (BCAs). Therefore, the compatibility of various BCAs which had previously shown to be effective against powdery mildew (Podosphaera aphanis (Wallr.) U. Braun & S. Takam) under laboratory conditions was examined in vitro. Inhibitory effects between fungal and bacterial BCAs were demonstrated in dual culture tests on two solid nutrient media. Leaf disc assays with single and multiple strain treatments demonstrated either unaffected or significantly improved control of P. aphanis for many multiple strain treatments, even if antagonistic interactions previously occurred in dual culture tests. Highest inhibition of powdery mildew conidiation (80.7% reduction) was achieved with multiple strain treatments with Bacillus subtilis FZB24 and Metarhizium anisopliae (p < 0.001). In this combination, conidiation was 3.7 times lower than in single treatments with B. subtilis indicating synergistic interactions between these BCAs. Combinations of Trichoderma harzianum T58 and B. subtilis FZB24 showed antagonistic interactions in dual culture tests as well as in leaf disc assays. In this combination, powdery mildew conidiation on leaf discs was four times higher compared to single treatments with T. harzianum T58.
Foliar application of microbial-enriched compost tea enhances growth, yield and quality of muskmelon (Cucumis melo L.) cultivated under fertigation system
2013, Scientia Horticulturae
Citation Excerpt :
It has been reported that biocontrol agents significantly affect the development of powdery mildew pathogen on melon leaves, including haustoria, conidiophores and conidia development (Romero et al., 2003). As a result, biological approaches may be an efficient strategy in the management of powdery mildew disease (Romero et al., 2003, 2007). Powdery mildew colonisation on melon leaf surfaces receiving foliar application of microbial-enriched CT as reported in the present study was suppressed apparently due to the inhibition of conidial germination The authors concluded that, antibiosis might be one of the responsible mechanisms of action underlying behind this observation as well as other factors (Naidu et al., 2012).
Microbial-enriched compost tea (CT) is a water extract of compost that is amended with nutrient supplements during brewing to enhance their microbial diversity. The potential use of fertigation nutrients via drip irrigation system followed by weekly foliar application of microbial-enriched CT on growth of muskmelon (Cucumis melo L.) and suppression of powdery mildew caused by Golovinomyces cichoracearum DC. was studied under rain shelter conditions. Full and half strength fertigation nutrients in combination with weekly foliar application of microbial-enriched CT, fungicide (Daconil^®@2 g L⁻¹) or water as a control were utilised in this study. The study showed that there was no added advantage in using full strength fertigation nutrients in terms of chlorophyll content, mean flower formation, mean fruit set, disease severity, and disease progress (AUDPC) or epidemic rate. A repeat trial was also conducted using half strength fertigation nutrients (twice a day) in combination with weekly foliar application of microbial-enriched CT or Daconil^®, as a result there was reductions in the disease severity by 38 and 21%, respectively. In addition, a delay in disease onset for two weeks was observed in the plants treated with either microbial-enriched CT or Daconil^®. The experimental results revealed significant variations in the yield and fruit qualities amongst the treatments. There were 18.3, 16.21, 8.81, 7.11 and 7.50% increases in mean fruit fresh weight (kg), total soluble solids concentration (°Brix), firmness (N), linear increment in the diameter (cm) and mesocarp size (cm) of muskmelon fruits, respectively after the application of half strength fertigation nutrients in combination with the weekly foliar application of microbial-enriched CT as compared with the control. Thus, it is rational to conclude that a reduced strength of the nutrients in the fertigation systems in combination with weekly foliar application of microbial-enriched CT could be used successfully as a biofertiliser and a bioprotectant on muskmelon crop without compromising their fruit quality.

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Effect of mycoparasitic fungi on the development of Sphaerotheca fusca in melon leaves

Crop Protection

Crop Protection

The Journal of Biological Chemistry

Biological Control

Mycological Research

Journal of Invertebrate Pathology

Biological Control

Disruption of chlorophyll organization and function in powdery mildew-diseased cucumber leaves and its control by the hyperparasite Ampelomyces quisqualis

Phytopathology

The potential of mycoparasites for biological control of plant diseases

Annual Review of Phytopathology

Cultivo in vitro de Sphaerotheca fuliginea (Schlecht. ex Fr.), efecto de diferentes fuentes de carbono sobre su desarrollo

Boletin de Sanidad Vegetal Plagas

Biological control in the phyllosphere

Annual Review of Phytopathology

Ultrastructural and cytochemical investigations of antagonistic effect of Verticillium lecanii on cucumber powdery mildew

Phytopathology

Powdery mildews. Recent advances toward integrated control

Epidemiology of powdery mildews

Epifluorescence microscopy of Sphaerotheca fuliginea race 2 on susceptible and resistant genotypes of Cucumis melo

Phytopathology

Comparison of three biological control agents against cucumber powdery mildew (Sphaerotheca fuliginea) in semi-commercial-scale glasshouse trials

European Journal of Plant Pathology

Management of powdery mildew and gray mold of cucumber by Trichoderma harzianum T39 and Ampelomyces quisqualis AQ10

Biocontrol

Partial control of grape powdery mildew by the mycoparasite Ampelomyces quisqualis

Plant Disease

Myths and dogmas of biocontrol. Changes in perceptions derived from research on Trichoderma harzianum T-22

Plant Disease

Effect of seventeen fungicolous fungi on sporulation of cucumber powdery mildew

Netherlands Journal of Plant Pathology