Sclerotium Cepivorum Research Articles

English

One concern for garlic (Allium sativum Linnaeus) producers is the damage caused by the pathogen Sclerotium cepivorum Berk. Unfortunately, the genetic and molecular mechanisms that participate during S. cepivorum Berk pathogenesis are currently unknown. In order to identify and isolate genes that are differentially expressed by the fungus during garlic white rot pathogenesis, PCR-based suppression subtractive hybridization (SSH) was used. Combining SSH and cDNA arrays hybridization techniques, 120 ESTs whose expression is restricted to the pathogenic stage were identified and isolated. Fourteen ESTs showing higher expression in cDNA arrays were sequenced, these included homologues to oxaloacetate acetylhydrolase (Oah), cysteine desulfurase (Nfs 1p), regulator of drug sensitivity (Rds 1p), outer membrane protein (Omp 1) and cell wall adhesion (Fig2p). One selected EST with high homology to Oah gene, a putative virulence factor, was analyzed by RT-PCR. The possible role of Oah gene in the pathogenesis of this fungus toward garlic is discussed. The combined applications of SSH and cDNA arrays permitted global analysis of gene expression patterns in S. cepivorum Berk, as an initial stage to improve the knowledge at molecular level from fungal pathogenesis.   Key words: Pathogenesis, differential gene expression, suppression subtractive hybridization, cDNA arrays, Oah gene.

Variability in control of onion white rot by Trichoderma atroviride under different disease pressures

Pellet and solid substrate formulations combined with a soil drench formulation of Trichoderma atroviride were evaluated under varying disease pressures in field trials to determine which formulation(s) provided the best control of the soil-borne disease onion white rot. Under low (11.8%) (average Area Under the Disease Progress Curve (AUDPC): 5.94%), moderate (37.7%) (average AUDPC: 11.26%) and high (64.4%) (average AUDPC: 24.76%) disease pressure, the standard fungicide programme (procymidone coated seed plus tebuconazole foliar spray) gave statistically significant disease control (76.3%, 91.3% and 58.8%, respectively) compared with the untreated control. Under low and high disease pressure, significant control, equal to the fungicide treatment, was achieved with the T. atroviride pellet plus soil drench treatment (72.0 and 39.6%, respectively). However, no Trichoderma formulation gave significant control of onion white rot under moderate disease pressure (20.7–34.2% control). When disease progress was examined over time for each trial, it was evident that the onset of disease occurred later in the growing season at the moderate disease pressure site (3 months after sowing) compared with Trial 3 at the high disease pressure site (2 months after sowing). At the low disease pressure site, the low level of inoculum and disease incidence enabled T. atroviride to bring about disease control. These results indicated that the performance of T. atroviride may be influenced as much by the timing of disease onset as the absolute disease pressure.

Evaluation of Arbuscular Mycorrhizal Fungi and Trichoderma Species for the Control of Onion White Rot (Sclerotium cepivorum Berk)

The present study was carried out to evaluate the indigenous Arbuscular Mycorrhizal Fungi (AMF) and Trichoderma species isolated from rhizosphere soils of onion cultivated fields at Ambo and Toke Kutaye districts of West Showa, Ethiopia, and their effect on plant growth, and their biocontrol against onion white rot caused by Sclerotium cepivorum Berk. Five species with twenty isolates of Trichoderma were isolated and screened in vitro for the inhibition of S. cepivorum. Out of these, four isolates of Trichoderma spp viz. T. harzianum (ATh1), T. viride (ATv1), T. hamatum (NThm3), and T. koningii (QTk2), were found potent antagonists with mean percent inhibition of the pathogen, 65.4, 64.8, 54.3 and 53.5, respectively. Altogether, 10 AMF species representing four genera viz. Acaulospora, Gigaspora, Glomus, and Scutellospora, were isolated and identified. Six dominant species of AMF were selected and mass multiplied by using Sorghum vulgare Pers. as the compatible host plant. Among six AMF species, the potential efficient strain, Glomus aggregatum (Awaro isolate), was selected for using as bio control agent. The bio-control potential of these bio-agents against white rot pathogen was carried out under pot culture condition, using G. aggregatum alone or in combination with four isolates of Trichoderma spp. Incidence of S. cepivorum was significantly reduced in bulbs of onion (66.19%), and also improved plant growth was observed in plants inoculated with combined inoculation of G. aggregatun and T. harzianum (ATh1 isolate), followed by the combined inoculation of G. aggregatum and T. viride (ATv1) with pathogen (59.75%). Plants inoculated with S. cepivorum alone showed pronounced disease symptoms with mean disease incidence of 90.5%. The overall reduction in the incidence of white rot was 56.22% in the treatment of T. harzianum ATh1 isolate with pathogen, followed by 53.72% for G. aggregatum with pathogen. These results clearly pointed out that G. aggregatum and T. harzianum ATh1 isolate can block the severity of disease caused by S. cepivorum in onion. Use of these bio-control agents could be promoted as an active component of bio-intensive Integrated Disease Management Program (IDMP), under organic mode.

Compatibility of a Trichoderma atroviride biocontrol agent with management practices of Allium crops

Trichoderma atroviride Karsten strain C52 populations were measured in agronomic soils in combination with soil organic amendments, a nitrogen fertiliser, fungicides and diallyl disulphide (DADS) (a Sclerotium cepivorum sclerotial germination stimulant). Trichoderma atroviride C52 populations did not proliferate 2 weeks after inoculation in sandy soils (4.7 × 10 2 cfu/g soil) compared with silt loam soils (1.1 × 10 6–5.7 × 10 7 cfu/g soil), however, the addition of two blended pellet products containing poultry manure and other organic nutrients or humic acid plus organic matter to the sandy soil enabled populations to proliferate well (1.1–1.3 × 10 5 cfu/g soil). In vitro, twice field rate applications of urea reduced in vitro Trichoderma atroviride C52 growth (spore germination, germ tube length and mycelial growth), however, T. atroviride C52 populations were less sensitive to field rate applications of urea in field soil. Overall, T. atroviride C52 populations were not adversely affected when exposed to any of the fungicide soil treatments tested (populations ranged from 1.7 × 10 5–1.1 × 10 8 cfu/g soil). Volatiles of DADS reduced T. atroviride C52 mycelial growth in vitro when DADS was applied to the medium at standard and twice recommended field rates but not at half field rate. No spore germination occurred under any of the DADS in vitro treatments compared with 100% spore germination in the control. However, when DADS was applied to soil 4, 6 and 8 weeks before application of T. atroviride C52, populations were unaffected. Based on these data, an application strategy for the use of a commercial formulation of T. atroviride C52 in an integrated white rot management programme for onions is proposed.

Antifungal saponins from bulbs of white onion, Allium cepa L.

Three saponins, named ceposide A, ceposide B, and ceposide C were isolated from the bulbs of white onion, Allium cepa L. Elucidation of their structure was carried out by comprehensive spectroscopic analyses, including 2D NMR spectroscopy and mass spectrometry, and chemical evidences. The structures of the compounds were identified as (25R)-furost-5(6)-en-1β,3β,22α,26-tetraol 1-O-β-d-xylopyranosyl 26-O-α-d-rhamnoyranosyl-(1→2)-O-β-d-galactopyranoside (ceposide A), (25R)-furost-5(6)-en-1β,3β,22α,26-tetraol 1-O-β-d-xylopyranosyl 26-O-α-d-rhamnoyranosyl-(1→2)-O-β-d-glucopyranoside (ceposide B), and (25R)-furost-5(6)-en-1β,3β,22α,26-tetraol 1-O-β-d-galactopyranosyl 26-O-α-d-rhamnoyranosyl-(1→2)-O-β-d-galactopyranoside (ceposide C). The isolated compounds, alone and in combinations, were evaluated for their antimicrobial activity on ten fungal species. Antifungal activity of all three saponins increased with their concentration and varied with the following rank: ceposide B>ceposide A–ceposide C. We found a significant synergism in the antifungal activity of the three ceposides against Botrytis cinerea and Trichoderma atroviride, because growth of these fungi was strongly inhibited when the three saponins were applied in combination. In contrast, Fusarium oxysporum f. sp. lycopersici, Sclerotium cepivorum and Rhizoctonia solani were very little affected by saponins.

In vitro selection of resistant mutant garlic lines by using crude pathogen culture filtrate of Sclerotium cepivorum

In vitro treatment of tissue cultures of two garlic cultivars with crude culture filtrates from Sclerotium cepivorium was used to select somaclonal variants with enhanced resistance to white rot disease. The crude culture filtrate had a negative effect on callus induction and growth. It also inhibited the differentiation of adventitious buds. The inhibitory effects were greater at higher culture filtrate concentration. With increase in concentration of crude pathogen culture filtrate, rate of callus induction, callus survival, relative growth rate of callus, callus differentiation and number of divided shoots per callus decreased. The inhibitory effect for all the parameters was more visible when crude pathogen culture filtrate was used at 50% concentration or more. However, the performance of disease resistant cultivar Hangzhong Red Skin was better than Gailiang (disease susceptible cultivar) at higher concentrations of crude pathogen culture filtrate. Some somaclonal lines and plantlets (predominantly from Hangzhong Red Skin) that showed resistance to Sclerotium cepivorum were obtained at 50%concentration level of crude pathogen culture filtrate.

<i>In Vitro</i> Antagonist Action of <i>Trichoderma</i> Strains Against <i>Sclerotinia sclerotiorum</i> and <i>Sclerotium cepivorum</i>

Problem statement: Sclerotinia sclerotiorum and Sclerotium cepivorum are soil pathogens which have generated resistance to synthetic fungicides. One biological alternative to this problem is to select novel strains of Trichoderma with different mechanisms of action against these plant pathogens to ensure efficient control. Approach: In the present research was determined the antagonism effect of Mexicans Trichoderma strains on S. sclerotiorum and S. cepivorum in vitro. It was used dual culture technique by determining the percentage of mycelia growth inhibition, days to contact and antagonism levels proposed by Bell. It was also determined the effect of volatile compounds and metabolites compound from Trichoderma produced in solutions. Results: The mycelia growth inhibition of S. sclerotiorum and S. cepivorum were 45-63.8 and 50.9-81.5% respectively by the effect of Trichoderma strains. The T. ghanense and T. longibrachiatum (T15 and T10) inhibited in higher proportion to S. sclerotiorum. On the other hand T. inhamatum and T. asperellum (T32 and T11) inhibited in higher proportion to S. cepivorum. The days to contact between the Trichoderma and phytopathogen species were between two to three days. The levels of antagonism according to the Bell’s scale were different between the two species of phytopathogen and for Trichoderma strains were grouped into I and II class. The maximum inhibition effect by volatiles compound was occasioned by T. longibrachiatum with 31.5 (T3) and 59.2% (T10) on S. sclerotiorum and S. cepivorum respectively. Respect to metabolites, these shown high effects on phytopathogen growth, where T. asperellum is the more outstanding specie which produce totals mycelia growth inhibition of two phytopathogen species. Conclusion: T. longibrachiatum (T3 and T10) and T. asperellum (T1 and T11) were the most efficient species with the highest antagonist effects against S. sclerotiorum and S. cepivorum.

Differentiation of the causal pathogen of onion white rot Sclerotium cepivorum isolates by using the APIZYM system

The APIZYM system of detection of enzymes was proven to be useful in the differentiation of 15 European and Egyptian isolates of S. cepivorum, the incitant of onion white rot. The tested isolates produced alkaline phosphatase, esterase (c4), esterase lipase (c8), leucine arylamidase, valinearylamidase, trypsine, α-chymatrypsin, acid phosphatase, naphthol-AS-B1-phosphohydrolase, ß-galactosidase, ß-glucutronidase, α-glucosidase, ß-glucosidase and N-acetyl-ß-glucosaminidase and did not produced lipase (c14), crystine arylamidase, trypsine, ß-glucutronidase, α-mannosidase and α-fucosidase. According to enzyme activity, isolates can be divided into four groups (G). The differences between groups were in the activity of the enzymes α-chymotrypsin and α-glucosidase. The tested European isolates and the Egyptian isolates No.6 of the pathogen were in G1 and G2; however the rest of the Egyptian isolates were in G3 and G4.

Genetic enhancement of Trichoderma viride to overproduce different hydrolytic enzymes and their biocontrol potentiality against root rot and white mold diseases in bean plants

Genetic enhancement of Trichoderma viride to overproduce different hydrolytic enzymes and their biocontrol potentiality against root rot and white mold diseases in bean plants

Protein patterns in Relation to Virulence of Sclero-tium Cepivorum Berk. The Incitant of White Rot of Garlic

Protein patterns in Relation to Virulence of Sclero-tium Cepivorum Berk. The Incitant of White Rot of Garlic

Recombinant amaranth cystatin (AhCPI) inhibits the growth of phytopathogenic fungi

Phytocystatins are cysteine proteinase inhibitors from plants implicated in defense mechanisms against insects and plant pathogens. We have previously characterized an amaranth cystatin cDNA and analyzed its response to different kinds of abiotic stress [37]. In order to characterize amaranth cystatin, the coding sequence was expressed in Escherichia coli using the pQE-2 vector. Recombinant cystatin was predominantly found in the soluble fraction of the cell extract. Large amounts (266 mgL(-1)) of pure recombinant protein were obtained by affinity chromatography in a single step of purification. The amaranth cystatin with a pI 6.8 and an apparent 28 kDa molecular mass inhibited papain (E.C.3.4.22.2) (Ki 115 nM), ficin (E.C.3.4.22.3) (Ki 325 nM) and cathepsin L (E.C.3.4.22.15) (Ki 12.7 nM) but not stem bromelain (E.C.3.4.22.32), and cathepsin B (E.C.3.4.22.1) activities, in colorimetric assays. Furthermore, it was able to arrest the fungal growth of Fusarium oxysporum, Sclerotium cepivorum and Rhyzoctonia solani. It was further demonstrated that recombinant AhCPI is a weak inhibitor of the endogenous cysteine proteinase activities in the fungal mycelium. These findings contribute to a better understanding of the amaranth cystatin activity and encourage further studies of this protein.

The Effect of Nano-Silver Liquid against the White Rot of the Green Onion Caused by Sclerotium cepivorum

White rot, which is caused by Sclerotium cepivorum, is a lethal disease affecting green onions. Three different types of nanosilver liquid (WA-CV-WA13B, WA-AT-WB13 R, and WA-PR-WB13 R) were tested in several different concentrations on three types of media to assess their antifungal activities. Results from in vitro experiments showed that all three of the nano-silver liquids had more than 90% inhibition rates at a concentration of 7 ppm. Greenhouse experiments revealed that all of the nano-silver liquids increased biomass and dry weights, and there were minimal changes in the population of various bacteria and fungi from the soil of greenhouse-cultivated green onions. In addition, a soil chemical analysis showed that there were minimal changes in soil composition.

Phylogenetic placement of plant pathogenic Sclerotium species among teleomorph genera

Phylogenetic analyses and morphological characteristics were used to assess the taxonomic placement of eight plant-pathogenic Sclerotium species. Members of this genus produce only sclerotia and no fruiting bodies or spores, so Sclerotium species have been difficult to place taxonomically. Sequences of rDNA large subunit (LSU) and internal transcribed spacer (ITS) regions were determined for isolates of Sclerotium cepivorum, S. coffeicola, S. denigrans, S. hydrophilum, Ceratorhiza oryzae-sativae, S. perniciosum, S. rhizodes, S. rolfsii and S. rolfsii var. delphinii. Parsimony analysis grouped two species previously thought to be in the Basidiomycota, S. denigrans and S. perniciosum, within the Ascomycota; these species were found to have affinities with the teleomorph genera Sclerotinia and Stromatinia and the asexual Sclerotium cepivorum, which was known earlier to be related to Sclerotinia species. The other Sclerotium species were placed in one of two basidiomycetous groups, genera Athelia or Ceratobasidium. Based on rDNA analysis and morphology the basidiomycetous Sclerotium hydrophilum and S. rhizodes were transferred to genus Ceratorhiza, the anamorph of Ceratobasidium species. Sclerotium coffeicola was found to be close to S. rolfsii var. delphinii and S. rolfsii var. rolfsii, which was shown earlier to have an Athelia teleomorph.

Application of thymol and iprodione to control garlic white rot (Sclerotium cepivorum) and its effect on soil microbial communities

The effect of different dosages of thymol alone, iprodione alone and combinations of thymol and iprodione on white rot disease of garlic and its impact on soil microbial community structure were investigated under greenhouse conditions. Thymol alone or in combination with the fungicide iprodione did not appear to reduce either white rot incidence or soil sclerotia density as compared to an infected control. However, iprodione alone or in combination with thymol reduced soil fungal biomass. In addition, iprodione alone decreased soil microbial activity as estimated by fluorescein diacetate (FDA). Soil bacterial community structure as estimated by phospholipid fatty acid (PLFA) profiles was also was affected by both thymol and iprodione applications. The correlation biplot of the individual PLFAs and biocide treatment indicated that the treatments with thymol alone increased cyclopropyl fatty acid (cy17:0 and cy19:0), while the treatments with iprodione alone increased some saturated and branched fatty acids (principally i16:0, a15:0 and 18:0). In addition, taking into account PLFA biomarkers, thymol applications reduced Gram-negative bacteria in soil. To our knowledge, this research is the first report about the effect of a monoterpene (thymol) on soil microflora.

Molecular characterization of European and Egyptian isolates of Sclerotium cepivorum, the incitant of onion white rot

The tested European and Egyptian isolates of Sclerotium cepivorum were able to infect Giza 6 onion cultivar causing white rot disease with a different degrees of disease severity (ranging from sever to weak). The pattern of esterase isozymes produced by the tested isolates of the pathogen showed two main bands (arrows) which were different in density. Such differences in density of bands were present in every run and therefore appear to be indicators for differences among the tested isolates. Analysis of the protein pattern of the tested isolates of the pathogen indicated that the tested isolates had major proteins of a molecular weight of 52, 36, 23 and 16 kDa. Variation between isolates was detected by presence of bands of low molecular weight. Isolate Nos. 1, 4, 5, 7, 8, 9, 10 and 13 had a band at 17 kDa, whereas isolate Nos. 2, 3, 6, 11, 12, 14, and 15 had a band at 20 kDa. Using RAPD analysis to evaluate the genetic diversity of the tested isolates indicated that the tested field population of the pathogen was genetically heterogeneous but shared a number of common bands with molecular weights ranging from 650 to 2500 bp. Based on the DNA banding pattern the tested isolates can be assigned to seven genetically different groups. All tested isolates produced a band at 2500 bp except isolate No. 7. No correlation was exibited between patterns esterase isozmes, protein and DNA patterns of S. cepivorum isolates and their virulence or geographical origin.

MANAGEMENT OF Allium WHITE ROT CAUSED BY Sclerotium cepivorum BY USING COMPOST OF CERTAIN PLANT WASTES

A laboratory trial was conducted at 20 oC to investigate the effect of pH range on the growth and sclerotial formation of Sclerotium cepivorum, which causes white rot of Allium species. The obtained results indicated that pH 6 followed by pH 7 were the optimal pH degrees for growing the pathogen on PDA medium with production a large number of sclerotial populations. The lowest radial growth of S. cepivorum was observed at pH 8 and pH 4. No significant differences between diameters of each sclerotia was recorded within the tested pH range. 100 Sclerotia were exposed in the soil to one of three concentrations (5, 10 and 15 %) of composted onion, garlic and cabbage wastes under greenhouse conditions. Germination of the exposed sclerotia was determined on PDA medium in comparison with those unexposed. Failure of germination of the exposed sclerotia on PDA medium indicates damaged them within the soil in absence of the host. Due to use 15 % concentration of each compost type, higher efficiency at the first 15 exposed days was obtained. After 30 exposed days, suppressive effects of all applied concentrations of each compost type against viability of the treated sclerotia were paralleled increased in comparison with almost effect showed in control. Destroyed percentages of the exposed sclerotia were approximately pointed after 45 exposed days to the investigated waste types. Whenever, maximal mean values of the destroyed sclerotia were done and reached 75.70, 74.26 and 72.26 % due to use of the composted garlic, onion and cabbage wastes, respectively, in comparison with 8.30 % for control in absence of the host. Accordingly, great amounts of NH4, NO3, P, K and SO4 were accumulated within the treated soils in comparison with the free soils from treatments. However, potential use of the composted wastes could be attributed to trick and destruction of the vast majority of sclerotia in the field, consequently reduces the risk of the pathogen spread to neighboring fields.

COMPARATIVE STUDY BETWEEN CHEMICAL AND NON-CHEMICAL CONTROL AGAINST Sclerotium cepivorum, THE CASUAL WHITE ROT OF ONION UNDER EGYPTIAN CONDITIONS.

Sclerotium cepivorum one of the most destructive soilborne pathogens affecting onion and other Allium species and causing considerable damage to the host under congenial environments. In this work, it was isolated from North Egypt; many attempts were done to control onion white rot disease caused by the pathogen. Three fungicides; procimidone (sumisclex®25), vinclozolin (Ronilan) and tolclofos-methyl (Rizolex) were used against S. cepivorum and compared with a some biological non-chemical treatments. These treatments include a five antagonistic fungi, two antagonistic bacteria, three essential oils and three plant extracts. Among all fungicides tested, it was found that procymidone application was the best chemical treatment giving 100% inhibition in mycelial growth and reduction of sclerotia germination at all concentrates tested, in-vitro. While, T. harzianum was the best antagonistic fungi against the pathogen giving 82.8% reduction. On the other hand, Pseudomonas fluorescensand Bacillus subtilis have achieved complete inhibition of mycelial growth giving 100 and 94.00%, respectively and suppressed completely sclerotial germination when exposed to bacterial culture in half-strength Nutrient Broth (NB). Among all tested essential oils, it was noticed that, cinnamon (Cinnamomum zeylanicum) was the best essential oil for reducing mycelial growth giving 100% at 0.50 and 0.75%.While the cinnamon extract was the best against S. cepivorum with 94.40% inhibition in mycelial growth at 50% concentrate and completely suppressed sclerotial germination. Conversely, onion white peels extract gave the lowest rate of mycelium growth reduction giving (11.11%) and stimulated sclerotial germination than other extracts.

Western Ontario Regional Meeting, 2008

Biological control products reduce the inoculum of Sclerotium cepivorum, the causal agent of onion white rot. S. Balint, G.J. Boalnd, and M.R. McDonald. Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; and (G.J.B.) Department of Environmental Biology, Bovey Building, University of Guelph, Guelph, ON N1G 2W1, Canada Verticillium resistance in tomato is a concerted effort of early and late defense response genes. C.D.M. Castroverde, H.O. Shittu, R.N. Nazar, and E.J. Robb. Department of Molecular and Cellular Biology, College of Biological Science Axelrod Building 201, University of Guelph, Guelph, ON N1G 2W1, Canada The molecular identification and characterization of host proteins associated with soybean mosaic virus infection X. Cui and A. Wang. Southern Crop Protection and Food Research Centre, Agriculture and Agri0Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada Multi-site mutations in β-tubulin gene sequences are involved in thaibendazole resistance in Penicillium spp. collected from Southern Ontario. M. Czerwinski, V. popovic, and D. Errampalli. Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, Vineland Station, 4902 Victoria Avenue North, ON L0R 2E0, Canada Effect of seeding date and fungicide on incidence and severity of clubroot of Asian vegetables. K.C. Kalpana, M.R. McDonald, B.D. Gossen, and S.M Westerveld. Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; (B.D.G.) Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2, Canada; and (S.M.W.) Simcoe Research Station, Department of Plant Agriculture, University of Guelph, 1283 Blueline Road, P.O. Box 587, Simcoe,On N3Y 4N5, Canada A novel technology to extract nucleic acids from defferent environmental samples including plant, water, and soil W.-S. KIm and Y. Haj-Ahmad. (W.-S.K., Y.H.-A.) Norgen Biotek Corp., 3430 Schmon Parkway, Thorold, ON L2V 4Y6, Canada; and (Y.H.-A.) Brock University, 500 Glenridge Avenue, St.Catherines, ON L2S 3A1, Canada Reactive oxygen species scavengers and light influence the formation of stroma and apothecia by virulent, asymptomatic, and hypovirulent isolates of Sclerotinia homoeocarpa A.M. Orshinsky and G.J. Boland. Department of Environmental Biology, Bovey Building, University of Guelph, Guelph, ON N1G 2W1, Canada Detecting ascospores of Sclerotinia sclerotiorum in carrot crops in Ontorio — prelude to regional level forecasting of sclerotinia rot of carrot M. Parker, M.R. McDonald, and G.J. Boland. Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; and (G.J.B.) Departmeny of Environmental Biology, Bovey Building, University of Guelph, Guelph, ON N1G 2W1, Canada Differential gene expression in tomatoes during dual infections with an endophytic and a pathogenic Verticillium H.O. Shittu, C.D.M. Castroverde, R.N. Nazar and J. Robb. Departmeny of Molecular and Cellular Biology, College of Biological Science, Axelrod Building 201, University of Guelph, Guelph, ON N1G 2W1, Canada Deoxynivalenol (DON), 15-ADON, and 3-ADON level in wheat in Ontario. L. Tamburic- Ilincic, D. Gaba, T. Nowicki, and A. Schaafsma. Ridgetown Campus, University of Guelph, 120Main Street East, Ridgetown, ON N0P 2C0, Canada; and (D.G., T.N.) Grain Research Laboratory, Canadian Grain Commission, 1404-303 Main Street, Winnipeg, MB R3C 3G8, Canada

Effects of Glomus intraradices and onion cultivar on Allium white rot development in organic soils in Ontario

Commercial products containing formulations of the vesicular-arbuscular mycorrhiza (AM) Glomus intraradices were assessed for their effectiveness in suppressing Allium white rot (WR) on onions (Allium cepa) in organic soils and compared with the fungicide Folicur 3.6F (430 g a.i./L tebuconazole) under field conditions. The trials were conducted during 2000 and 2001 in commercial onion fields in the Holland-Bradford Marsh in Ontario. The AM product MIKRO-VAM, which is used in transplanted onions, reduced the incidence of WR by almost 50% compared with the untreated control and was comparable with that of the fungicide treatment, Folicur 3.6F, applied according to label recommendations. This is one of the few studies to demonstrate season-long disease suppression with AM under field conditions, and it is the first to show that the AM products can be as effective as a fungicide treatment under commercial production practices. A consistent difference in incidence of WR was found between the cultivars 'Hoopla'...

Composition of the Essential Oil of Spontaneous Rosmarinus officinalis from Greece and Antifungal Activity Against Phytopathogenic Fungi

The chemical composition of the essential oil of spontaneous Rosmarinus officinalis from Greece was analyzed by GC and GC/MS and tested for its antifungal activity against five phytopathogenic fungi (Sclerotinia sclerotiorum, Phytophthora nicotianae, Sclerotium cepivorum, Fusarium oxysporum f. sp. dianthi and Fusarium proliferatum). Thirty-seven components compounds representing 97.3% of the total oil were identified. The major constituents were α-pinene (24.1%), camphor (14.9%), 1,8-cineole (9.3%), camphene (8.9%), α-terpineol (8.8%) and borneol (8.0%). The most sensitive fungus was Ph. nicotianae, followed by S. sclerotiorum, S. cepivorum, F. proliferatum and F. oxysporum f. sp. dianthi.