摘要:

AbstractVerticillium chlamydosporiumproduced in submers culture several antifungal and/or phytotoxic compounds which were detected in a bioassay by using the pathogen‐host systemPuccinia coronataand oat seedlings. The antifungal compounds were also tested againstP. reconditaon wheat andP. sorghion corn seedlings. The production of the active metabolic compounds highly depended on the nutrient solution (peptone‐Czapek [PC] and malt extract [ME]) and on the fermentation times. Cell‐free filtrates of PC‐cultures of the fungus were highly phytotoxic; the fungitoxic and phytotoxic compounds were heat‐labile and dialyzable. The ethyl acetate extracts of the PC‐culture filtrates contained only the antifungal active substances. The antifungal compounds in ME‐culture filtrates proved to be heat‐stable, could be dialyzed and extracted with ethyl acetate. Ethyl acetate extracts of PC‐ and ME‐culture filtrates at concentrations of 500 μg/ml reduced rust disease incidence by up to 80 % compared to the control treatment.Further studies with extracts of ME‐culture filtrates displayed a distinct protective but no systemic activity. The extract interfered with the development of several infection structures of the rust fungi, mostly with the growth of germ tubes as well as with the formation of the aappressoria and haustorial mother cells. Three rust‐active fractions were obtained by preparative layer chromatography on silica gel. One of these fractions exhibited phytotoxic activity. The most active antifungal fraction is identical with the macrolid antibiotic monorden which caused a desorientated spiral growth inP. coronat

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01296.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA 48 h or 96 h period of waterlogging induced a partial rotting of the root system of 18 month old potted kiwifruit cuttings. However, root regeneration compensated for the loss of damaged roots and the plants remained healthy. Inoculation withPhytophthora cryptogeaunder low soil moisture conditions caused a small amount of root rotting (11 %) and regeneration of the roots occurred. Root rot was significantly increased when inoculations were combined with extended periods of waterlogging. Root rot incidence was highest (89 %) in inoculated plants exposed to periods of 96 h waterlogging. Regeneration did not occur with any of these plants and consequently, the shoot systems were severely damaged.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01297.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractEightFusariumspp. were isolated from greenhouse‐grown jimsonweed (Datura stramoniumL.) in Mississippi in 1990. Four isolates ofFusarium moniliformewere obtained and when grown on autoclaved rice, produced 115 to 3,200 mg/kg fumonisin B1, (FB1). Other fumonisin‐related compounds, such as FB2, FB3and FB4were also produced at levels of 240, 210 and 160 mg/kg, respectively.F. semitectum(1 isolates) was negative for production of fumonisin and other phyto‐toxins.F. oxysporutn(1 isolate) produced only 3.5 g/kg moniliformin. This is the first report of production of fumonisins byF. moniliformeisolated from weeds such as jimso

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01298.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA detached cotyledon pathogenicity test was devised for the isolation of UV‐induced mutants of the hemibiotrophie ascomycete pathogen ofBrassicaspp.,Pyrenopeziza brassicaedefective in pathogenicity determinants. At least 95 % of cotyledons of suitable susceptible cultivars of oilseed rape (Brassica napusL. ssp. oleifera cvs Shogun or Bolko) showed symptoms of disease (white spore pustules [conidiomata] on the surface of the cotyledon) within three weeks of inoculation of cotyledons with 104conidia ofP. brassicae.The test allowed rapid screening of UV‐induced mutants with a low frequency of false negatives. From 1,700 survivors of UV mutagenesis tested, 20 non‐pathogenic mutants were obt

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01299.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractCell‐free translation of soybean mosaic virus (SMV), strain G2 or G7, RNAs in the presence of fractionated leaf extracts from the cultivars Davis or Williams‘82 revealed no differences that were associated with disease resistance of the cultivars to the virus strains. Extracts of leaf tissue from Davis (resistant to strain G2) and susceptible Williams‘82 were fractionated into three broad peaks. Apparent proteinase activity was detected in peak II of both soybean cultivars in the cell‐free translation of SMV‐G2 or ‐G7 RNAs. Inhibition of translation occurred in the presence of peak extracts from either of the soybean cultivars at levels of 500 μ/ml and/or 1000 μ/ml of protein. No inhibition of proteolytic processing was observed by extracts from ei

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01300.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe antagonist strainsGliocladium virensG2 andTrichoderma harzianumT3 originally isolated from Pythium suppressive peat, and two benomyl‐resistant strains ofT. harzianum, T12B and T95, were evaluated as biological control agents of damping‐off and root rot of cucumbers in sphagnum peat caused byPythium ultimum. All strains were equally effective when applied as 1 % peat‐bran preparations, whereas the effectiveness of disease control was reduced at higher concentrations of the antagonists. The two wild‐type strains were also found to be effective when applied as conidial suspensions, and in this case no reduction in disease control was seen at higher concentrations.G. virensG2 andT. harzianumT12B showed antibiotic activity againstP. ultimuminin vitrotests; however there were no signs of mycoparasitism ofP. ultimumby any of the antagonist

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01301.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractTrichothecium roseum(Tr) has been shown to be a highly effective hyperparasite on conidia ofPestalotiopsis funerea(Pf)in vivoandin vitro.The stages of this spore parasitism are:positive tropism of Tr towards Pf conidia, contact between Tr and Pf, formation of simple or lobed appressoria of Tr on the host conidial surface, penetration of the attacked host cells from the base of the appressoria, development of host‐internal, mostly branching parasitic hyphae by Tr, desintegration, lysis and death of the parasitized host cells, exit of Tr from the destroyed host cells and its intensive sporulation over Pf remnants.Pf did not show any defence reactions against the attack by Tr.In addition to the antagonistic activities of Tr against Pf reported previously, which are due to extracellular toxins released by Tr, direct hyperparasitism is a second mechanism of antagonism, which contributes to the successful competitive ability of Tr in this fungal interactio

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01302.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of a range of commercially available C16and C18fatty acids, on the release of cutinase byAscochyta pisi, was studied. When juniperic acid was used as sole carbon source, cutinase activity was released in the culture medium, and was markedly enhanced by post‐treatment ofA. pisicultures with acetone used as enzyme extractor. Without acetone, less cutinase was naturally released in culture medium containing juniperic acid at 0.5 %, than at 0.0l % or 0.05 %. Upon post‐treatment with acetone, the same level of cutinase was released with all three concentrations, thus suggesting that the enzyme was induced, but not completely released in the presence of 0.5 % juniperic acid. When ricinelaidic or ricinoleic acids were supplemented at 0.5 % to cutin in the culture medium, they strongly inhibited the release of cutinase, even with acetone post‐treatment. Comparable inhibition by ricinoleic acid was also observed when juniperic acid was used as cutinase inducer, thus suggesting that not only the release, but also the production of cutinase were inhi

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01303.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThree‐ and four‐fold increases in chitinase activity were detected in the youngest, fully expanded leaf (L1) ofStylosanthes guianensiscv. Endeavour following inoculation of the second youngest, fully expanded leaf (L2) with virulent Type B and Type A isolates ofColletotrichum gloeosporioidescompared with chitinase activity in L1leaves of uninoculated plants. Only small increases in β‐1,3‐glucanase were detected in L1leaves of systemically protected plants. Chitinase activity was maximal in leaf L136 to 48 h after inoculation of leaf L2, and this was coincident with the onset of resistance to anthracnose in L1leaves. Chitinase activity also increased in L1leaves inoculated with a weakly pathogenic isolate ofC. gloeosporioides. Resistance developed in these L1leaves to subsequent infection by a virulent isolate of the pathogen approximately 36 h after protective‐inoculation with the weakly pathogenic isolate.Two chitinase isozymes, with molecular weights of 65,000 daltons (pI 3.1) and 54,000 daltons (pI 4.0), were separated from extracts ofC. gloeosporioides‐challengedS. guianensiscv. Endeavour leaves.S. guianensischitinase caused death ofC. gloeosporioideshyphae, particularly in the presence of β‐1,3‐glucanase. Mycelial viability declined as activity of chitinase was increased in mixtures containing a fixed activity o

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01304.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractUsing transmission electron and fluorescent microscopes, Mycoplasma‐like organisms (MLOs) were found in phloem cells of stems and leaves ofAmmobium alatum. The diameter of these organisms ranged from 0.12–0.73 μm and averaged 0.4 μm. Symptoms induced by MLOs included chlorosis and reddening of leaves and winged stems, plant stunting and flower phyllody. This is the first report of MLOs associated with disease symptoms inA. a

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb01305.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY