摘要:

AbstractThe number of crops of conidiophores and conidia ofPeronospora pisiproduced on a single lesion on leaflets of pea (Pisum sativumL.) was determined bothin vitroandin vivoby artificial inoculation. Only two crops were producedin vitrowhereas five crops were discerned underin vivoconditions. There was a marked difference in the size of conidiophores and conidia formed under the above two conditions.Temperature had a marked effect on the penetration of pea leaflets by conidial germ tubes ofP. pisi.The pathogen penetrated the leaf tissues at 12‐14°C in 8.0‐8.5 h whereas more time (9.5‐16.5 h) was required for penetration at higher temperatures (15‐18°C).Use of systemic fungicides has been suggested to control downy mildew of pea because of its capacity to produce more than one crop of propagules on the same lesion.Maximum spore discharge inP. pisiwas observed from 9.00 to 15.00 hours. However, presence of light, high temperature, lack of moisture on leaf surface and wind velocity affected spore

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb04456.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractTobacco callus cultures from aThielaviopsis basicola(Berk. et Br.) Ferraris resistant cultivar were less severely colonized than callus cultures from susceptible cultivars by the pathogen at all concentrations of kinetin and α‐indoleacetic acid tested. However, at concentrations where these substances influenced the morphology of the callus cultures they also influenced the degree of colonization by the fungus. Incorporation of T‐DNA ofAgrobacterium tumefaciensinduced susceptibility in tissue culture of the resistant cultivar but did not significantly modify the reaction of the susceptible cultivar te

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb04457.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractScopolin concentration increased in tissue cultures whereThielaviopsis basicolagrowth ceased (primary and established callus cultures of the resistant tobacco cultivar Ky 170) while it decreased in tissue cultures where fungal growth persisted (primary and established callus cultures of the susceptible tobacco cultivar Ky 151 and crown‐gall cultures of Ky 170 and Ky 151). The concentration of chlorogenic acid, scopoletin, and two other unknown soluble phenols varied after inoculation and no, correlation with tissue culture resistance could be established. Incorporation ofAgrobacterium tumefaciensT‐DNA in the genome of both cultivars induced a drastic reduction of scopolin in inoculated tissue cultures. T‐DNA incorporation had less, influence on uninoculated tissues. Scopolin at concentrations found in tissue cultures was not toxic to the f

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb04458.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAntigen preparation from plant tissues of pathogenic mycoplasms (MLO) causing flavescence doree diseaseExtraction and purification of plant yellow's pathogen mycoplasms (MLO) from plant tissues is a difficult problem. It concerns indeed non cultivable, heterogeneous and fragile organisms which are localized in the fibrous and resistant phloem tissue. In a work directed by an infectivity test by leafhopper injection, our laboratory investigated the best host plant and the best extraction method for this type of pathogen.Broad bean,Vicia fabagave better extracts thanVitis vinifera.Stems are better than petioles or lamina. The best results were obtained with the top region of the stem, at the level where symptoms are apparent on young plants.The most efficient mincing method is achieved with razorblades moved alternatively by the rapid vertical movement of an electric knife.The extraction medium already published (Caudwelland Kuszala1986) has to be modified for plants by various additional components, histidine buffer, antioxidizers (glutathion 0.2 mg per ml) and polymers 0.5 to 1 p 100 PVP or Polyclar, 1–2 p 100 PEG). 1 g of plant infected tissue is minced in 4 ml of medium. The extracts are filtered through a 100 mesh nylon cloth. After this stage the purification method goes parallel to that used for leafhopper extracts (Caudwelland Kuszala1986). It is possible to obtain 4 × 106infectious units from 1 g of broad bean stem (for calculation, see C 1986). It is possible to obtain 4 × 106infectious units from 1 g of broad bean stem (for calculation, see Caudwell1977).The possibility to extract MLO, either from infectious leafhoppers or from diseased plants enabled cross immunological assays involving antigens from one host and antibodies directed towards the other host antigens. The first step was the successful ISEM visualization of ttie MLOs (Caudwellet al. 1982), the second is the immunoenzymatic MLO‐detection (Boudonet al.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb04459.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractIn a study using scanning electron microscopy (SEM), the mode of hyperparasitism ofConiothyrium minitanson its hostSclerotinia sclerotiorumwas investigated. The SEM micrographs confirm previous reports, from light microscopic studies, that hyphal tips ofC. minitansinvade the host hypha by direct penetration, without developing appressoria, and that indentation of the host cell wall at the point of penetration is often evident. There is no functional distinction between amain branch and a side branch hypha of the hyperparasite and tips of either type of hyphae are capable of invading host hyphae by direct penetration.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb04460.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAvocado cultivars were defined as susceptible and resistant toColletotrichum gloeosporioidesdepending upon the length of the incubation period of the disease after fruit softening. In the susceptible cultivars Fuerte, Horshim, Vurtz, Rincon, and Benik, epicatechin concentration of the peel decreased to 60‐130 μg.g−1, fr. wt. at fruit softening and symptoms appeared on the same or one day later. In the resistant cultivars Hass, Nabal, Netaim and Pinkerton, epicatechin concentration was still 632–1740 μg.g−1fr. wt. when fruit softening and symptoms appeared only 4‐10 days later. When susceptible Fuerte fruits became soft the concentration of the antifungal compound 1‐acetoxy‐2‐hydroxy‐4‐oxo‐heneicosa‐12,15 diene, had decreased to 120 μg.g−1fr. wt. and symptoms appeared. In resistant Hass fruits, the antifungal diene was still 238 μg.g−1fr. wt. at fruit softening; and it had further decreased to 159 μg.g−1fr. wt. when symptoms appeared, four days later. A modified atmosphere and 0.2 M CaCl2infiltration both delayed softening of Fuerte fruits; but symptom appearance on these fruits was related to diene decrease and not to fruit softening.The results are discussed in relation to the hypothesis that the susceptibility of avocado cultivars to post‐harvest decay byC. gloeosporioidesis related to the degradation of the antifungal diene, catalyzed by avocado lipoxygenase, the activity of which is regulated by the

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb04461.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractCynara rhabdovirus (CyRV) was isolated from symptomless artichoke plants in southern Italy usingNicotiana langsdorffiias susceptible host and immune serum to artichoke latent virus to eliminate this virus from inoculum. CyRV can infect several solanaceous species, has thermal inactivation point of 40‐45°C, dilution end point between 10−2and 10−5and longevityin vitroat 4 and 20°C of 4‐5 days and 6‐24 h, respectively. It was purified and used for preparing antisera with homologous titre varying from 1: 16 to 1: 64. In decoration tests, the virus did not react against antisera to eggplant mottled dwarf virus (EMDV) and its antiserum did not decorate ivy vein clearing virus (IVCV). Ultrastructural aspects of CyRV infection inDatura stramoniumandNicotiana glutinosawere very like those described for the same virus in the past except for presence of longer virions which were often encountered in infected cells during

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb04462.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe amount of chloroplast 23s rRNA relative to either DNA or to cytoplasmic 28s rRNA was reduced in young wheat leaves infected with wheat streak mosaic virus.Chlorophyll was reduced in infected leaves. Fresh weight per leaf and DNA content per leaf were reduced in infected leaves, but DNA per g was increased.Cytoplasmic ribosomal RNA appeared to degrade more slowly during senescence in infected leaves than in uninfected. Virus was undetectable by density gradient centrifugation in systemically infected leaves less than 6 cm long and reached its highest concentration when young leaves reached their maximum size. Mosaic developed in leaves that became infected when 5 cm long or less. Since the entire leaf eventually developed mosaic, the events leading to mosaic occur after cell division, which is limited, to the basal cm of young leaves.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb04463.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractGermination of nutrient‐amended chlamydospores of the threeformae specialesofFusarium oxysporumtested were inhibited in a suppressive soil collected from central Taiwan. The suppressive soil released a volatile substance when moistened with alkaline solution. The inhibition spectrum of the volatile substance was different from that of the suppressive soil. The inhibitory effect of the suppressive soil was greatly reduced when it was heat‐treated for 30 min at 40°C or higher. The inhibitory effect of the heat‐treated suppressive soil was restored after infestation with 1% conducive or suppressive soil for 14 days. However, infestation of heat‐treated conducive soil even with 1% suppressive soil did not render it suppressive. Amendment of suppressive soil with rose bengal, streptomycin or Rubigan completely or partially reduced the inhibitory effect. Increasing the total population of indigenous microorganisms in conducive soil by amendment with rice germ or soybean meal to about the same level as that in suppressive soil did not render it suppressive. Results suggest that a combination of biotic and abiotic factors is responsible for the inhibitory effect of the suppress

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb04464.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractEnzymes ofBotrytis cinereawere detectedin vitrousing various carbon sources. Pectin‐pectate as a sole carbon source induced both polygalacturonase (PG) and pectin lyase (PL) activity, whereas carboxymethylcellulose served as an inducer for cellulase (Cx) activity. PG activity appeared earlier than Cxactivity when induced by their respective sources. Both PG and PL activities were detected earlier and their level was higher on cell walls of the normal tomato fruit, than of thenormutant, and in each case activity was higher on cell walls of the mature fruits than of the mature‐green ones. Whereas relatively high rates of PG and PL activity were recorded on autoclaved tomato homogenate (TH) of both the normal and thenorfruits, only trace levels of PG activity were recorded on unautoclaved media, except for those prepared from ripe normal fruits, and no PL activity was detected on either of the unsterilized media.Botrytis‐infection resulted in PG activity in the enzyme‐lessrinandnormutant fruits at both stages of maturity and in the normal and hybrid fruits at their mature‐green stage. In the ripe normal and hybrid fruits, infection increased the level of PG activity recorded prior to inoculation. An association was drawn between the low PG activity recorded in thenormutant and its hybrid at initial stages of invasion and their resistance to infection.Following infection an increase in the level of Cxactivity over that recorded in healthy fruits was found in all the tomato genotypes, whereas no PL was recorded in either healthy or infect

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb04465.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY