摘要:

SummaryTwo wild‐type strains and three benomyl‐resistant mutants of the antagonistic ascomyceteTalaromyces flavuswere crossed in six combinations, two of which yielded hybrid cleistothecia. Parental strains and their ascospore progenies varied in several traits considered to play an important role in the capacity to control soilborne fungal pathogens: extracellular activities of glucose oxidase and cell‐wall degrading enzymes, antibiosis towardsVerticillium dahliae, and parasitism and biocontrol ofSclerotium rolfsii.A non‐Mendelian quantitative mode of inheritance was found for β‐1, 3‐glucanase and chitinase activities but only the latter exhibited a normal frequency distribution. Some of the progenies exhibited higher glucanase and chitinase activities than those found in the parental strains. Progeny analysis for chitinase, glucanase, cellulase, and glucose oxidase activities revealed no genetic association between any two of these enzymes. Antibiosis was correlated with glucose‐oxidase activity in one cross, but not in the other. The ability to reduce bean root rot caused byS. rolfsiiwas correlated with mycoparasitic activity againstS. rolfsiisclerotia in one cross, but not in the other. One out of the 20 progenies tested was able to reduce bean root rot more effectively than its parent strains, thus demonstrating the feasibility of improving a biocontrol agent by convent

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03466.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummarySystemic interactions of long duration among the Group I] Citrus Viroids, CVd‐IIa and CVd‐IIb were investigated by grafting buds from established citron (Citrus medicaL.) sources containing single viroids to a common healthy seedling. In healthy tissues, the two viroids became established in approximately equal titres as a mixed infection. By contrast, tissues that grew from the CVd‐IIa or CVd‐IIb source buds contained only trace amounts of the heterologous invading viroids.This interference between CVd‐IIa, a mild exocortis agent, and CVd‐IIb, the cachexia agent, was also demonstrated in the presence of CEVd, the severe exocortis agent but not a Group II viroid. When a CVd‐IIb bud was propagated on a citron containing CVd‐IIa, a dramatic reduction in the titre of CVd‐IIb was observed.The interference between CVd‐IIa and CVd‐IIb indicates that the mild and relatively innocuous isolate, CVd‐IIa, can interfere with the replication and/or accumulation of the severe cachexia agent, CVd‐IIb, in citrus. This offers a potential practical approach for the control of cachexia in commercial plantings

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03467.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe distribution and spread of hop latent viroid (HLVd) in two adjacent plantings of the hop cultivars Omega and Wye Challenger have been studied for three seasons. The planting of cv. Omega was heavily infected at the start of the survey and spread was rapid; the density of infection was lower in the planting of cv. Wye Challenger and spread was much slower. It is not known whether the difference in rate of spread was a varietal effect or because of the higher density of infection in the Omega planting. The distribution of known infections in 1991 suggests that plant‐to‐adjacent‐plant spread, either by contact or on tools, does occur. However, the overall distribution of infection and the occurrence of new infections not adjacent to existing ones, suggests that this is not the only means of transmission; whether a vector is involved is not

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03468.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryA polymerase chain reaction (PCR) protocol, previously designed for amplification of a DNA fragment from aster yellows mycoplasmalike organism (MLO), was employed to investigate the detection of MLO DNA in field‐collected andin vitromicropropagated plants. PCR with template DNA extracted from symptomatic, naturally‐infected samples ofBrassica, ChrysanthemumandHydrangea, each yielded a DNA band corresponding to 1.0 Kbp. However, no DNA product was observed when either infectedRanunculus(with phyllody disease) orGladioluswith (symptoms of ‘germs fins’) was used as source of template nucleic acid for PCR; further experiments indicated absence of target DNA in the case ofRanunculusand the presence of substances inGladioluswhich inhibited the PCR. The MLO‐specific DNA was detected by PCR using less than 95 pg of total nucleic acid (equivalent to total nucleic acid from 1.9, ug tissue) in the case of field‐collectedHydrangeaand less than 11.4 pg of nucleic acid (equivalent to total nucleic acid from 19 ng of tissue) in the case of field‐collectedBrassica.The findings illustrate highly sensitive detection of MLOs in both field‐grown andin vitromicropropagated

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03469.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryCoconut foliar decay virus (CFDV) occurs at a very low concentration in coconut palm. A 1203 nucleotide segment of the sequenced encapsidated circular single‐stranded 1291 nucleotide CFDV‐DNA has been amplified and transcribed for use as a32P cDNA probe for the virus. A rapid method for the extraction of DNA from coconut palm has been devised for a dot‐blot hybridisation assay using this probe. An alternative non‐radioactive probe has also been developed for future use in CFDV diagnosis.CFDV‐DNA was shown to be distributed unevenly in a range of infected palms, necessitating the use of multiple sampling to reliably detect infection in diagnostic tests. Viral DNA was detected in symptomatic and asymptomatic palms of both high and low susceptibility, in disease‐free tolerant cultivars, and in palms in remission from disease. Within the same palm, detectability of viral DNA varied little within leaflets, but varied more within and between fronds. CFDV‐DNA was detected 6–8 months after insect‐mediated inoculation, and symptoms generally appeared after another 1–4 months.In situhybridisation of rachis tissue showed localisation of DNA within the phloem, but its distribution in the phloem was uneven. CFDV‐DNA was detected in tissue adjacent to and within necrotic zones which develop into the petiolar lesions associated with the disease‐specific collapse of fronds.Virus was detected in the body of the insect vector, and, where its distribution could be resolved, in the abdom

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03470.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryVirus transmission bait tests with single trichodorid nematodes from England, the Netherlands, Scotland or Sweden showed that a substantial degree of specificity occurs between trichodorid vector species and tobravirus serotypes. This specificity was more apparent with associations betweenParatrichodorusvector species and tobravirus serotypes than with those betweenTrichodorusspecies and tobravirus serotypes.P. pachydermustransmitted PRN‐serotype tobacco rattle virus (TRV) isolates,P. teresORE‐serotype isolates andP. anemonesTRV isolates which did not react with any of the antisera used, but which could be distinguished from all other isolates by their symptomatology inChenopodiumtest plants.T. viruliferus, T. primitivusandT. cylindricustransmitted RQ‐serotype isolates and the latter species also transmitted TRV isolates reacting with TCB2 and pea early‐browning SP5‐antisera. Several TRV isolates transmitted byT. cylindricusfailed to react with any of the anti

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03471.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryIn field plots at Yancheng, Jiangsu, China, a range of European and Asian barley cultivars was grown in soil from three sites in China infested with barley yellow mosaic virus (BaYMV). Most of the cultivars resistant to the common European strain of BaYMV were susceptible to the Chinese isolates but cv. Energy remained disease‐free. Barley mild mosaic virus (BaMMV) was also detected in one of these soils but affected only one Chinese cultivar and not those susceptible to BaMMV in Europe. This is the first report of BaMMV in China.Inoculation experiments confirmed the different cultivar response to UK and Chinese isolates of BaYMV and showed that resistance was to the virus and not to the vector. A range of Chinese cultivars selected for resistance to BaYMV were also resistant to a UK isolate of BaMM

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03472.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryMaize streak virus (MSV) capsid antigens were detected over time in different parts of maize plants of a sensitive (INRA508) and a so‐called tolerant (“tolerant”) cultivar (IRAT297) using a direct or an indirect double antibody sandwich ELISA. Based on three types of experiments, it was shown that the antigens were distributed in the plant according to the age of the tissues. When the virus was inoculated on a particular leaf of 18‐day old plants with infectiveCicadulina mbila, only the young leaves above the inoculated one were positive by ELISA but not the older ones below. The antigens could not be detected in the inoculated leaf. At day 3 after inoculation, the antigens were detected in the sheath and/or in the whorl of the third leaf above the inoculated one but not in the oldest part of the leaf, the unfolded lamina. Plants of the sensitive cultivar were inoculated at 9 days withC. mbiladeposited in the whorl. At 23 h after inoculation, the antigens were detected in the sheath but not in the whorl which was found to be positive only at 32 h. On the basis of these results, a hypothesis of the mode of virus infection is proposed. Our results contribute to a better understanding of the relationship between the age of the plant at inoculation and yield loss as well as secondary infection. By transmission tests withC. mbila, it was shown that virus could only be acquired from leaves exhibiting symptoms. Virus concentrations were measured in plant samples by ELISA using a range of dilutions of purified virus. The virus concentrations were higher in the sensitive than in the “tolerant” cultivar, but no difference in antigen distribution was observed between the two cultivars. The “tolerant” cultivar appeared to be resistant to virus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03473.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThree formulations of diazinon: flowable granules (FG); wettable powder (WP); and emulsifiable concentration (EC), which are used for the control of mushroom pests, were compared for toxicity towards a hybrid and non‐hybrid strain of the cultivated mushroom,Agaricus bisporus.With all formulations, yield and number of mushrooms were reduced according to dosage (linear trend). The EC was the most toxic and persistent formulation – equally so to both mushroom strains – and produced the most severe responses in all the parameters considered. The WP was the least toxic formulation. The hybrid strain was more susceptible to diazinon than the non‐hybrid, but not mark

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03474.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe dose responses of 14 wild plant species (two grasses, two legumes, one annual and nine perennial dicotyledons), not usually recognised as weeds, to four herbicides (asulam, glyphosate, MCPA and mecoprop) were measured in glasshouse experiments. Glyphosate was the most toxic; seven of the species tested had EDu, values (measured as shoot dry weight) of<1.0 μg/plant, compared with only one species for MCPA and mecoprop. Asulam was the least toxic.Results were used to indicate the risk to each species from drift damage. A model of spray drift, based on that developed by Thompson&Ley (1982) for evaporating droplets, was rescaled to allow for field application rates and used to predict the distances travelled by given doses of herbicide. This gave acceptable agreement with reports for drift damage in the field, and predicted that only glyphosate sprayed at the highest recommended concentration might be unsafe to some of the species examined. The two herbicides sometimes used as volatile formulations (MCPA and mecoprop) did not cause damage at the small doses likely to result from exposure to vapour in the field

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb03475.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY