摘要:

AbstractStreptomyces griseusproduces an antibiotic substance againstColletotrichum lindemuthianumbecause, in dual culture on potato dextrose agar (PDA), a large inhibitory zone was formed between the colonies ofS. griseusandC.lindemuthianum. WhenS. griseuswas placed adjacent to a colony ofC. lindemuthianumin PDA,S.griseusgrew poorly in PDA but it thrived and sporulated profusely when it came in contact with a colony ofC. lindemuthianumindicating thatS.griseusmight require some essential nutrients fromC.lindemuthianum. Scanning electron microscopy showed that hyphae ofS.griseusin contact withC.lindemuthianumproduced appressorium‐like swellings or simply grew on the hyphal surface ofC.lindemuthianum. Internal parasitism was evidenced by the presence of hyphae and conidia of the mycoparasite inside the host hyphae. Internal parasitism resulted in formation of several blebs. Cell walls of the parasitized hyphae degenerated having a sponge‐like texture. The blebs broke off and left rounded holes on the hyp

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00960.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractSix commercial carnation cultivars were inoculated withFusarium oxysporumf. sp.dianthirace 2, and grown under three different temperature regimes. Colonization by the pathogen and development of wilt symptoms were assessed at intervals up to 40 days. No symptoms and very little colonization were seen in any of the cultivars at 14–15°C. At a temperature of 22°C, the cultivars were clearly differentiated into three groups: those with resistance, partial resistance or susceptibility to the pathogen depending on the severity of symptoms and the extent of fungal colonization. Symptom severity was associated with the extent of colonization. This differentiation was not seen at 26°C, when all cultivars except the most resistant, cv.‘Carrier 929′, rapidly became diseased and died by 23 days after inoculation. ‘Carrier 929’ also showed some wilt symptoms at this temperature and was colonized throughout the height of the stem after 40 days. The pathogen caused disease at 26°C by a combination of vascular wilting and stem base and root rotting.Fungal colonization was assayed at 22°C by the dilution plate/homogenization method and by estimation of fungal chitin in a highly resistant (‘Carrier 929′) and in a highly susceptible (‘Red Baron’) cultivar. Both methods of assay gave similar results. In ‘Red Baron’, colonization increased slowly up to 20 days after inoculation then progressed rapidly, closely following the development of severe wilt symptoms. In ‘Carrier 929’, colonization remained very low. The low level of fungal biomass in ‘Carrier 929’ compared with ‘Red Baron’ indicated that the former cultivar showed true resistance

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00961.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA low‐molecular weight double‐stranded (ds) RNA [900 base pairs (bp)] associated with groundnut rosette disease can be used as a diagnostic tool. A simple procedure has been developed that is rapid, reliable, and requires only standard electrophoresis equipment and ultraviolet light for detection of nucleic acid bands. Using this procedure, the dsRNA was detected only in groundnut plants with green rosette of chlorotic rosette symptoms. It was not found in uninoculated groundnut plants, in symptomless groundnut plants with groundnut rosette assistor virus, or in groundnut plants infected with several other known groundnut viruses. In studies with northern blots of extracts from rosette‐diseased and healthy plants, 5′‐endlabeled dsRNA only hybridized to a 900 bp dsRNA from diseased plants. The 900 bp dsRNA was not infectious and its origin remain

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00962.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe feasibility of use of lupins, oats and field peas as alternative rotation crops to reduce inoculum of the take‐all fungus (Gaeumannomyces graminisvar.tritici) (under Western Australian field conditions) and disease in following wheat was investigated with a one year field trial, the soil from which was used in two succeeding pot experiments. The possible mechanisms of reduction of inoculum and disease by these crops were examined testing the soil for pathogen and disease suppression. Rotation with lupins or oats for two seasons reduced (P<0.05) inoculum of the take‐all fungus and lupins, oats or field peas reduced (P<0.05) disease in following wheat. Lupins alone reduced inoculum and disease, (P<0.1) after one season. No apparent suppression of the pathogen in the absence of host plants was recorded after one season of rotation, but after two seasons, lupins, oats or field peas all suppressed (P<0.02) growth of the pathogen within soil. However only field pea soil suppressed take‐all in comparison with the wheat control.Although after two seasons all rotation crops were effective in reducing inoculum and disease the mechanisms of reduction appear to differ between the rotation crops used in this

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00963.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractPopulations of pathogenicPseudomonas syringaepv.syringaewere monitored on apparently healthy leaves, blossoms, and fruit from two apple orchards with known histories of blister bark and a pear orchard with a known history of blossom blast. Populations on blossoms and fruits were higher on pears than on apples. Yellow‐pigmented, non‐pathogenic bacteria might have suppressed or masked the presence ofP. syringaepv.syringaeon apple trees. Populations ofP. syringaepv.syringaeon apple and pear leaves fluctuated sharply but higher levels generally occurred during the 1984/85 growing season than during the drier 1983/84 season. This investigation indicates that the resident phase ofP. syringaepv.syringaeis probably a major source of inoculum for apple blister bark and pear blossom blast in South Afr

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00964.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThin sections of midribs from aFragaria vescaUC‐5 indicator plant infected by leaf grafting with a German isolate of strawberry crinkle contained typical rhabdovirus‐like particles within cytoplasmic vesicles. Masses of rhabdovirus‐like particles with a dark stained core and a transparent surrounding layer were seen in necrotic cells surrounding the vascular bundle and in necrotic leaf paren

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00965.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractControlled environment studies revealed significant genetic variation in resistance of wheat seedlings toFusarium culmorumby using a new developed test system which affords a reproducible inoculation and a precise measurement of the infection rate. A nutrient solution and a conidial suspension in a defined amount are added to agar after autoclaving and the germinated seed are incubated under sterile conditions. With thisin vitro‐culture techniqueF. culmoruminfected the whole root system of all tested plants during 12 days and caused significant reduction of root and shoot dry weights. Therefore, escape reactions, depending on the different rapidity of root development, were eliminated. The loss of root dry matter ranged from 12 to 89 %, thus allowing a selection forFusariumresistance even in the early developmental stages of whea

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00966.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA virus reported earlier to cause a green mosaic disease of eggplant in Nigeria was studied in more detail. Its filamentous particles with a normal length of 820 nm reacted in immunoelectron microscopical tests strongly with the homologous antiserum and less strongly with antisera to dioscorea green banding mosaic, groundnut eyespot, zucchini yellow mosaic viruses and to a tomato potyvirus isolate from Taiwan. No reactions were seen with antisera to 25 other potyviruses. Several new host plants were identified. Infected cells contained cylindrical inclusions with scrolls and short curved laminated aggregates and clusters of small vesicles with electron‐dense content. Host range and serological reactivities differentiate the virus for which the name eggplant green mosaic virus is suggested from all potyviruses so far know

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00967.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAn enzyme‐linked immunosorbent assay (ELISA) was developed for the coryneform bacterium isolated from ratoon stunted surgarcane. Parameters governing the ELISA were optimized. These included antibody coating concentration, conjugate concentration and diluent, antigen diluent, the washing procedure, incubation temperature for sample and conjugate, pH and time. The level of detectability of the cultured bacterium by the ELISA was ≥ 1 × 104Zellen ·

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00968.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe sclerotia ofSclerotium rolfsiiSacc. survived in natural soil for 225 days under controlled moisture at 50% water holding capacity (WHC) after which there was a progressive reduction in the population of viable sclerotia. At 390 days only 48% were recovered. Sclerotia survived well at moisture contents upto 75% WHC but at 100% the population declined rapidly and none were recovered after 60 days. The contents of the sclerotia were found to lyse without germination leaving hollow rinds. Such lysis was found to be favoured between 25 and 40°C. At and below 20°C no such lysis was recovered and more than 80% sclerotia were recovered even after 60 day

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1988.tb00969.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY