摘要:

AbstractCocoyam is the second most important staple crop of Cameroon and root rot is a destructive disease of this plant.Pythium myriotylum(Pm),Fusarium solani(Fs), andRhizoctonia solani(Rs) were isolated from the rhizosphere of root rot affected cocoyams and from the soil of a cocoyam experimental field plot temporarily devoid of same in Mamu, Cameroon. Pm was isolated from the above soil by the cocoyam leaf disc baits. Fs and Rs were also isolated from the same soils by the water dilution method and from the roots of diseased cocoyams but were always associated with mycelial growth of Pm. Pathogenicity of Pm and in combinations with Fs or Rs or Fs + Rs all developed cocoyam root rot disease (CRRD) symptoms on 3– and 7–month old cocoyam plantlets 2–7 days after inoculation. Symptoms included rotted roots and wilting with general chlorosis of inoculated plantlets. No symptoms of CRRD were noted on cocoyam plantlets inoculated with Fs, Rs, Fs + Rs, and distilled water. Results indicated that CRRD is not caused by several pathogens but only by Pm. Pm isolates from the soils and roots of diseased cocoyams and those maintained in the ROTREP laboratory have significantly bigger diameter of mycelial colony growth in 24 h–period at 31 °C on lima bean sucrose agar, V–8 juice sucrose agar, and potato sucrose agar than on potato dextrose agar and 2 % water agar. The cocoyam plantlets were raised axenically from tissue culture of explants in the

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb04312.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractInoculation of apple seedlings with the mycorrhizal fungusGlomus mosseaesignificantly increased their growth in apple replant disease soil that was neither pasteurized nor fertilized with monoammonium phosphate. The application ofEnterobacter aerogenesand peat suppressed the stunting effect observed in apple replant disease soil. These results suggest the potential of using G.mosseaealone or a E.aerogenesand peat combination for the control of apple replant disease.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb04313.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractApigmented bacterial colonies were obtained in Reunion Island from angular leaf lesions on Pepper tree (Schinus terebenthifoliusRadii), a member ofAnacardiaceae. All isolates were identified asXanthomonas campestris, using physiological and biochemical tests.These strains were reinoculated to Pepper tree leaves, and Koch postulates were verified. Furthermore, they were inoculated to mango leaves and produced lesions identical to those induced byXanthomonas campestrispv.mangiferaeindicae, the causal agent of bacterial black spot of mangoes. Apigmented and pigmented strains ofX. c.pv.mangiferaeindicaefrom Mango and Ambarella were pathogenic to Pepper tree.Strains isolated from Pepper tree were compared toX. c.pv.mangiferaeindicae, by means of phenotypic features (utilization of 147 carbon sources) and using a serological assay. A high homology among the strains was observed.Thus, It is concluded that strains isolated from Pepper tree belong to pv.mangiferaeindicae, and that Pepper tree is a host species forX. c.pv.mangiferaeindicae.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb04314.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe Indian cassava mosaic virus (ICMV) was transmitted by the whiteflyBemisia tabaciand sap inoculation. ICMV was purified from cassava and from systemically infectedNicotiana benthamianaleaves. Geminate particles of 16–18 × 30 nm in size were observed by electron microscopy. The particles contained a single major protein of an estimated molecular weight of 34,000. Specific antiserum trapped geminate particles from the extracts of infected cassava andN. benthamianaplants in ISEM test. The virus was detected in crude extracts of infected cassava, ceara rubber, TV.benthamianaandN. tabacumcv. Jayasri plants by ELISA. ICMV appeared serologically related to the gemini viruses ofAcalyphayellow mosaic, bhendi yellow vein mosaic, Croton yellow vein mosaic,Dolichosyellow mosaic, horsegram yellow mosaic,Malvastrumyellow vein mosaic and tobacco leaf cu

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb04315.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractStagonospora apocynicauses a leaf spot disease on hemp dogbane (Apocynum cannabinumL.). The fungus produced phytotoxins citrinin, mellein, tyrosol and α–acetylorcinol in liquid culture. All toxins caused necrosis when placed on leaves of hemp dogbane, and eight other weed species. All four toxins were non–specific phytotoxins. Citrinin showed antimicrobial properties against some bacteria and f

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb04316.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA histological study was made of the systemic growth ofBotrytis cinereafrom styles, stamens and sepals to the flower receptacle and mesocarp of immature pear fruit. In most styles, hyphal growth ceased in the upper portion at the onset of stylar senescence, which occurred at about 1 wk after full bloom. Hyphae never passed through styles into the carpel. Unlike the styles, hyphae in filaments grew without restriction and progressed within 4 days, via vascular tissue, through sepals into tissues of the upper end of the flower receptacle, or of the mesocarp adjoining the sepals, without causing symptoms. Filaments remained green to partly green until harvest.B. cinereaentered filaments and spread into the receptacle or mesocarp at any time between blossoming and harvest and then became latent in these tissues. Filaments were, however, more susceptible at the flowering stage. After 2 months floral tubes were closed, and the stamens protected from infection. Careful inspection of ripe, cold–stored fruit showed that decay invariably spreads from mesocarp tissue adjoining the sepals, outward along the vascular bundles, but not from secondary inoculum in the floral tube. The behaviour of the pathogen suggests that control of blossom–end rot could be achieved if pears are sprayed with fungicide at 75—100% petal fall (when most stamens are exposed) and a month later (before floral tubes started to c

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb04317.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe relationship between pre–flowering climatic conditions and sugary disease incidence m sorghum was quantified over two seasons. In field trials with three male normal genotypes, low night temperatures 3—4 weeks prior to flowering increased susceptibility to the disease. Average night temperatures of<12 °C during the critical period resulted in male–normal genotypes being as susceptible as male–sterile genotypes. Seed set in uninoculated heads under pollination bags was also reduced, suggesting that increased susceptibility was the result of low temperature induced sterility. Genotypes differed in their ability to tolerate pre–flowering cold stress. Greenhouse and growth chamber trials confirmed that cold stress applied 7—8 weeks after planting reduced pollen viability and that this was the primary reason for increased susceptibility to su

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb04318.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe infection of lentil roots byFusarium oxysporumSchlecht and the responses of the host cells to invading hyphae were examined by light microscopy. Hyphae from inoculum placed on the zone of cell elongation entered the roots at the juncture of epidermal cells within 8 h after inoculation. Although swollen hyphal apices were observed on the epidermal cells, root penetration occurred without formation of these structures or appressoria. The sheath of material found on the surface of uninoculated roots was absent from inoculated roots penetrated by hyphae. Prior to penetration, the epidermal cells became irregular in shape and their cytoplasm appeared to be plasmolysed or granular. Hyphae were observed in the cortex 10—12 h after inoculation and non–penetrated cortical cells were distinctly lobate. Often these lobed cells had a broad, peripheral band of diffuse cytoplasm. When hyphae were first observed in the cortical cells, the walls were ruptured and only slightly stained or unstained by toluidine blue. The inability of such walls to bind the stain may have been the result of the removal of wall components by fungal enzymes.Although extensive proliferation of hyphae was evident throughout the cortex after 24 h of incubation, the endodermis and vascular cylinder were free of hyphae for at least 72 h. Hyphae from inoculum placed on the root hairs or the root apex failed to penetrate the roots during the first 24 h of incubation.The cytological results herein are discussed in relation to the infection of field plantings by this patho

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb04319.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Book Reviwed in this article:Diercks, R., und R. Heitefuß (Hrsg.), Integrierter Landbau. Systeme umweltbewußter Pflanzenproduktion. Verlagsunion Agrar/BLV Verlagsges.Lycett, G. W., Grierson, D. (eds): Genetic Engineering of Crop Plants.Whipps, J. M., and R. D. Lumsden (eds), Biotechnology of fungi for improving plant growt

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1992.tb04320.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY