摘要:

AbstractInfection of hop plants with hop stunt viroid (HSV) results in the retardation of the growth rate except for the rate of leaf emergence and the disappearance of the fold‐like structure over the epidermal cell. Mature cones from HSV‐infected hop plants remained small‐sized and the content of α‐acid was half to one third of that of HSV–free hop cones. In HSV‐infected hop cones, the lupulin glands are distributed most abundantly on the bracteoles and the perianths and their numbers are reduced by at least 60% of that in the HSV‐free control. Scanning electron micrographs confirm that most of the lupulin glands on bracteoles from HSV‐infected hop cones shrivel severely, but not those from HSV‐free hop cones. They also reveal that the lupulin glands on the perianths from both, HSV‐free and HSV–infected hop cones become withered. Moreover, spherical granules (1.2 to 1.9μm in diameter) were not observed on the surface of the lupulin glands from

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1984.tb00734.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractSurvival period and possibility of seed transmission ofX. campestrispv.oryzaewere studied. The bacterium survived for longer (170–180 days) in kharif than rabi (120–130 days) harvested seed. The percentage of infected seeds was higher in kharif than rabi. The infected seed when sown failed to produce the symptoms on respective seedlings due to the low number of bacterial population. Present studies indicated that infected seed though may not produce symptoms on the seedlings directly but serve as a source of inoculum form season to sea

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1984.tb00735.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractEssential Oils fromOcimum basilicumand their components showed different inhibition effects againstFusarium oxysporumf. sp.vasinfectumandRhizopus nigricans, The different antifungal activity of the essential oils is determined mainly by the percentage of the main components: cineol, linalool, methylchavicol and eugenol.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1984.tb00736.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe effect of genes for resistance against powdery mildew of barley was determined microscopically in stained leaf segments 44 h after inoculation and compared with the visual was established between the number of haustoria and the visual disease symptoms. Deviations were expressed after C17 Am inoculation of the mutant B682, which exhibited low infection grade although high numbers of haustoria were formed; thus the induced resistance gene of B682 is expressed only in later stages of the infection process. On the other hand, after inoculation of SR1 with theml‐ovirulent isolate HL3 high infection grade was measured following low haustoria numbers; obivously, this isolate is able to grow more intensively after first haustoria have been formed.Consequently, the close relation between haustoria numbers and infection grade is reestablished in the double mutants under HL3 infection. The implications of this finding for resistance breeding are discusse

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1984.tb00737.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractSporulation of the rust fungusUromyees phaseoliwas checked on three different Brasilian bean cultivars on the upper and lower leaf surface of primary leaves in a growth chamber at 21°C. Although the sporulating area of the pustules was greater on the upper leaf surface, the pustules on the lower leaf surface produced nearly two times more spores on all three cultivars.The total number of spores produced per pustule was 41,600/81,000 spores (upper/ lower leaf surface) for the susceptible cultivar Rosinha G‐2/C‐21 and for the cultivars which possess horizontal resistance: Carioca/C‐224 29,600/49,500 spores (upper/lower leaf surface), Roxo/C‐743 32,964/50,700 spores (upper/lower leaf surface). The two cultivars with horizontal resistance produced nearly a third less spores than the susceptible

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1984.tb00738.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractUltraviolet light (UV) irradiation increased expansion of TMV lesions in detached Pinto bean primary leaves incubated in darkness. However, if after UV‐irradiation the leaves were incubated in the light, no increase in lesion expansion occurred. The light effect was considered not to be due to photorepair of UV damaged DNA, since non‐photorepairing treatments such as incubation in red light, or delayed exposure to white light after UV irradiation also prevented increase in lesion expansion. The effect of visible light in preventing TMV‐lesion enlargement was shown to be related to photosynthetic energy supply to the host cell defense mechanism since incubation of infected leaves in the presence of the photosynthesis inhibitor 3‐(3,4‐dichlorophenyl)‐l,l‐dimethyl urea (DCMU) in light caused large lesions whether leaves were irradiated by UV or not. Supplying 0.1 M sucrose in the dark also inhibited lesion enlargement in UV‐irradiated or nonirradiated leaves. Dinitrophenol (DNP) negated the sucrose effect in the dark. However, in light incubation, DNP did not induce large lesions indicating that DNP did not interfere with energy supply in the light.It is concluded that the Pinto bean leaf cells can use energy derived both from mitochondria and chloroplasts for building the resistance mechanism to virus spread. In this case, cellular resistance to virus spread seems to be correlated with callose deposition on the walls of noninfected cells adjacent to the necrotic cells. Energy supply in various forms will assist host cells in building the resistance mechanism as well as retarding senescence. Detachment, prolonged dark incubation, or exogenous supply of DNP led to accelerated senescence which in turn led to secondary enlargement of lesions. The cause of such secondary enlargement may be explained by starvation of cells and disappear

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1984.tb00739.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractInvestigations on the production of extracellular hemicellulases byPseudocercosporella herpotrichoides in vitroFor all 15 isolates ofPseudocercosporella herpotrichoidesinvestigated, xylanase as well as arabanase activity could be demonstrated. After cultivation of 3 weeks, the activity of the enzymes reached a peak. The activity of xylanase was considerably increased by addition of xylan in comparison to Maltzin as the sole source of carbohydrate. Also the arabanase activity could be increased significantly by addition of araban or xylan as compared to the Maltzin variant.The optimum temperature with regard to activity and stability of xylanase ranged at 50°C. The pH‐optimum for xylanase activity was found to be at pH 5.0, and the enzyme was stable in ° range between pH4.0 and 8.0 (9.0). In case of arabanase, the temperature optimum varied between 40 and 50°C; up to this temperature, the enzyme was also stable. At pH 5.0, the arabanase activity reached its optimum; stability was observed in ‐ pH range between 4.0 and 9.0.In extracts prepared from autoclaved wheat coleoptiles which were inoculated withPseudocercosporella herpotrichoides, the presence of the enzymes xylanase, arabanase, cellulase and polymethylgalacturonase could be demonstrated. The enzyme activities of the inoculated samples were considerably higher than those of non‐inoculated controls. The differences, in most cases, were statistically significant.Der Deutschen Forchungsgemeinschaft danken wir für finanzielle Unte

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1984.tb00740.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractPulse xanthomonads could not be differed on the basis of their bacteriological propertries. Colonies from cowpea, mungbean, guar, and bean showed differences in virulence related to the degree of mucoidness than to the rate of multiplication. Very weakly virulent mutants of the bean fuscous pathogen produced distinctive reaction in bean pods. White mutants were as virulent as their yellow forms.

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1984.tb00741.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractSignificant differences were observed among 11 alfalfa cultivars for the percentage of plants resitant toLeptospbaerulina briosianaafter one inoculation. Screening for resistance was done by inoculating 18 day old plants (cv. Europe), held in a moist chamber, withL. briosiana. The self‐ and cross‐progenies of plants resistant toL. briosianaafter two inoculations showed slightly higher resistance to Leptosphaerulina leaf spot than the unselected original population but the difference was significant for the cross‐progeny only. Larger variations were observed among self‐progenies than cross‐progenies. No correlation was found between self ‐ and cross‐progenies. At least three inoculations may be necessary to eliminate most susceptible plants.Mas selection was as effective as the polycross progeny test to improve the level of resistance of the selected populations as compared with the unselected one but the difference was agronomically unimportant.Under field conditions, the plants selected as resistant after two inoculations in the laboratory showed better resistance toL. briosianathan the susceptible ones but only on the first of three notations. The population derived from plants selected from cv. Europe as resistant toL. briosianain the laboratory was not significantly more resitant than cv. Europe in the filed but generally showed less fol

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1984.tb00742.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractQuantitative changes of individual phenolic acids in rust‐infected groundnut leaves were studied at various stages of disease development. There was no qualitative change in the phenolic acids. However, the concentration of the phenolic compounds increased due to infection more particularly of chlorogenic andtransandciscaffeic acid

ISSN:0931-1785    

DOI:10.1111/j.1439-0434.1984.tb00743.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY