Journal of Phytopathology
0931-1785
1439-0434
Anh Quốc
Cơ quản chủ quản: Wiley-Blackwell Publishing Ltd , WILEY
Lĩnh vực:
PhysiologyGeneticsAgronomy and Crop SciencePlant Science
Các bài báo tiêu biểu
Population Genetics of Three Important Head Blight Pathogens <i>Fusarium graminearum, F. pseudograminearum</i> and <i>F. culmorum</i> Abstract Homothallic Fusarium graminearum (teleomorph Gibberella zeae ) and anamorphic F. culmorum are destructive pathogens causing Fusarium head blight (FHB) of small‐grain cereals worldwide, while heterothallic F. pseudograminearum (G. coronicola ) seems to be restricted to Australia as a FHB pathogen. In a comprehensive treatise of pathogen population genetics, this review summarizes global knowledge of genetic diversity among isolates sampled at various spatial and temporal scales, examines the mechanisms that generate this diversity and explores the implications of pathogen diversity and plasticity to resistance breeding. Despite their different modes of reproduction, there is large variation among isolates of all three species originating from different countries and continents. With a few exceptions, haplotype diversity ranges from 60 to 100% even within populations from individual fields. In F. graminearum , over 90% of the variation is found within populations, even when samples are collected from areas as small as 0.25 m2 . Variation among populations is low (4–8%) with negligible population subdivision. This indicates a high level of gene flow (N m = 8–71) with linkage equilibrium for the majority of selectively neutral molecular marker loci analysed. These findings for F. graminearum point to large random mating populations driven by occasional outcrossing, high gene flow across large geographical distances and a relatively low host‐mediated directional selection. Similar conclusions can be drawn for the Canadian population of F. pseudograminearum , but not for populations from Australia, where different pathogen ecology may have reduced the frequency of sexual recombination. Phylogenetic analyses indicate delineation of lineages in F. graminearum , often along geographically separated lines, while the related F. pseudograminearum is a single recombining species with limited or no lineage development. The anamorphic F. culmorum shows no obvious clonal structure in its population as might have been expected. High levels of diversity within fields may have been caused by balancing selection from frequent alternation between saprophytic and parasitical life cycle and/or a hidden or recently extinct teleomorph. Other mechanisms including parasexual cycles or active transposable elements may also be involved but these have not been investigated as yet. Crosses between and among F. graminearum lineages have shown a rather simple, additive inheritance of pathogenicity and aggressiveness with frequent transgressive segregation in crosses among isolates with moderate aggressiveness. This raises the spectre of highly aggressive and/or toxigenic isolates evolving if a limited range of quantitative trait locus for FHB resistance is deployed on a large scale. Combining more than one genetically distinct sources of resistance, possibly with different modes of action against the pathogen, will be necessary to avoid severe FHB outbreaks in the future.
Tập 156 Số 3 - Trang 129-139 - 2008
Gas Exchange and Emission of Chlorophyll Fluorescence during the Monocycle of Rust, Angular Leaf Spot and Anthracnose on Bean Leaves as a Function of their Trophic Characteristics Measurements related to gas exchange and chlorophyll fluorescence emission were taken from healthy and diseased bean leaves with rust, angular leaf spot, and anthracnose during lesion development for each disease. The experiments were performed at different temperatures of plant incubation, and using two bean cultivars. The main effect of temperature of plant incubation was in disease development. There was no significant difference between cultivars in relation to disease development and in magnitude of physiological alterations when disease severity was the same for each cultivar. These diseases reduced the net photosynthetic rate and increased the dark respiration of infected leaves after the appearance of visible symptoms and the differences between healthy and diseased leaves increased with disease development. The transpiration rate and stomatal conductance were stable during the monocycle of rust, however, these two variables decreased in leaves with angular leaf spot and anthracnose beginning with symptom appearance and continuing until lesion development was complete. Carboxylation resistance was probably the main factor related to reduction of photosynthetic rate of the apparently healthy area of leaves with rust and angular leaf spot. Reduction of the intercellular concentration of CO2 , due to higher stomatal resistance, was probably the main factor for leaves with anthracnose. Chlorophyll fluorescence assessments suggested that there was no change in electron transport capacity and generation of ATP and NADPH in apparently healthy areas of diseased leaves, but decreases in chlorophyll fluorescence emission occurred on visibly lesioned areas for all diseases. Minimal fluorescence was remarkably reduced in leaves with angular leaf spot. Maximal fluorescence and optimal quantum yield of photosystem II of leaves were reduced for all three diseases. Bean rust, caused by a biotrophic pathogen, induced less damage to the regulation mechanisms of the physiological processes of the remaining green area of diseased leaves than did bean angular leaf spot or anthracnose, caused by hemibiotrophic pathogens. The magnitude of photosynthesis reduction can be related to the host–pathogen trophic relationships.
Tập 150 Số 1 - Trang 37-47 - 2002
The Susceptibility of Monocotyledons to Agrobacterium tumefaciens Abstract The susceptibility of 257 monocotyledon species belonging to 139 genera and 27 families, has been tested and the literature on this subject reviewed. In contrast with dicotyledons and gymnosperms, monocotyledons are much less susceptible to Agrobacterium tumefaciens : only 3 % of the species of monocotyledons tested were host plants, whereas 60 % of the dicotyledons and gymnosperms were susceptible. Only the closely related monocotyledon orders Liliales (6 families) and Arales (1 family) contained species that were susceptible. These results are consistent with a proposed taxonomic relationship between the Liliales and the dicotyledons. A correlation between host biochemical capabilities and susceptibility to crown gall is suggested.
Tập 113 Số 1 - Trang 81-89 - 1985
Antifungal Activity of a Bowman–Birk‐type Trypsin Inhibitor from Wheat Kernel A trypsin inhibitor from wheat kernel (WTI) was found to have a strong antifungal activity against a number of pathogenic fungi and to inhibit fungal trypsin‐like activity. WTI inhibited in vitro spore germination and hyphal growth of pathogens, with protein concentration required for 50% growth inhibition (IC50 ) values ranging from 111.7 to above 500 μg/ml. As observed by electron microscopy, WTI determined morphological alterations represented by hyphal growth inhibition and branching. One of the fungal species tested, Botrytis cinerea produced a trypsin‐like protease, which was inhibited by the trypsin inhibitor. WTI, as well as other seed defence proteins, appear to be an important resistance factor in wheat kernels during rest and early germination when plants are particularly exposed to attack by potential soil‐borne pathogens.
Tập 148 Số 7-8 - Trang 477-481 - 2000
Resistance to Pyrimethanil and other Fungicides in <i>Botrytis cinerea</i> Populations Collected on Vegetable Crops in Spain Abstract Forty‐seven greenhouses of vegetable crops were surveyed in south‐eastern Spain at the beginning of the epidemic (January 2000) to compare sensitivity of Botrytis cinerea populations to pyrimethanil (an anilinopyrimidine fungicide) after 4 years of treatment with an unexposed population from a 1992 collection. A standard method to test the sensitivity of B. cinerea to pyrimethanil in a defined minimal medium (1.75 g/l of KH2 PO4 , 0.75 g/l of MgSO4 , 4 g/l of glucose and 4 g/l of gelatine) was used to establish frequency distributions of pyrimethanil sensitivity in both populations. Two different distributions for sensitive and resistant isolates were obtained. ED50 of sensitive isolates in 1992 ranged from 0.05 to 0.5 mg a.i./l (mean ± SE, 0.23 ± 0.02), and 0.04–0.4 mg a.i./l in 2000 (0.11 ± 0.01). ED50 for resistant isolates ranged from 1 to 10 mg a.i./l in both surveys (5 ± 2.64 and 4.25 ± 2.14, in 1992 and 2000, respectively). No resistance build‐up to pyrimethanil was developed in B. cinerea populations after exposition of 4 years to the fungicide. An in vitro monitoring procedure was developed based on testing on one single discriminatory dose of pyrimethanil (established at 0.7 mg a.i./l). Isolates resistant to pyrimethanil in the in vitro assay caused visible lesions on cucumber leaf discs treated with the fungicide. No significant differences in fitness (growth or sporulation) between resistant and sensitive isolates were obtained. The 307 isolates collected in January 2000 were tested in vitro using discriminatory doses to estimate the frequencies of resistance of B. cinerea to benzimidazoles (carbendazim), dicarboximides (procymidone), N ‐phenylcarbamates (diethofencarb), and anilinopyrimidines (pyrimethanil). Of the 307 isolates collected, 90% were resistant to benzimidazoles, 77% to dicarboximides, 23% to N ‐phenylcarbamates and 12% to anilinopyrimidines (in this case of 165 isolates). Dicarboximide and benzimidazole cross‐resistant isolates were found in each of the surveyed greenhouses and accounted for 65.8%. Fourteen percentage of the population were resistant to dicarboximides, benzimidazoles and N ‐phenylcarbamates, and 3% were also resistant to anilinopyrimidines.
Tập 152 Số 8-9 - Trang 484-490 - 2004
Scanning Electron Microscopy of <i>Pseudomonas syringae</i> pv, <i>morsprunorum</i> on Sweet Cherry Leaves Abstract Scanning electron microscopy indicated that sub‐stomatal cavities on sweet cherry leaves are “protected sites” which shelter resident populations of Pseudomonas syringae pv. morsprunorum . Bacteria entered the stomata, multiplied in the cavities and emerged in a mass 6 days after inoculation. There were no visible symptoms, suggesting that the pathogen colonized the host in “sub‐clinical” numbers to generate populations which were then released onto the leaf surface under suitable conditions.
Tập 108 Số 1 - Trang 18-25 - 1983
Feeding and Transmission Characteristics of Aceria tulipae Keifer as Vector of Wheat Streak Mosaic Virus)
Tập 55 Số 3 - Trang 218-238 - 1966
Drying of Conidia of <i>Penicillium oxalicum</i>, a Biological Control Agent against <i>Fusarium</i> Wilt of Tomato Abstract The effects of freeze drying, spray drying, and fluid bed drying on the viability of Penicillium oxalicum conidia were compared. Conidia of P. oxalicum can be dried by fluid bed drying and freeze drying maintaining 100% viability after both processes, but protective additives must be added for obtaining this viability in the case of freeze drying. The best viabilities were obtained after freeze drying with non‐fat skim milk (NFSM) + Tween 20, NFSM + peptone and NFSM + sucrose. However, NFSM + glycerol had only a 0.5% viability after freeze drying. Freeze‐dried P. oxalicum conidia with or without additives did not maintain viability over time at room temperature, while conidia dried in a fluidized bed drier had a 40–50% viability after 180 days of storage in these conditions. Penicillium oxalicum conidial viability after spray‐drying was lower than 20%. Penicillium oxalicum conidia dried by fluid bed drying were effective in reducing the incidence of Fusarium wilt of tomato under glasshouse and field conditions.
Tập 151 Số 11-12 - Trang 600-606 - 2003
Spread of Agrobacterium tumefaciens in the Vessels of the Grapevine, after Natural Infection
Tập 63 Số 3 - Trang 239-246 - 1968
Use of an Immunocapture‐Polymerase Chain Reaction Procedure for the Detection of Grapevine Virus A in Kober Stem Grooving‐Infected Grapevines Abstract Reliable and highly sensitive detection of grapevine virus A (GVA) in grapevine leaf tissue by reverse transcription‐initiated polymerase chain reaction was achieved after enrichment and partial purification of the virus from grapevine crude sap by an immunocapture (IC) procedure. In comparison with ELISA the gain of sensitivity was estimated up to 1000‐fold in grapevine mature leaf tissue. Using IC‐reverse transcription polymerase chain reaction (IC‐RT‐PCR), GVA could be detected in very young grapevine tissue where the virus titre was largely below the detection limit of ELISA. The comparison of IC‐RT‐PCR and biological indexing results for about 60 grapevine accessions revealed a good correlation between the presence of GVA and the development of Kober stem grooving (KSG) symptoms in the specific indicator rootstock Kober 5BB. Moreover, the elimination of KSG by heat treatment in two Vitis vinifera cultivars, Savagnin rose and Servant, was accompanied by the loss of detection of GVA by PCR, thus providing further argument for the involment of GVA in the aetiology of KSG.
Tập 143 Số 6 - Trang 369-373 - 1995