Plant Sci. We investigated the host-mediated interaction between the biotroph Blumeria graminis f. Both diseases are potentially severe in humid temperate climates and are controlled by fungicides and by growing wheat varieties with partial resistance. The compatible interaction between Z. The effect on virulent Bgt was elicited only by viable spores of Z.
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Plant Sci. We investigated the host-mediated interaction between the biotroph Blumeria graminis f. Both diseases are potentially severe in humid temperate climates and are controlled by fungicides and by growing wheat varieties with partial resistance.
The compatible interaction between Z. The effect on virulent Bgt was elicited only by viable spores of Z. Notably, this effect was seen before the necrotic foliar symptoms induced by Z.
Information on how different pathogens interact in host plants may allow plant breeders and others to improve the design of screening trials and selection of germplasm. Introduction Plants are exposed to many different microbes including potential pathogens.
Studies of disease on crop pathology tend to focus on individual diseases, but when environmental conditions are conducive to more than one parasite, plants must defend themselves against several species, often with different life histories. Understanding interactions between multiple pathogens on a host plant is essential for being able to control multiple diseases simultaneously in a crop.
Disease control on arable crops generally requires the combined use of pesticides and resistant varieties Torriani et al. While some groups of fungicides have broad-spectrum activity against several diseases,the scope for relying on them is diminishing because of the evolution of insensitivity in important pathogens Lucas et al.
Regarding breeding for disease resistance, a cultivar has little value to farmers if it has good resistance to one disease but high susceptibility to another disease which is also important in the same environment. Efforts to breed crop varieties resistant to multiple pathogens will be assisted by information on how important pathogens interact with each other and the mechanisms behind their interaction. This will support the design of disease screening trials and the choice of parental germplasm.
The disease outcome of infection by one pathogen may be mediated by a change in host environment brought on by infection by another pathogen. In the early mid 20th century several authors noted that cereals attacked by one pathogen predisposed them to attack by another Bensaude, ; Chester, ; Yarwood, ; Brokenshire, A reduction in disease severity has also been noted in field conditions. The non-biotrophic fungus Parastagonospora nodorum reduced the disease severity of powdery mildew Blumeria graminis although the presence of B.
In a glasshouse trial, the non-biotrophic fungal pathogen Zymoseptoria tritici reduced the incidence of Puccinia striiformis, thought to be due to competition between the two pathogens Madariaga and Scharen, Aghnoum and Niks , investigating interactions between virulent P. These previous studies demonstrate that the interactions between pathogens are not yet predictable and that there are many underlying factors in the outcome of infection.
The aim of this research was to investigate how infection of wheat with Z. Efficacy of fungicides is declining for control of this disease as the population develops insensitivity to triazole and strobulurin fungicides Fraaije et al. Currently a combination of several fungicides still gives good control of Septoria on moderately resistant wheat varieties Torriani et al. Breeding is improving the level of resistance to Septoria, but not to the extent that fungicides can be dispensed with Brown, There is also widespread insensitivity of wheat powdery mildew to broad-spectrum fungicides but it is generally well-controlled by a combination of specific anti-mildew fungicides AHDB, and partial resistance, which is generally durable Brown, The two pathogens have very different modes of infection.
This is followed by a long latent, apparently endophytic period Orton et al. During this latent period there is no detectable increase in fungal biomass Keon et al. A compatible interaction is initiated with the onset of host cell collapse and growth of the fungus in the mesophyll layer between 10 and 14 dai, after which pycnidia are formed, emerging through the stoma after at least 14 days Kema et al.
In an incompatible interaction, no increase in fungal biomass is seen Shetty et al. Bgt, by contrast, grows on the epidermis, infecting cells from appressoria formed approximately 12 h after inoculation hai. Haustoria are formed from 24 hai onwards within host cells, enabling the fungus to feed Zhang et al. Except for the haustoria, which occupy the epidermal cells, the fungus grows on the surface of the leaf throughout its lifecycle. Asexual conidiophores are produced on the surface of the leaf from 5 to 10 dai.
The hypersensitive response which forms during an incompatible interaction is a critical aspect of resistance to mildew Boyd et al. As these two pathogens cause widespread foliar diseases of wheat which often occur in the same mild, humid environments but have strongly contrasting lifestyles, their interaction is potentially of profound importance for attempts to control a broad spectrum of diseases by a combination of resistance breeding and chemical applications.
We investigated the effect of a compatible interaction between the necrotroph Z. This effect occurred several days before necrotic Septoria lesions formed, implying that signals which form during the early stages of the wheat-Z. Conversely, we tested if the maintenance of green leaf tissue during the incompatible interaction of Septoria-resistant wheat with an avirulent Z. Flame has the mildew resistance gene Pm4b and Longbow carries Pm2.
The mildew-susceptible cultivar Cerco was used as a control. Longbow, which has the Septoria resistance gene Stb15, is susceptible to Z. For plant inoculation, the second leaves of 14 days old seedlings were attached adaxial side up to Perspex sheets using double-sided tape Keon et al. The leaves were inoculated evenly with a fungal spore solution at a density of spores per mL of water using a swab stick with a cotton sterile tip Fisher Scientific, Loughborough, Leicestershire, UK; Keon et al.
Plants inoculated with Z. Control leaves were mock inoculated with water only. A method using detached leaves Arraiano et al. After 24 h in the dark the inoculated leaves were placed into the boxes and the cut ends of the leaves were covered with a layer of benzimidazole agar. Bgt isolates JIW11 and JIW48 were maintained on the wheat cultivar Cerco and were inoculated by blowing fresh spores into settling towers placed over the plant material Boyd et al. For all experiments control boxes to check for mildew colony formation and Z.
Effect of Decreasing Concentrations of Z. The dilution series started at spores per mL and inoculum was successively diluted 2. Each detached leaf box contained a leaf of Cerco and 10 leaves of Longbow encompassing the whole dilution series. The boxes were inoculated with the virulent Bgt isolate JIW48 under settling towers, 4 days after inoculation with Z.
The experiment was done in three replicates. Requirement for Living Z. The spore suspension was then inoculated onto leaves of Flame and Longbow and the leaves placed into detached leaf boxes, along with mock-inoculated leaves, before being inoculated with Bgt at 1 day after and 10 days after inoculation with the autoclaved Z. Two leaves of each treatment were included in each box and the experiment was carried out a total of three times.
Early Development of B. Leaves were inoculated with the mildew isolate JIW48, 1 or 6 days after Z. Each of three replicate experiments consisted of three independent replicate detached leaf boxes, with each box containing one leaf of each variety given each treatment.
Leaves were destructively sampled at 8 h, 24 or 32, 48, and 72 h after infection hai with Bgt Figure 1A. After the first replicate was assessed at 24 h, it was decided that 32 h would be a better timepoint to sample at as more development of the Bgt germlings had taken place.
In terms of mildew development, the 24 and 32 h time points are fairly close and in the statistical analysis each replicate was treated as a block effect. The sampled leaves were placed onto filter paper soaked in ethanol: acetic acid until they had cleared and were stored in lactoglycerol solution of lactic acid, glycerol and water until assessment by microscopy.
To visualize fungal spores, the leaves were placed on a glass slide and Aniline Blue 0. On each leaf, 30 Bgt spores were assessed for growth and development at the following stages; no germination, primary germ tube, appressorial germ tube, appressorium, balloon haustorium, digitate haustorium, or elongating secondary hyphae ESH. Only spores that were isolated, undamaged and not infecting the same cell as another spores were assessed.
Observations were made using a Nikon Microphot-SA 2 general light microscope. Haustoria were visualized under differential interference contrast DIC microscopy where necessary.
Experimental design to investigate early and late development of Blumeria graminis f. A Inoculation and data collection points to study the early development of Bgt on wheat leaves after inoculation with Z. B Inoculation and data collection points to study the late development of Bgt on wheat leaves after inoculation with a Z.
In this figure, dai refers to days after inoculation with Z. Separate statistical analyses were conducted on the data at each timepoint. The categories of Bgt development were formed into groups. At 8 h, the number of spores that had germinated with either a primary germ tube or an appressorium was studied as a proportion of the total spores counted.
At 48 and 72 h, the categories were grouped to analyze spores that had developed ESH as a proportion of the total number of infecting spores. Standard errors were calculated on a logit scale and back-transformed predicted means were calculated for the purposes of presentation. Later Development of B. Each box contained two leaves of each treatment. Two leaves of each treatment were sampled at 5, 6, 8, and 9 days after infection dai with Bgt Figure 1B.
Colony sizes were transformed to square roots for statistical analysis. This normalized the variance and made it independent of fitted values. In addition, this procedure reflects the constant radial growth rate of mildew colonies.
To check that isolate JIW48 contained the same cytochrome b gene fragment that is amplified by the primers, the fragment was cloned and sequenced. Longbow leaves were inoculated with Bgt either 1 or 6 days after inoculation with Z. The reaction mixture for qPCR contained 0.
A standard curve was produced by plotting known amounts of DNA against Cq values. Interval indicates the amount of time between inoculation with Z. DaiBg is the time that the samples were taken, either 5 or 10 days after Bgt inoculation. Trt is the treatment of Z. Standard errors were calculated using least significant differences of predicted means on a log10 scale and back-transformed for the purposes of presentation.
Results Suppression of Mildew by Preinoculation with Z. This result was consistent, regardless of whether the Bgt inoculation was carried out 2, 5, 7 or 10 dai with Z. When Flame was pre-inoculated with IPO, and subsequently inoculated with JIW48, the number of mildew colonies on pre-inoculated leaves across all replicates was similar to that on mock-inoculated leaves Figures 2A—D.
When Flame and Longbow were pre-inoculated with Z.
Echter Mehltau (Blumeria graminis f. sp. tritici, ehem. Erysiphe graminis f. sp. tritici)
Practical on Blumeria graminis f. You have segments of seedling leaves from two sets of barley isogenic lines inoculated with B. Fixation was by immersion in ethanol: glacial acetic acid v:v for 24h by which time all chlorophyll had been removed. Segments were then washed in water for 5 min. The fungus was stained for 2h in 0. Tissues then stored in lactoglycerol and mounted in same. Alg-R has the dominant allele Mla-1 which conditions a rapid hypersensitive reaction to attack by avirulent races of B.
Systematics[ edit ] Previously B. Thus since , the species graminis was moved into the new taxa Blumeria of which is the only species. Blumeria differs from Erysiphe in its digitate haustoria and in details of the conidial wall. As well Blumeria is considered to be phylogenetically distinct from Erisiphe as it is a plant pathogen that hosts solely on the true grasses of Poaceae. Eight special forms or formae speciales ff.