Detection of the 3-phosphoglycerate kinase protein of Glomus mosseae

 The Glomus mosseae 3-phosphoglycerate kinase (PGK) gene encodes a polypeptide of 416 amino acids. A synthetic peptide was designed to the C-terminus of the polypeptide for the production of a polyclonal antibody. The antibody was tested against the synthetic peptide in an immuno-dot blot and was then used to investigate the asymbiotic and symbiotic accumulation of the PGK protein. Western blot analysis revealed that a polypeptide of approximately 45 kDa accumulated in G. mosseae-colonised tomato roots; this is similar to the theoretical molecular weight of 44.764 kDa. The protein was not detected in non-mycorrhizal roots. Quantitative immuno-dot blotting revealed that the polypeptide accumulated in germinating spores and hyphae of G. mosseae and also in tomato roots colonised by G. mosseae. The amount detected in the mycorrhizal root system was significantly higher than that found in germinating sporocarps. The variation in the levels of glycolytic activity in the symbiotic and asymbiotic developmental stages of G. mosseae is discussed. Accepted: 20 April 2000     

Surface-sterilization of Glomus mosseae sporocarps for studying endomycorrhization in vitro

 The effects of sterilization time, sterilizing agents (ethanol, Chloramine T, calcium hypochlorite) and antibiotics (streptomycin and gentamycin) on Glomus mosseae (BEG 12) sporocarp germination and contamination were evaluated. Incubation for 10 s in 96 % ethanol, followed by 10 min in a solution of 2% Chloramine T, 0.02% streptomycin, 0.01% gentamycin and Tween 20, and then 6 min in 6% calcium hypochlorite greatly reduced fungal and bacterial contamination from sporocarps and caused little change in germination rate in water agar medium. Accepted: 4 March 1999     

A high-resolution genetic map and a diagnostic RFLP marker for the Mlg resistance locus to powdery mildew in barley

The semi-dominantly acting Mlg resistance locus in barley confers race-specific resistance to the obligate biotrophic fungus Erysiphe graminis f.sp. hordei. A high-resolution genetic map was constructed at Mlg based on a cross between the near-isogenic barley lines Pallas BC₅ Mlg and Pallas mlg. A total of 2000 F₂ progeny were inspected by cleaved amplified polymorphic sequence (CAPS) analysis, defining a 4.47 cM interval encompassing the resistance locus. Pathogen challenge of the segregants with multiple powdery mildew isolates uncovered a novel resistance specificity in Pallas BC₅ Mlg. Probes from within 4.0 cM of Mlg were mapped in rice, revealing orthologues on five different rice chromosomes and suggesting multiple breaks of chromosomal collinearity in this region between the two grass species. The most tightly Mlg-linked RFLP marker, MWG032, was shown to reliably detect the presence of the resistance allele in a collection of 30 European barley cultivars. Received: 23 March 2000 / Accepted: 20 April 2000     

RFLP markers to identify the alleles on the Mla locus conferring powdery mildew resistance in barley

Summary To identify the mildew resistance locus Mla in barley with molecular markers, closely linked genomic RFLP clones were selected with the help of near-isogenic lines having the Pallas and Siri background. Out of 22 polymorphic clones 3 were located around the Mla locus on chromosome 5 with a distance of 5.1 + 2.9 cM (MWG 1H068), 4.2±1.7 cM (MWG 1H060) and 0.7 ± 0.7 cM (MWG 1H036), respectively. The polymorphic clone MWG 1H036 displayed the same RFLP pattern in both Pallas and Siri near-isogenic lines and in different varieties digested with six restriction enzymes possessing the same mildew resistance gene. The alleles of the Mla locus were grouped in 11 classes according to their specific RFLP patterns; 3 of these groups contain the majority of Mla alleles already used in barley breeding programs in Europe.     

Influence of soil impoverishment on the interaction between Glomus mosseae and saprobe fungi

 The effect of the saprobe fungi Wardomyces inflatus (Marchal) Hennebert, Paecilomyces farinosus (Holm & Gray) A. H. S. Brown & G. Sm., Gliocladium roseum Bain., Trichoderma pseudokoningii Rifai and T. harzianum Rifai, isolated from sporocarps of Glomus mosseae, on arbuscular mycorrhizal (AM) colonisation and plant dry matter of soybean was studied in 2/3 and 1/5 diluted soils in a greenhouse trial. Soil dilution to 1/5 had no effect on shoot dry matter of soybean but decreased AM colonisation and root dry weight of plants. CFU of saprobe fungi, except T. harzianum, were higher in 1/5 than in 2/3 diluted soils. W. inflatus and Gliocladium roseum decreased the shoot dry weight of soybean plant when inoculated together with Glomus mosseae. The saprobe fungi P. farinosus and T. pseudokoningii increased the shoot dry weights of plants grown in 1/5 diluted soil. The shoot dry weight and AM colonisation in 1/5 diluted soil were also increased when T. harzianum was inoculated together with Glomus mosseae. Thus, saprobe fungi increased AM colonisation of soybean plants by indigenous endophytes. The AM colonisation of plants at both soil dilutions was increased by Glomus mosseae. The highest level of AM colonisation was observed when P. farinosus and T. pseudokoningii were inoculated together Glomus mosseae. The dilution of soils influenced the interaction between inoculated microorganisms and their effect on plant growth. Accepted: 7 June 1999     

Root colonization by the arbuscular mycorrhizal fungus Glomus mosseae and enhanced phosphorous levels in cucumber do not affect host acceptance and development of Frankliniella occidentalis

Abstract

We tested the effect of root colonization of cucumber (Cucumis sativus L.) by the arbuscular mycorrhizal fungus (AMF) Glomus mosseae on different parameters of a plant-thrips (Frankliniella occidentalis Pergande) interaction. In leaf disc bioassays, the feeding activity, the oviposition rate, the settling preference of adult females and the developmental time (first instar larva to adult) on leaves of mycorrhizal and non-mycorrhizal plants were studied. To distinguish between a nutritional effect through an improved phosphorous (P) status of the mycorrhizal plant and other effects caused by mycorrhization, non-mycorrhizal plants watered with a nutrient solution with (+P) or without P (?P) were included in the study. Mycorrhization did not affect any of the parameters on host acceptance tested, whereas on plants with a higher P-level the duration of the non-feeding stages (pronymphae, nymphae) of F. occidentalis was shortened, but all other developmental parameters were similar as in the control and the mycorrhizal plants. Our data indicate that the polyphagous thrips F. occidentalis is neither affected by mycorrhization of cucumber plants nor by enhanced P-levels.     

Bacterial associations with the mycorrhizosphere and hyphosphere of the arbuscular mycorrhizal fungus Glomus mosseae

Roots and mycorrhizal fungi may not associate with soil bacteria randomly, but rather in a hierarchical structure of mutual preferences. Elucidation of such structures would facilitate the management of the soil biota to enhance the stability of the plant-soil system. We conducted an experiment utilizing two isolates of soil bacteria to determine their persistence in distinct mycorrhizal regions of the root zone, and their effects on general rhizosphere populations of fluorescent pseudomonads (FP). Split-root sorghum (Sorghum bicolor L.) plants were grown in four-compartment containers, constructed so that the soils in individual compartments held either (1) roots colonized by the arbuscular-mycorrhizal (AM) fungus Glomus mosseae (M), (2) nonAM roots only (R), (3) hyphae of G. mosseae (H), or (4) no mycorrhizal structures (S). The soils were inoculated (10⁷ cells g^-1 dry soil) with antibiotic-resistant (rifampicin, rif; streptomycin, sm) strains of the soil bacteria, Alcaligenes eutrophus (rif^r50) or Arthrobacter globiformis (sm^r250), or were left uninoculated as control. A. eutrophus had been isolated from a specific source (hyphosphere soil of G. mosseae), and A. globiformis from mycorrhizosphere soils of two AM fungi. After 10 wk of growth, the presence of A. eutrophus was barely detectable (<10 cfu g^-1 dry soil) in nonAM (R and S) soils, but persisted well (10⁴ cfu g^-1 dry soil) in AM (H and M) soils. Numbers of A. globiformis were more evenly distributed between all soils, but were highest in the presence of AM roots (M soil). There were varied bacterial effects on root and AM-hyphal development: A. eutrophus decreased hyphal length in H soil, while A. globiformis stimulated root length in M soil. The two bacterial inoculants did not affect numbers of FP in H, R, and M soils, but the AM status of the soils did: the numbers of FP increased in the order M>R>H>S. There was a positive correlation of FP numbers with both bacterial inoculants in M and H soils. Numbers of FP changed with root or hyphal lengths, an effect that was related to changes in the numbers of the inoculated bacteria. The results indicate that the hyphosphere-specific A. eutrophus depended on the presence of G. mosseae, but that the nonspecific A. globiformis did not. The mycorrhizal status of soils may selectively influence persistence of bacterial inoculants as well as affecting the numbers of other native bacteria.     

Sources of powdery mildew resistance in barley landraces from morocco

A total of forty eight accessions of barley landraces from Morocco were screened for resistance to powdery mildew. Twenty two (46%) of tested landraces showed resistance reactions and thirty four single plant lines were selected. Eleven of these lines were tested in seedling stage with seventeen and another twenty three lines with twenty three isolates of powdery mildew respectively. The isolates were chosen according to the virulence spectra observed on the ‘Pallas’ isolines differential set. Line 229–2–2 was identified with resistance to all prevalent in Europe powdery mildew virulence genes. Lines 230–1–1, 248–1–3 showed susceptible reaction for only one and lines 221–3–2, 227–1–1, 244–3–4 for only two isolates respectively. Three different resistance alleles (Mlat, Mla6, and MLA14) were postulated to be present in tested lines alone or in combination. In thirty (88%) tested lines it was impossible to determine which specific gene or genes for resistance were present. Most probably these lines possessed alleles not represented in the ‘Pallas’ isolines differential set. The distribution of reaction type indicated that about 71% of all reaction types observed were classified as powdery mildew resistance (scores 0, 1 and 2). Majority (79%) of resistance reaction types observed in tested lines was intermediate resistance reaction type two and twenty three lines (68%) showed this reaction for inoculation with more than 50% isolates used. The use of new effective sources of resistance from Moroccan barley landraces for diversification of resistance genes for powdery mildew in barley cultivars was discussed.     

Molecular mapping of the wheat powdery mildew resistance gene Pm24 and marker validation for molecular breeding

Molecular markers were identified in common wheat for the Pm24 locus conferring resistance to different isolates of the powdery mildew pathogen, Erysiphe graminis DM f. sp. tritici (Em. Marchal). Bulked segregant analysis was used to identify amplified fragment length polymorphism (AFLP) markers and microsatellite markers linked to the gene Pm24 in an F₂ progeny from the cross Chinese Spring (susceptible)× Chiyacao (resistant). Two AFLP markers XACA/CTA-407 and XACA/CCG-420, and three microsatellite markers Xgwm106, Xgwm337 and Xgwm458, were mapped in coupling phase to the Pm24 locus. The AFLP marker locus XACA/CTA-407 co-segregated with the Pm24 gene, and XACA/CCG-420 mapped 4.5 cM from this gene. Another AFLP marker locus XAAT/CCA-346 co- segregated in repulsion phase with the Pm24 locus. Pm24 was mapped close to the centromere on the short arm of chromosome 1D, contrary to the previously reported location on chromosome 6D. Pm24 segregated independently of gene Pm22, also located on chromosome 1D. An allele of microsatellite locus Xgwm337 located 2.4±1.2 cM from Pm24 was shown to be diagnostic and therefore potentially useful for pyramiding two or more genes for powdery mildew resistance in a single genotype. Received: 25 August 1999 / Accepted: 16 December 1999     

Chromosomal location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L. em Thell.). 5. Alleles at the Pm1 locus

 The chromosomal location and genetic characterization of powdery mildew resistance genes were determined in the common wheat lines MocZlatka, Weihenstephan Stamm M1N and in a resistant line of Triticum aestivum ssp. spelta var. duhamelianum. Monosomic analyses revealed that one major dominant gene is located on chromosome 7A in each of the lines tested. Allelism tests with Pm1 in the backcross-derived line Axminster/8^*Cc on 7A indicated that the resistance genes are alleles at the Pm1 locus. These alleles are now designated Pm1a in line Axminster/8^*Cc, Pm1b in MocZlatka, Pm1c in Weihenstephan Stamm M1N, and Pm1d in T. spelta var. duhamelianum, respectively. Received: 10 November 1997 / Accepted: 29 January 1998     

Field resistance of spring barley cultivars to powdery mildew in Lithuania

During vegetative period 2004–2005 powdery mildew (Erysiphe graminis DC. f. sp. hordei Em. Marchal) field resistance of spring barley cultivars was investigated at the Lithuanian Institute of Agriculture. The spring barley genotypes tested were Lithuania-registered cultivars, cultivars from genetic resources collection, and the new cultivars used for initial breeding. In total, 23 resistance genes were present in the 84 cultivars studied. Among mono-genes only mlo and 1-B-53 showed very high resistance. Slight powdery mildew necroses (up to 3 scores) formed on cultivars possessing these genes. The maximal powdery mildew (PM) severity reached a score of 8.5 and the area under disease progress curve (AUDPC) a value of 1216.8. The cultivars ‘Primus’, ‘Astoria’, ‘Power’, ‘Harrington’ and ‘Scarlett’ were the most resistant among the non mlo cultivars. Severity of PM on ‘Primus’ reached a score of 3.5 (3.0 of PM necrosis) in average, the other cultivars were diseased from 4.5 (3.0) to 5.0 (2.0). The AUDPC values for these cultivars except ‘Scarlett’ were the lowest (85.0–145.3) among the other cultivars. The highest contrast in development of the other leaf diseases was between highly resistant and susceptible to PM cultivar groups. The fast development of PM depressed development of the other diseases 4.7 times.     

Effect of enhanced atmospheric CO2 on mycorrhizal colonization by Glomus mosseae in Plantago lanceolata and Trifolium repens

Plantago lanceolata L. and Trifolium repens L. were grown for 16 wk in ambient (360 μmol mol⁻¹) and elevated (610 μmol mol⁻¹) atmospheric CO₂. Plants were inoculated with the arbuscular mycorrhizal (AM) fungus Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe and given a phosphorus supply in the form of bonemeal, which would not be immediately available to the plants. Seven sequential harvests were taken to determine whether the effect of elevated CO₂ on mycorrhizal colonization was independent of the effect of CO₂ on plant growth. Plant growth analysis showed that both species grew faster in elevated CO₂ and that P. lanceolata had increased carbon allocation towards the roots. Elevated CO₂ did not affect the percentage of root length colonized (RLC); although total colonized root length was greater, when plant size was taken into account this effect disappeared. This finding was also true for root length colonized by arbuscules. No CO₂ effect was found on hyphal density (colonization intensity) in roots. The P content of plants was increased at elevated CO₂, although both shoot and root tissue P concentration were unchanged. This was again as a result of bigger plants at elevated CO₂. Phosphorus inflow was unaffected by CO₂ concentrations. It is concluded that there is no direct permanent effect of elevated CO₂ on mycorrhizal functioning, as internal mycorrhizal development and the mycorrhizal P uptake mechanism are unaffected. The importance of sequential harvests in experiments is discussed. The direction for future research is highlighted, especially in relation to C storage in the soil.     

Interactions between Pseudomonas fluorescens biocontrol agents and Glomus mosseae, an arbuscular mycorrhizal fungus, within the rhizosphere

Interactions between Pseudomonas fluorescens biocontrol agents and Glomus mosseae , an arbuscular mycorrhizal fungus, were studied. The biocontrol agents included the genetically modified strains CHA96 and CHA0 pME3424 which produced enhanced levels of antifungal compounds. Tomato ( Lycopersicum esculentum ) and leek ( Allium porrum ) host plants were grown in sterile Terra-Green (calcined attapulgite clay) with limited nutrients. Mycorrhizal activity was indicated by shoot dry weight and phosphorus content. In all experiments, plants grown in the presence of G. mosseae had a significantly higher shoot dry weight than those grown in the absence of G. mosseae . Colonisation and activity of G. mosseae was unaltered in the presence of P. fluorescens isolates and presence of G. mosseae increased the population of P. fluorescens in the rhizosphere.     

Chromosomal location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L. em. Thell.) 4. Gene Pm 24 in Chinese landrace Chiyacao

 Chinese wheat landrace Chiyacao exhibited a response pattern different from that of the cultivars/lines possessing documented Pm genes after inoculation with 106 isolates of Erysiphe graminis f. sp. tritici. To characterize this resistance and to determine the chromosomal location of the gene or genes present, we crossed the landrace to susceptible cultivar ‘Chinese Spring’ and also to a set of 21 ‘Chinese Spring’ monosomic lines. Monosomic F₁ plants were allowed to self-pollinate and to produce F₂ seeds. Seedlings of F₂ plants and their parents were inoculated with isolates nos. 5 and 12 of Erysiphe graminis f. sp. tritici. The results revealed that one major dominant gene is located on chromosome 6D of Chinese common wheat landrace Chiyacao. The new gene is designated Pm 24. Received: 12 May 1997 / Accepted: 23 May 1997     

Chromosomal location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L. em Thell.) 6. Alleles at the Pm5 locus

Genetic characterization of powdery mildew resistance genes were conducted in common wheat cultivars Hope and Selpek possessing resistance gene Pm5, cvs. Ibis and Kormoran expressing resistance gene Mli, a backcross-derived line IGV 1–455 and a Triticum sphaerococcum var. rotundatum Perc. line Kolandi. Monosomic analyses revealed that one major recessive gene is located on chromosome 7B in the lines IGV 1–455 and Kolandi. Allelism tests of the F₂ and F₃ populations involving the tested resistant lines crossed with either cv. Hope or Selpek indicated that their resistance genes are alleles at the Pm5 locus. The alleles are now designated Pm5a in Hope and Selpek, Pm5b in Ibis and Kormoran, Pm5c in T. sphaerococcum var. rotundatum line Kolandi, and Pm5d in backcross-derived line IGV 1–455, respectively. Received: 5 November 1999 / Accepted: 14 April 2000     

亚蔬中心绿豆品种(系)抗白粉病评价

采用苗期人工接种鉴定法,在大棚种植条件下对12个亚蔬中心(AVRDC)绿豆品种白粉病抗性进行了鉴定评价。结果显示,VC1560C、V4785和VC2768A三个品种高抗(HR)白粉病,VC6173-14、V1132为中抗(MR)白粉病品种。其它品种对白粉病表现高度感病。在田间种植条件下对亚蔬中心16个抗豆象回交9代品系(BC9)进行了成株期白粉病抗性鉴定。与对照感病品种 VC1973、VC1178A 相比,VC6459-3-6-37和 VC6458-6-3-16对白粉病具有一定抗性,但白粉病感染程度仍很严重,其它14个 BC9品系均对白粉病表现高度感病。     

Resistance to oat powdery mildew in Britain and Europe: a review

The evolution of virulence in UK oat powdery mildew (Blumeria graminis f.sp. avenae) populations is presented along with comparative information on the deployment of resistant cultivars. Virulence frequencies have followed classical gene‐for‐gene principles, and there are no effective resistance genes currently deployed in cultivars grown in the UK. The incidence of powdery mildew in continental Europe and pathogen variation is reviewed as well as other strategies for the control of this disease. New resistant sources have been identified and are being used in breeding programmes throughout Europe.     

Expression studies of plant genes differentially expressed in leaf and root tissues of tomato colonised by the arbuscular mycorrhizal fungus Glomus mosseae

Arbuscular mycorrhizal (AM) fungi are a multifaceted group of mutualistic symbionts that are common to terrestrial ecosystems. The interaction between AM fungi and plant roots is of environmental and agronomic importance. Understanding the molecular changes within the host plant upon AM fungal colonisation is a pre-requisite to a greater understanding of the mechanisms underlying the interaction. Differential mRNA display was conducted on leaf tissue of tomato plants colonised and non-colonised by the AM fungus Glomus mosseae and five putative differentially regulated cDNAs were identified. All cDNAs isolated shared high sequence similarity to known plant genes. Differential screening was initially used to establish whether the cDNAs were differentially expressed. Semi-quantitative RT-PCR was used to establish gene expression patterns for all five clones within leaf and root tissue of mycorrhizal and non-mycorrhizal colonised tomato plants. Differential regulation was observed for all five cDNAs. Down-regulation within the leaf tissue of mycorrhizal plants was observed for 4 out of the 5 cDNAs with an up-regulation observed only for one. Tissue specific regulation was observed for several cDNAs, with down-regulation observed in mycorrhizal leaf tissue and up-regulation observed within mycorrhizal root tissue as compared to non-mycorrhizal tissue.