TY  - JOUR
AB  - The AlphaproteobacteriumRhizobium radiobacter(syn.Agrobacterium tumefaciens, "A. fa brum") can live in close association with the sebacinoid fungusSerendipita(syn.Piriformospora)indicathat forms a mutualistic Sebacinalean symbiosis with a wide range of host plants. The endobacterial strainR. radiobacterF4 (RrF4), which was originally isolated from the fungus, has plant growth promotion and resistance-inducing activities resembling the beneficial activities known from the endobacteria-containingS. indica. The mechanism by which free endobacterial cells influence growth and disease resistance of colonized host plants is not fully understood. Here, we show thatRrF4 produces a spectrum of quorum sensing-mediatingN-acyl-homoserine lactones (AHLs) with acyl chains of C8, C10, and C12 as well as hydroxyl- or oxo-substitutions at the C3 position. In addition, and in line with previous findings showing that AHLs increase plant biomass and induce systemic resistance, the AHL-depleted lactonase-overexpressing transconjugantRrF4NM13 was partially compromised in promoting growth and inducing resistance against bacterial pathogens in bothArabidopsis thalianaand wheat (Triticum aestivum). Scanning and transmission electron microscopy proved thatRrF4NM13, in contrast toRrF4, does not form cellulose-like fiber scaffolds for efficient root surface attachment. Moreover,RrF4NM13 does not penetrate into the intercellular space of the cortical tissue, which in contrast is strongly colonized byRrF4. We discuss the possibility that AHLs contribute to the outcome of the Sebacinalean symbiosis.
AU  - Alabid, I.*
AU  - Hardt, M.*
AU  - Imani, J.*
AU  - Hartmann, A.
AU  - Rothballer, M.
AU  - Li, D.
AU  - Uhl, J.
AU  - Schmitt-Kopplin, P.
AU  - Glaeser, S.*
AU  - Kogel, K.H.*
C1  - 59849
C2  - 49070
CY  - Tiergartenstrasse 17, D-69121 Heidelberg, Germany
SP  - 769–781
TI  - The N-acyl homoserine-lactone depleted Rhizobium radiobacter mutant RrF4NM13 shows reduced growth-promoting and resistance-inducing activities in mono- and dicotyledonous plants.
JO  - J. Plant Dis. Prot.
VL  - 127
PB  - Springer Heidelberg
PY  - 2020
SN  - 0340-8159
ER  - 

TY  - JOUR
AB  - One of the problems encountered when studying the population genetics of fungal plant pathogens is defining what constitutes a "population". Potato early blight is a major disease of potatoes and other species of the Solanaceae. The causal agent is the ascomycete Altemaria solani, which infects leaves and stems of potato plants leading to premature defoliation. In this study, spatial genetic diversity within A. solani populations from potato leaves were investigated using RAPD markers in order to reveal the degree of homo- or heterogeneity. Analysis of RAPD profiles revealed distinct genetic diversity among isolates originating from the same field. In addition, pronounced genetic variability was found for isolates from different years. These results indicate a surprising genetic heterogeneity within the population of A. solani, which must be kept in mind when designing protective measures for agriculture.
AU  - Leiminger, J.*
AU  - Auinger, H.-J.*
AU  - Wenig, M.
AU  - Bahnweg, G.
AU  - Hausladen, H.*
C1  - 26835
C2  - 32410
SP  - 164-172
TI  - Genetic variability among Alternaria solani isolates from potatoes in Southern Germany based on PAPD-profiles.
JO  - J. Plant Dis. Prot.
VL  - 120
IS  - 4
PB  - Ulmer
PY  - 2013
SN  - 0340-8159
ER  - 

TY  - JOUR
AB  - A complete growth season with the physical climate and ozone pollution from 1 April to 31 July as recorded at a field site in Northern Germany, averaged over several years, was simulated in climate chambers and combined either with a current (370-400 mu l l(-1)) or enriched (620-650 mu l l(-1)) CO2 atmosphere. Wheat, grown from seedling emergence to maturity under the different physico-chemical climates, was inoculated with leaf rust (Puccinia recondita f. sp. tritici) at tillering stage and a rust epidemic was induced by repeated re-inoculations with the newly Formed inoculum. Ozone significantly reduced disease severity, uredospore production and increased the latent period of leaf rust on young planes, consequently inhibiting the epidemic spread on upper leaves of mature plants. Inhibiting effects of ozone on leaf rust development were not reflected by the early infection stages such as spore germination, germ tube growth, formation of infection hyphae, haustorial mother cells and haustoria, which remained largely unaffected by the ozone treatments. However, ozone induced a significantly higher extent of hypersensitive responses of the infected leaf tissue. Additionally, plants exposed to elevated ozone turned senescent much earlier than plants without this stress which prematurely degraded the growth conditions for the fungal pathogen. Enrichment with CO2 increased the rotal carbohydrate content in leaves but this had only minor effects on the disease. Thus, elevated CO2 only poorly compensated for the disease-inhibiting effects of ozone. The compensation of ozone effects on wheat leaf rust by elevated CO2 is much smaller than known compensatory effects of both gases on plans productivity.
AU  - von Tiedemann, A.*
AU  - Firsching, K.H.
C1  - 23452
C2  - 31161
SP  - 555-566
TI  - Combined whole-season effects of elevated ozone and carbon dioxide concentrations on a simulated wheat leaf rust (Puccinia recondita f. sp. tritici) epidemic.
JO  - J. Plant Dis. Prot.
VL  - 105
IS  - 6
PB  - Ulmer
PY  - 1998
SN  - 0340-8159
ER  - 

TY  - JOUR
AB  - In Feldversuchen über drei Vegetationsperioden wurde eine neue Methode zur Unkrautbekämpfung in foliengemulchtem Zuckermais erprobt. Das Verfahren basiert auf der homogenen Inkorporation von Atrazin in foliengeeignete Kunststoffe, insbesondere Ethylen-vinylacetat-Copolymere (EVA). Die diffusionskontrollierte Freisetzung des Wirkstoffes erfolgte über einen Zeitraum von 2-4 Wochen. Bei den höher konzentrierten Folienvarianten (0,2 % - 1,0 % Atrazin) waren jedoch bereits zu Versuchsbeginn erhebliche Anteile des Wirkstoffinventars an die Polymeroberfläche migriert, wodurch die Abgabe des Herbizids bei niederschlagsreicher Witterung beschleunigt wurde. Ein Herbizidgehalt der Folien von nominal 0,025 % ≙ 0,18 kg/ha erwies sich gegen Unkräuter und Indikatorpflanzen schon als so wirksam, daß eine weitere Reduzierung der Konzentration möglich erscheint. Die konventionelle Applikation von Atrazin zeigte bei jeweils vergleichbaren Aufwandmengen eine ähnliche starke herbizide Wirkung. Im Versuchsjahr 1985 deutete sich allerdings eine höhere Effektivität der Folienapplikation an. Die Erträge an Maiskolben waren in den einzelnen Versuchsperioden unabhängig von der Art der Herbizidbehandlung sehr einheitlich, jedoch stets signifikant höher als in den ungemulchten Kontrollen. Atrazinrückstände wurden in den Maisproben nicht, jedoch in Bodenproben in Abhängigkeit von den Aufwändmengen im Bereich von 5 μg/kg bis 175 μg/kg gefunden. Die Rückstandsbildung schien bei Applikation der herbiziden Folien im allgemeinen niedriger zu sein.
AU  - Pfister, G.
AU  - Bahadir, M.
C1  - 17295
C2  - 10297
SP  - 317-329
TI  - Mulchfolien mit inkorporiertem Atrazin zur Unkrautbekämpfung in Zuckermais.
JO  - J. Plant Dis. Prot.
VL  - 96
IS  - 3
PY  - 1988
SN  - 0340-8159
ER  -