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1.
Flávia E. de Mello Valéria S. Lopes-Caitar Sheila A. Xavier-Valencio Helen P. da Silva Sören Franzenburg Andreas Mehl Joseph-Alexander Verreet Maria I. Balbi-Peña Francismar C. Marcelino-Guimaraes Cláudia V. Godoy 《Plant pathology》2022,71(2):373-385
Fungicide sprays on soybean in Brazil have contributed to the selection of less sensitive isolates of Corynespora cassiicola. We collected 59 isolates of C. cassiicola from three Brazilian states and two isolates from Paraguay. We investigated their EC50 to quinone outside inhibitors (QoI) and methyl benzimidazole carbamate (MBC), any cross-resistance to compounds within QoI and MBC groups, and characterized the polymorphisms in their cytb and β-tubulin genes. Local associations of polymorphisms identified in each gene were statistically correlated with assays results. In total, 79% and 74% of the isolates were classified as resistant to QoI and MBC fungicides, respectively. There was positive cross-resistance to active ingredients within QoI and MBC groups. For QoI, all isolates presented heteroplasmy in G143A of cytb gene; the mutations F129L and G137R were not found. For MBC, 63% of isolates possessed E198A and 21% possessed F200Y mutations, associated with reduced control by MBC fungicides. Heteroplasmy was identified in two and one isolates from Brazil with E198A and F200Y mutations, respectively. The resistance factor for isolates with E198A (10.9) was statistically similar to the isolate with F200Y (8.8) mutation. Genic association analysis of the in vitro assays using discriminatory doses proved them to be accurate. Reduced sensitivity of C. cassiicola to QoI and MBC was also identified in isolates from Paraguay and resistance to QoI and MBC was widely present in C. cassiicola isolates from the main soybean-producing states in Brazil. Thus, integrated management measures should be adopted to manage soybean target spot in these countries. 相似文献
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Omar M. R. Abd-Elsalam K. A. Aly A. A. El-Samawaty A. M. A. Verreet J. -A. 《植物病害和植物保护杂志》2007,114(5):196-204
Journal of Plant Diseases and Protection - Pathogenicity of 21 isolates of Macrophomina phaseolina was tested on three cotton cultivars under greenhouse conditions. Analysis of variance (ANOVA)... 相似文献
3.
Marco?BeyerEmail author Joseph-Alexander?Verreet 《European journal of plant pathology / European Foundation for Plant Pathology》2005,111(4):381-389
The effects of age of ascospores (0–18 days after discharge), photon flux density (0–494 mol m–2 s–1 PAR), temperature (4–30 °C), frost (–15 °C for 30 min), relative humidity (RH; 0–100%), pH (2.5–6.5) and dryness (0 and 53% RH for up to 40 min) on the germination of the ascospores of the mycotoxin-producing fungus Gibberella zeae (anamorph Fusarium graminearum) were studied. Freshly discharged ascospores germinated within 4 h at 20 °C and 100% RH. The rate of germination and the percentage of viable ascospores decreased over time after the spores were discharged from perithecia. The time course of ascospore germination was not significantly affected by photon flux density. The period of time required to obtain 50% germinated ascospores at 100% RH was 26.90 h at 4 °C, 10.40 h at 14 °C, 3.44 h at 20 °C and 3.31 h at 30 °C. There was no significant effect of frost on the percentage of viable ascospores. A small percentage (6.6 ± 3.8%) of the ascospores germinated at 53% RH. At RH 84% and 20 °C almost 100% of the freshly discharged ascospores germinated. The time course of ascospore germination was affected by pH. The maximum rate of ascospore germination was estimated to be at pH 3.76. Ascospores lost their ability to germinate following exposure to 0% RH almost instantaneously. No germinating spores were detected after an incubation period of 1 min at 0% RH. Incubating the ascospores at 53% RH decreased the percentage of viable spores from 93 to 6% within 10 min. The data demonstrate that age of spores, relative humidity, temperature and pH, but not photon flux density, are key factors in germination of G. zeae ascospores. 相似文献
4.
ABSTRACT Severe Cercospora leaf spots epidemics in sugar beet during the late 1980s and early 1990s in southern Germany prompted us to initiate investigations on the epidemiology of the causal agent, Cercospora beticola. The data set involved 69 field trials (1993 to 2003) focusing on factors affecting the epidemic onset of this disease. Observations were made at weekly intervals, recording the calendar week when canopy closure occurred (growth stage according to BBCH scale = 39) and symptom development by assessing the percentage of infected leaf area on a single-leaf basis (n = 40 plants). These monitoring trials revealed that epidemic onset varied between early July and mid-September. Hence, the target was to identify the reasons for this variation in order to deduct the most suitable approach for predicting epidemic onset. Differences in cultivar resistance explained part of epidemic onset variability, as did different timings of canopy closure, presumably due to associated microclimate changes. Moreover, meteorological variables were considered as potential reasons for variation in epidemic onset. The weather-dependent infection probability was assessed by daily infection values (DIV) in the range from 0 to 1 using hourly weather data. For calculating DIVs, the temperature effect was quantified by the proportions of the latent period (LP) relative to the optimum at 20 to 25 degrees C, established by artificial inoculation of sugar beet plants in growth cabinets. Artificial infection experiments further established that air relative humidity (RH) >95% or leaf wetness was required for infection and subsequent lesion development. Under field conditions, the probability of leaf wetness was 75% at RH >90%. Therefore, DIVs were set to 0 for RH =90% in the absence of precipitation (moisture index I). Alternatively, the effect of moisture was modeled with a sigmoidal function describing the occurrence of leaf wetness in dependence of RH in the field (moisture index II). Using this approach, DIV values were cumulated (c-DIV) for each of the 69 trials beginning either at fixed starting dates (1 May, 16 May, or 1 June) or the dates of canopy closure. Accumulation of DIV ended at the time of epidemic onset. The two different moisture index definitions had no significant influence on c-DIV; whereas, for starting time of summation of DIV, the date of canopy closure was more suitable. Values of c-DIV ranged from 7 to 19 in highly susceptible cultivars and 12 to 25 in cultivars with lower susceptibility. Given this variation, c-DIV values were insufficient to explain differences in the date of epidemic onset and thus were not considered suitable for making accurate and precise management decisions. However, a negative prognosis assessing the most likely periods of disease absence was possible by determining the minimum c-DIV as a threshold. This threshold was 7 c-DIV for highly susceptible cultivars and 12 c-DIV for cultivars with low susceptibility. Crop monitoring is recommended as soon as these threshold values are exceeded so that the exact epidemic onset time can be observed. 相似文献
5.
Journal of Plant Diseases and Protection - The effects of different cultivation systems on disease incidence and severity in oilseed rape were investigated on two sites in Schleswig-Holstein in the... 相似文献
6.
Abd-Elsalam K. A. Schnieder F. Asran-Amal A. Khalil M. S. Verreet J. A. 《植物病害和植物保护杂志》2003,110(5):409-418
Journal of Plant Diseases and Protection - Fusarium semitectum, which occurs frequently among the fungal microflora associated with seedling disease of cotton, was examined using traditional... 相似文献
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Journal of Plant Diseases and Protection - Grains of the three differentially Fusarium-susceptible winter wheat cultivars “Ritmo” (highly susceptible), “Inspiration”... 相似文献
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Journal of Plant Diseases and Protection - 相似文献
9.
Journal of Plant Diseases and Protection - The geographic distribution and DNA-disease severity of the anastomosis groups (AG) 1 IA, AG 1 IB and AG 2-2 IIIB within the teleomorph Thanatephorus... 相似文献
10.
Journal of Plant Diseases and Protection - Deoxynivalenol (DON) is a mycotoxin produced by fungi of the genus Fusarium. Maximum tolerable DON concentrations for grain and selected wheat products... 相似文献