Key Laboratory of Integrated Crop Pests Management of Shandong Province

Qingdao, China

Key Laboratory of Integrated Crop Pests Management of Shandong Province

Qingdao, China
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Sun S.,Key Laboratory of Integrated Crop Pests Management of Shandong Province | Sun S.,Qingdao Agricultural University | Lian S.,Key Laboratory of Integrated Crop Pests Management of Shandong Province | Lian S.,Qingdao Agricultural University | And 10 more authors.
Plant Disease | Year: 2017

Cucumber downy mildew, caused by Pseudoperonospora cubensis, is a worldwide disease that causes severe damage to cucumber production. The effects of temperature and moisture on sporulation and infection by P. cubensis were investigated by inoculating cucumber (‘85F12’) cotyledons with sporangia and examining the sporangia produced on the inoculated cotyledons under artificially controlled environments. The result showed that the temperature required for sporangium infection by P. cubensis and sporulation of the downy mildew lesions occurred at 5 to 30°C. The optimal temperature estimated by the fitted model was 18.8°C for sporangium infection and 16.2°C for downy mildew lesion sporulation. The pathogen formed plenty of sporangia when disease cotyledons were wetted or in the environment with relative humidity = 100%. The downy mildew lesions produced only a few sporangia when placed in the environment with relative humidity = 90%. The inoculated cotyledons, which incubated for 5 days at about 20°C in a dry greenhouse, began to form sporangia 4 h after being wetted when incubated in darkness. The quantity of sporangia produced on the downy mildew lesions increased with extension of incubating period (within 12 h), and the relationship between produced sporangia and the incubation period at 15, 20, and 25°C can be described by three exponential models. The observed minimum wetness durations (MWD) required for sporangia to complete the infection process and cause downy mildew were 12, 4, 2.5, 1, 1, and 6 h for 5, 10, 15, 20, 25, and 30°C, respectively. The effect of temperature and wetness duration on infection by sporangia of P. cubensis can be described by the modified Weibull model. The shortest MWD was 0.45 h, about 27 min, estimated by model. The experimental data and models will be helpful in the development of forecasting models and effective control systems for cucumber downy mildew. © 2017 The American Phytopathological Society.


Zhou S.,Qingdao Agricultural University | Zhou S.,Key Laboratory of Integrated Crop Pests Management of Shandong Province | Liu Y.,Qingdao Agricultural University | Liu Y.,Key Laboratory of Integrated Crop Pests Management of Shandong Province | And 7 more authors.
European Journal of Plant Pathology | Year: 2016

Maize sheath blight is a destructive disease of maize world-wide. The causal pathogens of the disease include multinucleate, binucleate and uninucleate Rhizoctonia isolates according to the latest reports. In this study, the virulence and virulence factors of one uninucleate, two binucleate and nine multinucleate Rhizoctonia isolates were compared. The results showed that there was significant difference in the virulence of the tested Rhizoctonia isolates on maize, with multinucleate Rhizoctonia isolates the most virulent, binucleate Rhizoctonia isolates moderate and uninucleate Rhizoctonia isolate the lowest. The cell wall-degrading enzymes (CWDEs) and phytotoxins of the tested isolates were extracted and their enzymatic or biological activities were detected. The correlation coefficients between the enzymatic activity of polymethylgalacturonase (PMG), polygalacturonase (PG) and endo-β-1,4-glucanase (Cx) and pathogenicity of the isolates were 0.8210, 0.7314 and 0.8497, respectively. The correlation coefficients between the inhibition rate of corn seed germination and root growth caused by the phytotoxins and pathogenicity of the isolates were 0.9257 and 0.9690, respectively. These results indicated that CWDEs and phytotoxins likely act as virulence factors during infection. In conclusion, the lowest virulence of the uninucleate Rhizoctonia isolate JN on maize is possibly due to the low activities of CADEs and phytotoxins. © 2016 Koninklijke Nederlandse Planteziektenkundige Vereniging


Zhou S.,Qingdao Agricultural University | Zhou S.,Key Laboratory of Integrated Crop Pests Management of Shandong Province | Zhou S.,China Agricultural University | Zhang M.,Qingdao Agricultural University | And 20 more authors.
European Journal of Plant Pathology | Year: 2015

Plant-pathogenic Rhizoctonia spp. are soil-borne fungi with world-wide distribution. Most Rhizoctonia spp. are multinuclear and heterokaryotic fungi, which makes it difficult to build a stable transformation system. In this study, one uninucleate Rhizoctonia isolate, JN, was recovered from a field maize plant. Single nuclear status was observed under fluorescent microscopy after the hyphae were stained with Hoechst33258 solution. The optimal growth conditions of JN mycelia were 28 °C at pH7.0 on potato dextrose agar (PDA) media. The mycelial color of JN cultured on PDA turned from white to light brown with aging. Analysis of the internal transcribed spacer (ITS) sequence of the ribosomal DNA (rDNA) showed that there were two types of ITS sequences within the single isolate and the nucleotide identity of the two sequences is only 95 %. JN is more sensitive to SDS, PEG4000, Sorbitol, hydrogen peroxide (H2O2) and sodium chloride (NaCl) than a multinucleate Rhizoctonia solani, XN5, cultured on PDA. Given the single nucleus, JN has great potential to be used in fungal transformation. © 2015, Koninklijke Nederlandse Planteziektenkundige Vereniging.

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