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Lamprecht S.C.,Agricultural Research Council Plant Protection Research Institute | Tewoldemedhin Y.T.,Agricultural Research Council Plant Protection Research Institute | Calitz F.J.,Agricultural Research Council Biometry Unit | Mazzola M.,Tree Fruit Research Laboratory
European Journal of Plant Pathology | Year: 2011

Several methods with potential for the management of Rhizoctonia diseases of canola and lupin including plant resistance, fungicide seed treatment and biological control using binucleate Rhizoctonia anastomosis groups (AGs) were evaluated under glasshouse conditions. Screening included the examination of resistance of eight canola and eight lupin cultivars/selections to damping-off and hypocotyl/root rot caused by the multinucleate Rhizoctonia solani AG-2-1, 2-2, 4 and 11. All canola cultivars were highly susceptible to AG-2-1, but Rocket, Spectrum and 44C11 were more resistant than the other cultivars. Spectrum and 44C73 were also more resistant to AG-4 than the other canola cultivars. On lupin, R. solani AG-2-2 and 4 were most virulent, and the cultivar Cedara 6150 and selection E16 were most resistant to AG-2-2; Cedara 6150, E16, Mandelup and Quilinock were more resistant to AG-4 than the other cultivars/selections. The Lupinus luteus selections, E80.1.1.2 and E82. 1. 1 were most susceptible to AG-2-2, 4 and 11. Seed treatment with the fungicides Cruiser OSR (a.i. difenconazole, fludioxonil, metalaxyl-M, thiamethoxam) and SA-combination (a. i. iprodione, metalaxyl, thiram) significantly increased survival of canola and lupin seedlings, decreased hypocotyl/root rot and improved the percentage of healthy seedlings, with the SA-combination being significantly more effective than Cruiser OSR. Application of the binucleate Rhizoctonia AGs (A, Bo, K and I) significantly increased the survival of lupin seedlings inoculated with R. solani AG-2-2 and 4, and AG-I and K significantly improved survival of canola in the presence of AG-4. This is the first report of the potential of binucleate AGs to protect canola and lupin seedlings against infection by multinucleate AGs. © 2011 KNPV.

Lamprecht S.C.,Agricultural Research Council Plant Protection Research Institute | Tewoldemedhin Y.T.,Agricultural Research Council Plant Protection Research Institute | Hardy M.,Private Bag X1 | Calitz F.J.,Agricultural Research Council Biometry Unit | Mazzola M.,Tree Fruit Research Laboratory
European Journal of Plant Pathology | Year: 2011

Rhizoctonia spp. anastomosis groups (AGs) associated with canola and lupin in the southern and western production areas of the Western Cape province of South Africa were recovered during the 2006 and 2007 growing seasons and identified using sequence analyses of the rDNA internal transcribed spacer regions. The effect of crop rotation systems and tillage practices on the recovery of Rhizoctonia spp. was evaluated at Tygerhoek (southern Cape, Riviersonderend) and Langgewens (western Cape, Moorreesburg) experimental farms. Isolations were conducted from canola planted after barley, medic/clover mixture and wheat, and lupin planted after barley and wheat, with sampling at the seedling, mid-season and seedpod growth stages. In the 2006 study, 93. 5% of the Rhizoctonia isolates recovered were binucleate and 6. 5% multinucleate; in 2007, 72. 8% were binucleate and 27. 2% were multinucleate. The most abundant AGs within the population recovered included A, Bo, I and K, among binucleate isolates and 2-1, 2-2 and 11 among multinucleate isolates. Crop rotation sequence, tillage and plant growth stage at sampling all affected the incidence of recovery of Rhizoctonia, but certain effects were site-specific. The binucleate group was more frequently isolated from lupin and the multinucleate group from canola. AG-2-1 was only isolated from canola and AG-11 only from lupin. This study showed that important Rhizoctonia AGs such as AG-2-1, 2-2 and 11 occur in both the southern and the western production areas of the Western Cape province and that crop rotation consistently influences the incidence and composition of the Rhizoctonia community recovered from the cropping system. © 2011 KNPV.

Tewoldemedhin Y.T.,Western Research Institute | Lamprecht S.C.,Western Research Institute | Mazzola M.,Tree Fruit Research Laboratory
Plant Disease | Year: 2015

Rhizoctonia spp. associated with rooibos in the Western Cape province of South Africa were recovered during the 2008 season by planting seedlings in rhizosphere soils collected from 14 rooibos nurseries. In all, 75 Rhizoctonia isolates were obtained, of which 67 were multinucleate and 8 were binucleate Rhizoctonia spp. The identity of these isolates to anastomosis group (AG) was determined through sequence analysis of the ribosomal DNA internal transcribed spacer region. The collection of multinucleate isolates included representatives of AG-2-2 (67%), AG-4 HGI (14%), AG-11 (5%), and R. zeae (3%). Binucleate AGs included AG-Bo (4%) and AG-K (4%) and an unidentified binucleate Rhizoctonia (3%). Rhizoctonia solani AG-2-2 was the most widely distributed species of Rhizoctonia detected among the 11 nurseries sampled. All AGs recovered from rooibos have been previously reported on crop plants in South Africa, with the exception of R. zeae. However, this is the first study to classify the Rhizoctonia AGs recovered from rooibos. In glasshouse bioassays, the most virulent Rhizoctonia AGs on rooibos and lupin were AG-2-2, AG-4 HGI, and AG-11. Although plant damage was less than that observed for lupin and rooibos, oat was significantly affected by AG-2-2 and AG-4 HGI. Two composts sourced from independent suppliers were evaluated for disease suppression under glasshouse conditions. Compost amendment suppressed damping-off by most R. solani AGs, except for AG-4 HGI. Furthermore, within AG-2-2, suppression by compost was isolate specific. © 2015 The American Phytopathological Society.

Wang D.,University of Illinois at Urbana - Champaign | Korban S.S.,University of Illinois at Urbana - Champaign | Pusey P.L.,Tree Fruit Research Laboratory | Zhao Y.,University of Illinois at Urbana - Champaign
Phytopathology | Year: 2011

RcsC is a hybrid sensor kinase which contains a sensor domain, a histidine kinase domain, and a receiver domain. We have previously demonstrated that, although the Erwinia amylovora rcsC mutant produces more amylovoran than the wild-type (WT) strain in vitro, the mutant remains nonpathogenic on both immature pear fruit and apple plants. In this study, we have comparatively characterized the Erwinia RcsC and its homologs from various enterobacteria. Results demonstrate that expression of the Erwinia rcsC gene suppresses amylovoran production in various amylovoran overproducing WT and mutant strains, thus suggesting the presence of a net phosphatase activity of Erwinia RcsC. Findings have also demonstrated that rcsC homologs from other enterobacteria could not rescue amylovoran production of the Erwinia rcsC mutant in vitro. However, virulence of the Erwinia rcsC mutant is partially restored by rcsC homologs from Pantoea stewartii, Yersinia pestis, and Salmonella enterica but not from Escherichia coli on apple shoots. Domain-swapping experiments have indicated that replacement of the E. coli RcsC sensor domain by those of Erwinia and Yersinia spp. partially restores virulence of the Erwinia rcsC mutant, whereas chimeric constructs containing the sensor domain of E. coli RcsC could not rescue virulence of the Erwinia rcsC mutant on apple. Interestingly, only chimeric constructs containing the histidine kinase and receiver domains of Erwinia RcsC are fully capable of rescuing amylovoran production. These results suggest that the sensor domain of RcsC may be important in regulating bacterial virulence, whereas the activity of the histidine kinase and receiver domains of Erwinia RcsC may be essential for amylovoran production in vitro. © 2011 The American Phytopathological Society.

Shin S.-B.,Colorado State University | Shin S.-B.,Tree Fruit Research Laboratory | Golovkin M.,Colorado State University | Golovkin M.,Technology and Research | Reddy A.S.N.,Colorado State University
Scientific Reports | Year: 2014

Previous genetic studies have revealed that a pollen-specific calmodulin-binding protein, No Pollen Germination 1 (NPG1), is required for pollen germination. However, its mode of action is unknown. Here we report direct interaction of NPG1 with pectate lyase-like proteins (PLLs). A truncated form of AtNPG1 lacking the N-terminal tetratricopeptide repeat 1 (TPR1) failed to interact with PLLs, suggesting that it is essential for NPG1 interaction with PLLs. Localization studies with AtNPG1 fused to a fluorescent reporter driven by its native promoter revealed its presence in the cytosol and cell wall of the pollen grain and the growing pollen tube of plasmolyzed pollen. Together, our data suggest that the function of NPG1 in regulating pollen germination is mediated through its interaction with PLLs, which may modify the pollen cell wall and regulate pollen tube emergence and growth.

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