Browsing by Subject "Rhizoctonia"

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    2022 SMBSC--Management of Rhizoctonia Diseases in Sugarbeet
    (2022) Chanda, Ashok
    Rhizoctonia seedling damping-off and root rot diseases are prevalent in southern Minnesota sugarbeet growing areas. Utilization of soybeans and corn as rotation crops with sugarbeet will increase the risk for Rhizoctonia diseases and ultimately cause significant yield loss and loss of revenue to the sugarbeet growers. This presentation covers various strategies that were tested under field conditions in 2021 and previous years at the Northwest Research and Outreach Center, Crookston, MN. Rhizoctonia mitigation techniques included in this presentation are useful to successfully manage Rhizoctonia diseases in southern Minnesota growing area.
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    Evaluation of resistance to Rhizoctonia solani in soybean and assessment of fungicide sensitivity in isolates from sugar beet and soybean
    (2020-06) Sharma, Pratibha
    Soybean and sugar beet are commonly grown in rotation in the Red River Valley of MN and ND and southern Minnesota. Both crops are highly susceptible to Rhizoctonia solani. Currently there are no Rhizoctonia resistant soybean cultivars available to the growers. Partially resistant commercial sugar beet cultivars are available, but they are susceptible to R. solani during the seedling stage. Disease management for both crops relies partially on the use of fungicides. The primary objectives of this study were (i) to determine the response of different soybean genotypes to R. solani in the field and growth chamber, and (ii) to determine the sensitivity of R. solani isolates from soybean and sugar beet to the fungicides sedaxane, penthiopyrad, fluxapyroxad, azoxystrobin, and pyraclostrobin. Soybean genotypes were evaluated for their response to R. solani at Waseca and Crookston, MN field locations. All genotypes evaluated at Crookston (n=20) in 2018 and 2019 had high losses in inoculated plots in plant population and yield compared to noninoculated control plots. Losses were also severe for all genotypes (n=36) at Waseca in 2018. Some soybean genotypes had relatively low losses in 2017 and 2019, however, their performance was not consistent across the years. MN 1613CN was the only genotype that performed well in 2017 and 2019, but it had high plant population and yield losses in 2018. Significant genotype by isolate interaction was detected when 16 soybean genotypes were evaluated for their response to four isolates of R. solani in the growth chamber. All genotypes were highly susceptible to isolate Rs 16WC3-2, but they differed in susceptibility to some other isolates. The soybean genotypes used in this study were not resistant to R. solani, but those with relatively low losses in plant population should be investigated further along with additional genotypes. The response of soybean genotypes to R. solani is strongly influenced by the isolate and environment, so future studies should continue to be conducted under different environmental conditions using multiple isolates. Sensitivity of R. solani AG 2-2 isolates (n=35) collected from soybean and sugar beet to the SDHI fungicides sedaxane, penthiopyrad, and fluxapyroxad, and to the QoI fungicides pyraclostrobin and azoxystrobin was determined using a mycelial growth inhibition method. The concentration of fungicide required to inhibit the radial growth of mycelium 50% (EC50) compared to the growth on non-amended media was estimated for each isolate. The mean and range of EC50 values for sedaxane, penthiopyrad, fluxapyroxad and pyraclostrobin were 0.1 (0.03 to 0.3), 0.15 (0.05 to 0.27), 0.16 (0.08 to 0.3), and 0.24 (0.04 to 1.02) µg a.i./mL, respectively. The mean EC50 values of azoxystrobin for 22 isolates ranged from 0.76 to 2.36 µg a.i./mL. EC50 values for azoxystrobin could not be estimated for 13 isolates due to < 50% inhibition in growth, however, a pronounced decrease in mycelial density was observed as fungicide concentration increased. The SDHI fungicides and pyraclostrobin effectively inhibited the growth of the isolates of R. solani in vitro at low concentrations, but new methods are needed to determine in vitro sensitivity to azoxystrobin. In summary, the different levels of partial resistance to R. solani detected in soybean genotypes suggest a need for improving resistance to R. solani, and fungicide sensitivity results indicate that currently labeled fungicides continue to be useful in managing seedling damping-off and root rot.
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    Interaction of temperature, soil moisture, seed treatment, cultivar, and soybean cyst nematode in root rot of soybean.
    (2011-04) Meyer, Paul Wells
    The root rot complex comprised of Fusarium species, Rhizoctonia solani, Phytophthora sojae, and Pythium species is a major contributor to yield loss in soybean. Due to its wide distribution, Fusarium solani is possibly the most important contributor to losses caused by this complex in Minnesota. Heterodera glycines, commonly known as soybean cyst nematode (SCN), is the most destructive soilborne pathogen of soybean. Yield losses to Fusarium root rot and SCN for 2005 in Minnesota were estimated to be 85,000 tons and 250,000 tons, respectively. The etiology of seed, seedling, and root rots of soybean in Minnesota is poorly understood, and the interactions between the major root infecting pathogens of soybean are even less well understood. Root rot of soybean during germination and emergence is a major cause of stand establishment problems. Seed treatment fungicides have provided inconsistent control of pre-emergence seed, seedling, and root rot during field trials in Minnesota, and cultivars resistant to native isolates of F. solani are not available. Previous studies have investigated the interaction between SCN and Fusarium virguliforme, but not between SCN and F. solani. This is important, since SCN is prevalent in agricultural soils in Minnesota. My objectives were to (1) determine the relationship between soil temperature and moisture in root infection by Fusarium spp., Pythium spp., P. sojae, and Rhizoctonia spp. in natural soil samples taken from soybean fields in Minnesota, (2) determine the frequency of root infection as a function of seed treatment and sampling time after planting in natural soil, and the soil temperature and moisture conditions at which seed treatments are effective (or not effective), (3) determine the predominant native Fusarium species infecting soybean in Minnesota soil as a function of temperature and soil moisture, (4) screen soybean varieties in maturity group 2 and earlier for partial resistance to Fusarium spp. naturally present in soil, and for partial resistance to an isolate of F. solani artificially inoculated in sterile sand, and (5) determine the effect of soybean taproot infection by an isolate of F. solani on secondary root tip infection by SCN, and vice versa.
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    Management of Rhizoctonia Diseases in Sugarbeet
    (2022-01-15) Chanda, Ashok
    Rhizoctonia seedling damping-off and root rot diseases are prevalent in Minnesota and North Dakota and can cause significant yield loss and loss of revenue to sugarbeet growers. This presentation covers various strategies that were tested under field conditions in 2021 at the Northwest Research and Outreach Center, Crookston, MN. Rhizoctonia mitigation techniques included in this presentation are useful to successfully manage Rhizoctonia diseases in the field.
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    Rhizoctonia Management in Sugarbeet 2021 SMBSC Seminar
    (2021-01-25) Chanda, Ashok, K; achanda@umn.edu; Chanda, Ashok, K; UMN Sugarbeet Pathology Lab
    Research from 2020 field trials and recommendations for managing Rhizoctonia in sugarbeet in 2021 presented at the SMBSC grower seminar on Jan 22, 2021 by Ashok Chanda