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Management of seedling diseases caused by Oomycetes, Phytophthora spp., Phytopythium spp. and Pythium spp. using seed treatment in Ohio.

Vargas, Amilcar
http://rave.ohiolink.edu/etdc/view?acc_num=osu1524060260234098

Abstract Details

2018, Master of Science, Ohio State University, Plant Pathology.
Watermolds that affect soybean seed and seedlings contribute to significant losses each year due to reduced plant population and yield. In Ohio, Pythium and Phytophthora populations are diverse, with more than 30 species of Pythium being recovered from symptomatic soybean seedlings. This includes species of Pythium that were recently reclassified as Phytopythium. Fungicide seed treatments and host resistance are the main strategies to manage seedling diseases caused by watermolds in Ohio. The reduced sensitivity of watermold populations towards the current active ingredients in the market has led to an increased interest to identify and evaluate new active ingredients. The objectives of this study were to evaluate the efficacy of oxathiapiprolin alone or in combination with metalaxyl/mefenoxam or ethaboxam as a soybean seed treatment and the pathogenicity of Phytopythium mercuriale on three soybean cultivars with different levels of resistance towards watermolds. Oxathiapiprolin was evaluated through lab, greenhouse, and field-based studies at 14 different environments across Ohio. In amended agar plates inoculated with different species of watermolds, oxathiapiprolin significantly limited mycelial growth of Phytopythium helicoides, Phy. litorale, Phytopythium delawarense, Phy. mercuriale, Phytophthora sojae and Phytophthora sansomeana, but not Pythium torulosum, Py. ultimum var. ultimum, Py. lutarium, Py. attrantheridium, Py. inflatum, Py. oopapillum, Py. diclinum, Py. pleroticum, Py. heterothallicum, Py. nodosum, Py. middletonii and Py. dissotocum. In a greenhouse cup assay, there was no significant difference between the non-treated and seed treated with oxathiapiprolin (P > 0.05) that was inoculated with Pythium spp. In field based studies there was a significantly higher number of plants per hectare in 5 of 10 environments and yield (kg/ha) in 6 of 10 environments when seed of a moderately susceptible cultivar was treated with oxathiapiprolin alone or in combination with metalaxyl/mefenoxam or ethaboxam. Early plant population and yield (kg/ha) were also significantly (P < 0.05) higher for 6 of 7 cultivars in at least 1 of 4 environments. These results indicate that oxathiapiprolin can be used to protect soybean plant establishment and yield in regions prone to heavy rains shortly after planting where diseases caused by Phytophthora and Phytopythium are prevalent. Care should be taken to combine oxathiapiprolin with another active ingredient targeting species of Pythium. Based on a seed plate and seedling root rot experiments, Phytopythium mercuriale isolates collected in Ohio, significantly inhibited germination, reduced seed health, and caused seedling root rot on soybean. Based on the distribution in North America including, Arkansas, Kansas, Nebraska, Ontario and now Ohio, this is a specie that requires more evaluation and most likely has a wider distribution and host range.
Anne Dorrance (Advisor)
Melanie Lewis Ivey (Committee Member)
Pierce Paul (Committee Member)
107 p.
Agricultural Chemicals; Agriculture; Agronomy; Plant Pathology
Watermolds; Pythium; Phytophthora; Phytopythium

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Citations

  • Vargas, A. (2018). Management of seedling diseases caused by Oomycetes, Phytophthora spp., Phytopythium spp. and Pythium spp. using seed treatment in Ohio. [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524060260234098

    APA Style (7th edition)

  • Vargas, Amilcar. Management of seedling diseases caused by Oomycetes, Phytophthora spp., Phytopythium spp. and Pythium spp. using seed treatment in Ohio. . 2018. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1524060260234098.

    MLA Style (8th edition)

  • Vargas, Amilcar. "Management of seedling diseases caused by Oomycetes, Phytophthora spp., Phytopythium spp. and Pythium spp. using seed treatment in Ohio. ." Master's thesis, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524060260234098

    Chicago Manual of Style (17th edition)

osu1524060260234098
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