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Influence of temperature on the isolation of water molds using a soil bating technique

Krystel Navarro: The Ohio State University

<div>Water molds (<em>Pythium </em>and<em> Phytophthora </em>spp<em>.)</em> can cause pre- and post-emergence damping-off of seed and seedlings in soybean. Very wet environmental conditions favor disease development however, varying temperature profiles have been reported. Thus, our objective was to investigate the effects of temperatures on the isolation of water molds using a soil bating technique and compare a culture dependent isolation method (CDIM) to an amplicon-based metagenomics approach (ABMA). Soils collected from soybean fields in northern Ohio were placed in 17.8cm pots, flooded for 24 h and incubated for two week at 15<sup>◦</sup>C or 25<sup>◦</sup>C. A susceptible cultivar was then introduced and symptomatic seedlings collected after 4d. For the CDIM, seedling roots were washed and plated on PIBNIC selective media and corresponding rhizospheric soil collected for the ABMA. The ITS 1 region was then amplified. Sanger sequencing was used to identify isolates collected using the CDIM, while for the ABMA, Illumina Mi-seq was performed. From our CDIM, <em>Pythium sylvaticum</em> and <em>P. ultimum </em>var<em>. ultimum</em> were the most frequently recovered species at both temperatures. However, <em>P. hypogynum, P. heterothallicium, P. inflatum and P. middletoni </em>were only recovered<em>,</em> at 25<sup>◦</sup>C and, <em>P. torulosum</em> was only recovered at 15<sup>◦</sup>C. Furthermore, when using ABMA, we were able to identify a greater amount of water mold species including 20 <em>Pythium spp.</em> and 2 <em>Phytophthora spp</em>. demonstrating a greater depth in detection when multiple species with similar morphology are present in the field. Temperatures also seemed to influence species diversity and abundance when using a soil bating technique.</div>