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Pythium and Phytopythium associated with Soybean in Buenos Aires (Argentina).

Pablo Grijalba: Univ. de Buenos Aires

<div><em>Pythium </em>and <em>Phytopythium</em> cause seed and root rot, and damping off in diverse plant species. The aim of this research was to identify these pathogens associated with soybean in Argentina. From 2013 to 2016, 85 soybean production fields were surveyed in Northern (NBA) and South-Eastern (SEBA) Buenos Aires Province. Isolates were obtained from seedlings and soil, and also from harvested seeds, using selective media. The isolates were characterized by classical and molecular methods. From seedlings and soil, from NBA 181 isolates were recovered which corresponded to 8 species of <em>Pythium</em>:<em> ultimum, irregulare, sylvaticum, inflatum, aphanidermatum, dissotocum, catenulatum, longandrum </em>and<em> P. </em>sp., and to 4 species of <em>Phytopythium: helicoides</em>,<em> frezium sp. </em>nov.,<em> chamaehyphon </em>and<em> Phy. s</em>p. <em>P. ultimum</em> and <em>P. irregulare</em> were the most abundant (41,7% and 22,5% respectively). From SEBA, 102 isolates were recovered, which belonged to <em>Pythium</em>: <em>ultimum, irregulare, sylvaticum </em>and<em> paroecandrum,</em> being the first two the most abundant (66,4% y 23,2% respectively). From seeds, 2 isolates, <em>P.</em> <em>sylvaticum </em>and<em> P. nunn, </em>were obtained from SEBA, and 30 from NBA, identified as <em>P. irregulare, P. paroecandrum, P. heterothallicum, P. acanthicum, P. </em>sp<em>. </em>and <em>Phy. vexans</em>. The isolates presented different degrees of pathogenicity, ranging from highly pathogenic to non-pathogenic. This is the first report of <em>P. </em><em>nunn</em><em>, P. longandrum, P. paroecandrum</em> and <em>P. heterothallicum, </em>in Argentina.</div>