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Temporal and host driven variation of Pythium and Globisporangium populations in chrysanthemum and geranium
Maria Proano: Oklahoma State University; Christian Ayala: Universidad de las Fuerzas Armadas ESPE; Adriana Chiriboga: Universidad de las Fuerzas Armadas ESPE; Patricia Garrido: AGROCALIDAD; Edinson Diaz: Oklahoma State University; Stephen Marek: Oklahoma State University; Hassan Melouk: USDA ARS; Margery Daughtrey: Cornell University; Carla Garzon: Oklahoma State University
<div>Multiple <i>Pythium</i> and <i>Globisporangium</i> species cause damping off of seedlings, seed rot, stem lesions, and root rot in greenhouse ornamental crops. To identify the diversity of species present in floricultural greenhouses located in Long Island, New York, two hundred seven isolates were collected from <i>Chrysanthemum</i> L. plants in 2014. Analysis of DNA sequences based on ITS region identified fifteen species of <i>Globisporangium </i>(n=4) and <i>Pythium</i> (n=11). The <i>G. irregulare</i> s.l. complex (n=120) were the most prevalent plant pathogenic species, which agrees with results of previous studies on <i>Pelargonium</i> spp. and other spring crops (2011 - 2013). Moderate to high genetic structure was found between greenhouse populations for each species of the <i>G. irregulare</i> complex. Analysis of Molecular Variance (AMOVA), Principal Coordinates Analysis (PCoA) and minimum spanning networks (MSN) suggest local sources of inoculum as well as shared sources of inoculum for Pythium diseases of chrysanthemum. When genotypes of <i>G. irregulare</i> s.l. from Geranium were associated by MSN over different seasons and years (2011-2013), closely related genotypes occurred in the same location over different years, suggesting inoculum may have survived in greenhouse populations from year to year. Scouting propagative materials and immediate eradication of symptomatic plants, as well maintaining good greenhouse sanitation practices are needed to minimize movement and survival of inoculum in floricultural greenhouses.</div>

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