Detection of phythium spp. in gold course irrigation systems
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Many Pythium spp. are causal agents of disease on creeping bentgrass putting greens. Phytopathogenic Pythium spp. are known to disseminate through irrigation systems in agricultural settings, and this study provides evidence that Pythium spp. also disseminate through golf course irrigation systems. Water samples were collected from irrigation heads and water sources at ten golf courses in Missouri and Kansas. Samples were collected from 2018 to 2019 in April, July, and October. Phosphorus, nitrogen, and chloride concentrations were quantified for irrigation head samples taken each sampling month to determine if these parameters influence Pythium frequency. Pythium spp. were detected in samples through baiting and membrane filtration. Cultures were isolated on PARP media and DNA was extracted from putative Pythium isolates. ITS regions were PCR amplified, sequenced, and compared with Genbank accessions. Phylogenetic trees were constructed using representative sample sequences, sequences from seven morphologically identified reference isolates, and similar Genbank accessions. Detected species include Lagenidium giganteum, Pythium biforme, P. insidiosum, P. marsipium, P. plurisporium, and Saprolegnia hypogyna. Twenty-one clades lacked species-level resolution, and 14 of these clades were associated with Pythium species. Clades A, C, D, E, I, and M contain pathogenic Pythium species that cause root and crown rot on creeping bentgrass. Detected Pythium communities were dependent on the detection method used and sampling source. Pythium frequency and diversity were highest in April 2019. Sample temperature, sampling site, chloride, and nutrient concentrations did not influence Pythium frequency in samples. All irrigation systems that utilized surface water sources contained at least three Pythium spp. over the course of two years.