P-484 - Isolation Techniques and Media Selection for Globisporangium ultimum from Field Crops in West Tennessee

Several soil-borne oomycete pathogens cause pythium seed rots, and Globisporangium ultimum (formerly Pythium ultimum), is a primary concern. These pathogens thrive in moist soils, under wide temperature ranges, leading to stand loss, notably in corn, soybean, and cotton, which are commonly rotated in the Southeastern U.S. Given that G. ultimum is a soil-borne pathogen, isolation techniques such as soil dilution plating and root plating plus media selection are crucial for collecting isolates while suppressing the growth of true fungi. However, some growth mediums for oomycetes also allow the growth of true fungi such as Mortierella spp., Rhizopus spp., and Mucor spp.  This study aims to investigate optimal media and collection techniques for isolating G. ultimum. The media types to be assessed include PDA + Streptomycin, PARP amended with two different rates of Tebuconazole, and P5ARP. The growth of G. ultimum will be compared against three common contaminating true fungi, by measuring colony growth over time. A greenhouse study will also be conducted using soil infested with G. ultimum to evaluate pathogen collection techniques from soil and root tissue from cotton seedlings. Collection techniques to be evaluated include using soil dilution plating with bulk and rhizosphere soil and root plating to evaluate the recovery of G. ultimum colonies. Future directions include collecting and identifying other oomycete species from soils across the cotton belt and pathogenicity seed assays using corn, cotton, and soybean against the collected isolates.