P-550 - Survey and Molecular Characterization of the Pecan scab pathogen Venturia effusa in Oklahoma

Pecan (Carya illinoinensis) is an important tree nut that is native to the southern US and northern Mexico, with a recent upsurge in global production.  Oklahoma is among the leading pecan-producing states in the US. However, pecan production is hampered by diseases, with pecan scab, caused by Venturia effusa, the most important disease wherever pecan is grown. However, there is little information on the genetic diversity and population structure of V. effusa in Oklahoma. This study aims to survey and characterize the population of V. effusa in Oklahoma. A statewide survey was initiated in 2024 where symptomatic pecan leaves, shucks, and nuts were collected from  orchards in Oklahoma.  Samples were surface-sterilized, plated on oatmeal agar (OA) for sporulation, and incubated at 25°C for 14–21 days. V. effusa colonies appeared dark olive-green to black with slow growth, while other fungi varied in color. Mycelium was transferred to potato dextrose agar (PDA) for pure cultures. Genomic DNA was extracted using the CTAB method for molecular characterization. Molecular identification was carried out by Sanger sequencing of purified PCR amplifications of the ITS, β-tubulin, RPB2  genes. Sequence analyses identified variations in the recovered Venturia effusa isolates. Additional surveys and characterization are ongoing. Our study provides an improved understanding of the population of V. effusa in Oklahoma, which will improve understanding of pathogen epidemiology and lay the foundation for subsequent characterization of fungicide sensitivities.