2018 ASHS Annual Conference

White rust is an economically important diseases of spinach (Spinacia oleracea) caused by Albugo occidentalis, which is epidemic in spinach production areas of the central and eastern United States. A total of 440 spinach genotypes including 400 USDA germplasm accessions and 40 Arkansas spinach breeding lines were evaluated for white rust resistance during the 2016-17 and 2017-18 winter seasons at the Del Monte White Rust Nursery in Crystal City, TX where heavy disease pressure has consistently been observed for 30 years. Each accessions was naturally inoculated. Disease reactions of the each accession were evaluated at the before bolting stage in the trial. Percentage leaf infection was assessed visually using a 0–9 scale (0 = no disease symptom, 1 ≤ 10%, 2 ≤ 20%, 3 ≤ 30%, 4 ≤ 40%, 5 ≤ 50%, 6 ≤ 60%,7 ≤ 70%, 8 ≤ 80% and 9 ≥ 90%). The results showed that ten accessions (CPPSIH 3 03, NSL 6098,PI 175311,PI 220686,PI 224959,PI 226671,PI 227045,PI 648958,PI 662302 and PI 677114) exhibited resistant to white rust (90% or more of leaf area are not got infected). By selection under heavy disease pressure, ten UARK breeding lines (08-03-316-1, 08-269-1, 08-275, 08-301-2, 08-321, 08-88-310, 08-198, 08-143-1, 08-103, 03-316-7) exhibit high resistant to white rust, their true leaves almost do not get infected and show symptoms. These resistant genotypes provide a valuable resource for functional gene exploration and as a source of white rust resistance for breeding programs.