Screening of USDA Onion Germplasm for Fusarium Basal Rot Resistance

Fusarium basal rot (FBR) caused by oxysporum f. sp. cepae (FOC) is a major threat to onion (Allium cepa L.) production and marketing worldwide. Finding new sources of FBR-resistance develop synthetic cultivars priority for breeders. As there are no FBR-resistant short-day cultivars, 85 U.S. National Plant Germplasm System plant introduction accessions that originated from 23 different countries were screened their FBR susceptibility. To compare susceptibility these at seedling mature bulb stages, susceptible check cultivar, NuMex Crimson, partially resistant Serrana its selected population, Serrana-sel, included in the study. The screening was performed after inoculating silica-sand media with virulent FOC isolate ‘CSC-515’ 1.0 × 104 macroconidia g−1 sand. Each entry evaluated twice growth chambers, percent survival adjusted number seedlings germinated uninoculated trays. Mature bulbs produced field transversely cut plates potato dextrose agar plugs containing spores same 3.0 mL−1. severity incidence then calculated 20 days incubation. Significant variation found among FBR-susceptibility (p < 0.001) both stages. Two sets 18 identified either higher or compared checks. Among them, PI 256326 (‘Baia Periforme’, originator cultivar ‘Serrana’) had than checks, lower check. Another accession, 656956 (‘S015’), exhibited low (4.3 on 1 9 scale) (41.7%). These two accessions, which known previously high intra-population heterogeneity root resistance FBR, respectively, show promise incorporating into cultivars. rankings could vary future studies range isolates due interaction as observed past studies.