SCREENING OF ONION SEEDLINGS FOR RESISTANCE AGAINST NEW MEXICO ISOLATES OF FUSARIUM OXYSPORUM f sp CEPAE
A. Saxena , C.S. Cramer
New Mexico onion fields face reduced plant stand due to killing of seedlings for autumn-sown crop due to Fusarium basal rot (FBR). The goal of this study was to screen FBR-resistant and FBR-susceptible seedlings of onion entries using multiple Fusarium oxysporum f. sp. cepae (FOC) isolates collected from onion production fields in New Mexico. Twenty seeds from eight onion entries each were placed on a moist paper towel inside a Petri plate with a 1 cm2 piece of mycelial plug from one FOC isolate. A total of 136 combinations of FOC isolates and onion entries were evaluated at 25°C for 20 days for two years and disease incidence was calculated. An analysis of variation demonstrated a significant interaction between FOC isolate and onion entry for FBR incidence. Onion entries ‘NuMex Chaco’ and ‘NuMex Crispy’ produced the greatest spread in FBR incidence values for the FOC isolates tested. FOC isolate ‘CSC 515’ was the best FOC isolate for future screenings based upon its high mean and variation of FBR incidence.