Testing a breeding strategy to select for resistance to onion basal rot caused by Fusarium oxysporum f.sp. cepae in Argentina

CIOTTI, L.; CALIGIORE GEI, P; VALDEZ, J.; GALMARINI, C.R.

Madison

Simposio; NOA/NARC/IARS Research Conference. Madison, WI, USA. July 2019.; 2019

USDA/UW-Madison/NOA

Fusarium basal rot (FBR) is one of the main onion diseasesworldwide and also in Argentina. The Onion National Breeding Program, held atINTA La Consulta, Argentina, has developed breeding lines tolerant to FBR usingrecurrent selection under field conditions; the individuals that show lowerseverity are the ones selected each generation. The aim of the present work wasto test this selection strategy in controlled conditions.  Three hundred and seventy two seeds of abreeding line (P0) were sown in caps inoculated with Fusarium oxysporum (isolate LJC10081), oneseed per cap. After 15 days 162 surviving plants were treated with fungicideand transplanted to containers with sterile substrate. These plants producedbulbs that were planted for seed production in isolation; the obtained seeds werelabelled as PCC. At the same time seeds of P0 were grown under fieldconditions in a FBR-conductive soil. The bulbs were selected at harvest basedon FBR score, root system quality and agronomic features. Selected bulbs producedseeds that were labelled as PFC. Seeds of P0, PCC and PFC were comparedin controlled conditions for FBR resistance. The area under disease progresscurve was significantly reduced in PFC/PCC, compared to the original P0,even at high inoculum concentrations. Disease progression was delayed and lowerrates were achieved in PCC. The evaluation under controlled conditionsconfirmed the progress that has been made selecting under field conditions,besides the described lab selection technique may constitute a useful tool to selectmaterials that carry genetic resistance.