ISHS Acta Horticulturae 637: XXVI International Horticultural Congress: Advances in Vegetable Breeding
SCREENING SHORT-DAY ONION VARIETIES FOR RESISTANCE TO FUSARIUM BASAL ROT |
| Authors: | J.A. Lopez, C.S. Cramer |
| Keywords: | Allium cepa, disease screening, Fusarium oxysporum, onion breeding |
| DOI: | 10.17660/ActaHortic.2004.637.19 |
| Abstract:
Fusarium basal rot (FBR), causal organism Fusarium oxysporum f. sp. cepae, is a worldwide soil-borne fungal disease that affects bulb onions (Allium cepa L.). Short and intermediate-day onion cultivars that are resistant to FBR are lacking. Breeding efforts are underway to develop resistant cultivars. The goal of this project was to screen short-day onion germplasm for FBR resistance using an inoculated seedling screening in a growth chamber and a mature bulb field screening. In growth chambers, forty-two short-day onion lines were seeded in silica sand infested with 4.0 x 104 spores. g-1 sand. At two weeks, the number of germinated seedlings was counted and the chamber temperature was increased from 22°C to 28°C. At four weeks, the number of surviving seedlings was counted and a percent survival rate was calculated for each line. The same onion lines were grown in a field known to produce a high incidence of fusarium-basal-rot-infected bulbs. When all the bulbs in a plot were mature, the basal plates of 30 bulbs were cut transversely and each plate was rated for disease severity on a scale of 1-9. The FBR incidence was calculated from the number of bulbs with FBR out of total bulbs tested. In growth chamber studies, ‘NuMex Luna’ and NMSU 00-32 had the highest seedling survival rate (23.6% an 20.4% respectively). In field studies, ‘Cardinal’ was found to have the highest FBR incidence (90.8%) and the highest FBR severity (4.9). ‘NMSU 00-13-1’ was found to have the lowest FBR incidence (10%) and the lowest FBR severity (1.11). A strong, positive correlation existed between FBR incidence and severity, whereas both traits were weakly correlated with seedling survival. | |
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