Articles
SCREENING SHORT-DAY ONION VARIETIES FOR RESISTANCE TO FUSARIUM BASAL ROT
Article number
637_19
Pages
169 – 173
Language
English
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.
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.
Authors
J.A. Lopez, C.S. Cramer
Keywords
Allium cepa, disease screening, Fusarium oxysporum, onion breeding
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