SCREENING WORLD ONION GERMPLASM COLLECTION FOR RESISTANCE TO WHITE ROT

1978 ◽  
Vol 58 (3) ◽  
pp. 819-822 ◽  
Author(s):  
R. S. UTKHEDE ◽  
J. E. RAHE
Keyword(s):  
British Columbia ◽  
Allium Cepa ◽  
Germplasm Collection ◽  
Causal Agent ◽  
White Rot ◽  
Sclerotium Cepivorum ◽  
Muck Soil ◽  
Onion Germplasm

Two hundred and ninety-four accessions to the USDA world germplasm collection of Allium cepa were screened for resistance to Sclerotium cepivorum, the causal agent of white rot. The trial was conducted on organic muck soil in Burnaby, British Columbia, with uniformly high levels of added inoculum. Percent white rot infection in bulbs at harvest was measured and significant differences (P = 0.05) among the accessions occurred. High levels of resistance were found in at least three of the accessions, but none was immune.

SCREENING WORLD ONION GERMPLASM COLLECTION AND COMMERCIAL CULTIVARS FOR RESISTANCE TO SMUT

1980 ◽  
Vol 60 (1) ◽  
pp. 157-161 ◽  
Author(s):  
R. S. UTKHEDE ◽  
J. E. RAHE
Keyword(s):  
British Columbia ◽  
Allium Cepa ◽  
Germplasm Collection ◽  
Plant Introduction ◽  
Causal Agent ◽  
Commercial Cultivar ◽  
Commercial Cultivars ◽  
Muck Soil ◽  
Onion Germplasm

Two hundred and fifty-five accessions to the USDA world onion germplasm collection and 66 commercial cultivars of Allium cepa were screened for resistance to Urocystis magica, the causal agent of onion smut. The trial was conducted in Cloverdale, British Columbia on a muck soil heavily infested with U. magica. Percent smut infection in bulbs at harvest was measured and significant differences (P = 0.01) among the accessions and cultivars occurred. Three plant introduction lines and one commercial cultivar were completely resistant to U. magica in the trial and significant levels of resistance were found in six other plant introduction lines and one commercial cultivar.

scholarly journals Progress of White Rot on Garlic Cultivars Planted at Different Times

Plant Disease ◽  
1998 ◽  
Vol 82 (10) ◽  
pp. 1142-1146 ◽  
Author(s):  
Cleide M. F. Pinto ◽  
Luiz A. Maffia ◽  
Richard D. Berger ◽  
Eduardo S. G. Mizubuti ◽  
Vicente W. D. Casali
Keyword(s):  
Management Strategy ◽  
Allium Sativum ◽  
Average Duration ◽  
Minas Gerais ◽  
Causal Agent ◽  
White Rot ◽  
Sclerotium Cepivorum ◽  
Early Planting ◽  
Minas Gerais State ◽  
Epidemiological Parameters

In the region of Amarantina, Minas Gerais state, Brazil, four annual experiments with garlic (Allium sativum) were established in fields infested with Sclerotium cepivorum, causal agent of garlic white rot, to investigate the effect of time of planting on the day when disease was first noticed (tonset), incidence at harvest (yf), duration of epidemics (tf — tonset), and the response of five cultivars to white rot. Most epidemiological parameters were similar among cultivars. In 1986 to 1988, no white rot was observed on garlic planted during the warm temperatures in January. The average onset of white rot occurred at different times dependent on the day of planting as average temperatures decreased from January to May. That is, for February plantings, onset occurred after 93 to 140 days (between 1 June and 5 July); for March plantings, about 90 days (15 to 28 June); for mid-April plantings, about 77 days (1 July); and mid-May plantings, about 66 days (20 July). Because of these different times of onset, the average duration of epidemics was shorter for crops planted in February (30 days) compared to crops planted in March (48 days) or April to May (54 to 69 days). In general, most disease (highest incidence and longest duration) occurred on crops planted in March to May. Therefore, severe losses to white rot would be expected when garlic is planted at the traditional times (March and April) in areas infested with sclerotia of S. cepivorum. The early planting of garlic is recommended as an important management strategy to avoid white rot in areas with these infested soils.

White Rot of Garlic and Onion (Causal Agent, Sclerotium cepivorum): A Status Report from the Pacific Northwest

2013 ◽  
Vol 14 (1) ◽  
pp. 33
Author(s):  
Shari L. Lupien ◽  
Barbara C. Hellier ◽  
Frank M. Dugan ◽  
Linnea G. Skoglund ◽  
Karen F. Ward
Keyword(s):  
Pacific Northwest ◽  
Commercial Production ◽  
Causal Agent ◽  
White Rot ◽  
Status Report ◽  
Department Of Agriculture ◽  
Sclerotium Cepivorum ◽  
The Pacific ◽  
National Plant Germplasm System ◽  
First Time

There is evidence from literature, state department of agriculture documents, and recent diagnoses that Sclerotium cepivorum, causal agent of white rot of garlic and onion, is spreading and/or becoming more established in the Pacific Northwest. Previously documented distributions are summarized and the fungus is reported for the first time from Latah Co., ID; Pend Oreille Co., WA; and Lake, Sanders, and Missoula counties, MT. Although known from a tightly quarantined prior occurrence in the Idaho portion of Treasure Valley (southwest Idaho), the pathogen has not been formally reported from that state nor from the state of Montana. Latah Co. has commercial production of seed garlic and borders adjacent Whitman Co., WA, where the National Plant Germplasm System (NPGS) maintains North America's largest non-commercial collection of garlic and wild/ornamental onion. Strict phytosanitary protocols have been implemented on the NPGS farm. Various areas within the Pacific Northwest have long been important for commercial Allium production, and a list of state departments of agriculture regulations addressing white rot is presented for Idaho, Oregon, and Washington. Accepted for publication 18 February 2013. Published 19 June 2013.

Influence of onion seed bacterization on germination and mycosphere microflora of Sclerotium cepivorum sclerotia

1992 ◽  
Vol 38 (11) ◽  
pp. 1135-1143 ◽  
Author(s):  
M. S. Reddy ◽  
J. E. Rahe ◽  
C. A. Levesque
Keyword(s):  
Soil Surface ◽  
White Rot ◽  
Subtilis Strain ◽  
Bacterial Strains ◽  
Sclerotium Cepivorum ◽  
Seed Bacterization ◽  
Muck Soil ◽  
Onion Seed ◽  
Fungal Populations ◽  
Bacteria And Fungi

Diallyldisulfide (DADS) and onion seedlings grown from bacterized seeds significantly enhanced the germination of Sclerotium cepivorum sclerotia in muck soil compared with germination in the absence of seedlings or in the presence of seedlings grown from surface-sterilized nonbacterized seeds. Germination was greater for sclerotia on the soil surface than for buried sclerotia. When used for seed bacterization, Bacillus subtilis strain B-2 and four other bacterial strains obtained from rhizospheres of field-grown onions differed in their abilities to enhance germination of sclerotia. Strains B-2, UI-2, and B caused significantly greater germination of sclerotia than did strains UI-1 and W. Sclerotia in soil containing onion seedlings bacterized with B-2, UI-2, and B significantly supported reduced general indigenous bacterial and fungal populations. Treatment of soil with DADS reduced general indigenous bacterial but not fungal populations associated with sclerotia. There were significant inverse correlations between the proportions of sclerotia germinating and populations of bacteria and fungi associated with sclerotia of S. cepivorum. Key words: onion white rot, sclerotia, seed bacterization, mycosphere microflora, germination.

scholarly journals Evaluation of Long-day Onions for Resistance to White Rot Infection Using Greenhouse and Laboratory Techniques

2004 ◽  
Vol 129 (2) ◽  
pp. 258-265 ◽  
Author(s):  
Marilyn H.Y. Hovius ◽  
Irwin L. Goldman
Keyword(s):  
Disease Incidence ◽  
Aerial Mycelium ◽  
White Rot ◽  
Mycelium Growth ◽  
Field Screening ◽  
Sclerotium Cepivorum ◽  
Muck Soil ◽  
Field Reaction ◽  
Agar Media ◽  
Culture Growth

Breeders have found field screening for onion white rot resistance to be unreliable since consistently moderate to high disease levels that significantly differentiate cultivars, do not occur over field sites and years. The objective was to see if a greenhouse or laboratory technique could predict field reaction of onion accessions. Onion (Allium cepa) accessions were grown in fields naturally infested with the white rot causing fungus (Sclerotium cepivorum) in 1999 and 2000 (New Zealand) and in 2000 and 2001 (Canada). The field disease levels were low at three sites, moderate at two and high at one. Field screening was not a reliable predictor of white rot reaction when disease incidence was low. Onion accessions were screened for resistance in the greenhouse using nonsterile muck soil (NSMS) and sterile muck soil (SMS) with S. cepivorum sclerotia as the inoculum source. Total disease incidence was significantly higher in the NSMS compared to the SMS and accessions showed significant variability for white rot reaction in both soils. Two laboratory-based techniques were used to test the effect of onion volatiles on mycelium growth in culture. The volatiles from susceptible accessions resulted in faster radial growth of S. cepivorum mycelium (on water agar) and height of aerial mycelium (on potato dextrose agar) than volatiles from resistant accessions. Disease incidence in the greenhouse, S. cepivorum culture growth rates on water agar media and aerial mycelial height were all good predictors of field disease incidence in a covariance analysis. The best predictor was aerial mycelial height, which was predictive of field disease incidence in four out of six field sites. Onion breeders can use the methods described in this study in breeding for white rot resistance.

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