PRELIMINARY EVALUATION OF In vitro SECONDARY METABOLITES OF Sclerotium cepivorum, THE CAUSAL AGENT OF ONION WHITE ROT

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.

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

Plant Health Progress ◽

10.1094/php-2013-0619-01-rv ◽

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.

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Sclerotial morphogenesis in Sclerotium cepivorum in vitro

Canadian Journal of Botany ◽

10.1139/b92-098 ◽

1992 ◽

Vol 70 (4) ◽

pp. 772-778 ◽

Cited By ~ 7

Author(s):

E. R. Littley ◽

J. E. Rahe

Keyword(s):

Potato Dextrose Agar ◽

White Rot ◽

Acellular Matrix ◽

Sclerotium Cepivorum ◽

Dry Conditions ◽

Axenic Conditions ◽

Survival Differences ◽

Moisture Conditions ◽

Scanning Electron

Sclerotial ontogeny, maturation, and aging in Sclerotium cepivorum are described using light and scanning electron microscopy. On potato dextrose agar, the mycelium spread, branching irregularly. Six days after inoculation sclerotial initials appeared, formed by hyphae branching and looping. From 6 to 8 days, the number and size of initials increased, and mucilagenous material appeared. By day 9, hyphal bundles formed in the mycelium. Between 9 and 11 days, spherical forms developed and the sclerotia grew. By day 12, an acellular matrix appeared, and to day 18 this matrix progressively obscured the surface hyphae and became black. A layer of ovoid rind cells developed at the surface. To examine the reduced survival of laboratory-produced compared with field-collected sclerotia, sclerotia from a variety of sources and conditions were compared. In general, the rind of sclerotia aged in dry conditions had a broken, irregular appearance versus fresh sclerotia or sclerotia aged under moist, axenic conditions. Sclerotia aged dry developed 1 to 4 layers of rind cells, while sclerotia kept moist developed only 1 or 2 layers. The structural and survival differences between laboratory-produced and natural sclerotia are attributable to differences in the moisture conditions under which they matured and aged. Key words: Sclerotium cepivorum, white rot, morphogenesis, sclerotia.

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Mycoparasitism of selected sclerotia-forming fungi by Sporidesmium sclerotivorum

Canadian Journal of Botany ◽

10.1139/b98-019 ◽

1998 ◽

Vol 76 (3) ◽

pp. 460-466 ◽

Cited By ~ 2

Author(s):

Sue Mischke

Keyword(s):

Castor Bean ◽

Ricinus Communis ◽

Gray Mold ◽

Causal Agent ◽

Sclerotium Cepivorum ◽

Ricinus Communis L ◽

The Family ◽

Host Parasite

Sporidesmium sclerotivorum Uecker, Ayers, & Adams is mycoparasite of sclerotia with potential for biocontrol. Sclerotia of fungi in the sclerotial lineage of the Sclerotiniaceae, including species of Sclerotinia, Botrytis, Amphobotrys, and Monilinia, stimulated germination of macroconidia of Sp. sclerotivorum. The mycoparasite readily colonized sclerotia of Sclerotinia spp. and Amphobotrys ricini (Buchwald) Hennebert both in soil and in vitro. Sclerotia of Botrytis spp. were parasitized only occasionally, and some Sclerotiniaceae were not parasitized. The limits on the ability of Sp. sclerotivorum to parasitize sclerotia support its classification as fastidious. Not even the first step in mycoparasitism, germination of Sp. sclerotivorum macroconidia, was triggered by sclerotia of fungi outside of the family. Amphobotrys ricini, the causal agent of gray mold of castor bean (Ricinus communis L.), is a newly recognized host of Sp. sclerotivorum, and sclerotia of this pathogen were destructively colonized by the mycoparasite.Key words: Amphobotrys ricini, biocontrol, host-parasite interaction, Sclerotiniaceae, Sclerotium cepivorum, signal.

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SCREENING WORLD ONION GERMPLASM COLLECTION FOR RESISTANCE TO WHITE ROT

Canadian Journal of Plant Science ◽

10.4141/cjps78-120 ◽

1978 ◽

Vol 58 (3) ◽

pp. 819-822 ◽

Cited By ~ 13

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.

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Compatibility of the biocontrol agent Trichoderma harzianum C52 with selected fungicides

New Zealand Plant Protection ◽

10.30843/nzpp.2001.54.3780 ◽

2001 ◽

Vol 54 ◽

pp. 84-88 ◽

Cited By ~ 13

Author(s):

K.L. McLean ◽

J. Hunt ◽

A. Stewart

Keyword(s):

Disease Management ◽

Trichoderma Harzianum ◽

Seed Treatment ◽

Biocontrol Agent ◽

In Vitro Assay ◽

Management Programme ◽

White Rot ◽

Vitro Assay ◽

Sclerotium Cepivorum

Trichoderma harzianum C52 is an effective biocontrol agent of the onion white rot pathogen Sclerotium cepivorum For this biocontrol agent to be integrated into an existing disease management programme it must be compatible with the fungicides commonly used on onions The sensitivity of T harzianum spores to the field rate of eight fungicides commonly applied to onions was determined in an in vitro assay Results indicate that T harzianum was least sensitive to procymidone and captan and most sensitive to mancozeb tebuconazole and thiram A glasshouse pot trial confirmed that T harzianum was sensitive to mancozeb but tolerant of captan This research indicates that in furrow applications of T harzianum would be compatible with a captan and/or benomyl seed treatment for control of other seedling diseases

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Control of white rot of garlic by antagonistic fungi under controlled environmental conditions

Canadian Journal of Microbiology ◽

10.1139/m84-138 ◽

1984 ◽

Vol 30 (7) ◽

pp. 884-889 ◽

Cited By ~ 21

Author(s):

Vetúria L. de Oliveira ◽

Margarida de M. Bellei ◽

Arnaldo Chaer Borges

Keyword(s):

Cell Wall ◽

Trichoderma Harzianum ◽

Environmental Conditions ◽

Paecilomyces Lilacinus ◽

White Rot ◽

Infested Soil ◽

Conidial Suspension ◽

Sclerotium Cepivorum ◽

Penicillium Sp

Several fungi were isolated from soil samples collected in areas with a high incidence of white rot disease of garlic at Amarantina county, Minas Gerais, Brazil. After the screening in vitro for antagonists to Sclerotium cepivorum, three fungi were found to be highly inhibitory to the pathogen. These fungi were identified as Trichoderma harzianum Rifai, Paecilomyces lilacinus (Thom.) Samson, and a Penicillium sp. The three antagonists produced in vitro nonvolatile antibiotics towards Sc. cepivorum. These substances were thermolabile (120 °C, 15 min) and significantly inhibited the growth of Sc. cepivorum. Interactions between the pathogen and each antagonist, studied by a dual slide-mount technique, showed that Pa. lilacinus and Penicillium sp. caused an inhibition halo to Sc. cepivorum although hyphal contact never occurred. Trichoderma harzianum showed inhibitory activity at a distance, and after contact with Sc. cepivorum, caused hyphal cytoplasm disintegration and cell wall collapse. This detrimental effect occurred either after direct penetration of the cell wall or after the formation of "coilings." The efficacy of the three antagonists in the biocontrol of white rot was tested under controlled environmental conditions in a nonsterilized, artificially infested soil (1 sclerotia per gram of soil). Trichoderma harzianum VL1 applied as a conidial suspension (106 conidia/mL) during the transplanting period significantly reduced the severity of white rot and increased the number of healthy plants when compared with the untreated control. Trichoderma harzianum gave significantly better protection to the plants than Coniothyrium minitans, a known biocontrol agent of sclerotia-forming fungi. Paecilomyces lilacinus, Penicillium sp., and the mixture of the three antagonists gave no protection against the disease.

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