Fusarium head blight (FHB), caused by Gibberella zeae, is a devastating disease of wheat. A strain of Clonostachys rosea, ACM941 (American Type Culture Collection ATCC 74447), was evaluated for antibiosis against G. zeae in vitro and for control of FHB under greenhouse and field conditions in comparison to the registered fungicide Folicur (tebuconazole). Strain ACM941 reduced mycelial growth of the pathogen by 52.6% in dual-culture after 6 days and completely suppressed spore germination for 6 h when cocultured with a macroconidial suspension of G. zeae. Strain ACM941 reduced G. zeae perithecial production by more than 99% in a leaf disk assay, 60%-77% on infected corn kernels, and 32%-57% on spikelet debris in the field. These effects were significant (P < 0.05) and not statistically different from those produced by tebuconazole. When strain ACM941 was sprayed onto wheat heads 2 days prior to inoculation with G. zeae, it significantly reduced infected spikelets (IS) by 64% and Fusarium-damaged kernels (FDK) by 65% in greenhouse experiments. Under simulated disease epidemic conditions during 2005-2007, strain ACM941 reduced the FHB index by 58%, IS by 46%, FDK by 49%, and deoxynivalenol (DON) in kernels by 21%. These effects were significant but lesser in magnitude than those achieved by tebuconazole, which reduced FHB index by 97%, IS by 82%, FDK by 73%, and DON by 62%. Results from this research suggest that strain ACM941 of C. rosea is a promising biocontrol agent against G. zeae and may be used as a control measure in an integrated FHB management program. Key words: biological control, Gibberella zeae, fusarium head blight, Clonostachys rosea, wheat. Xue et al.: fusarium head blight / biological control / Clonostachys rosea 179 Résumé : La fusariose de l'épi (FHB), causée par Gibberella zeae, est une maladie dévastatrice qui s'attaque au blé. La souche ACM941 (ATCC 74447) de Clonostachys rosea a été évaluée, in vitro, sur le plan de l'antibiose pour lutter contre G. zeae et, en serre et au champ, pour lutter contre la FHB afin d'en comparer les effets à ceux du traitement fongicide homologué Folicur (tébuconazole). Au bout de six jours, lors de tests en culture duale, la souche ACM941 a réduit de 52,6 % la croissance mycélienne de l'agent pathogène et en a entièrement inhibé la germination des spores pendant six heures lorsqu'on l'a fait croître en présence d'une suspension macroconidiale de G. zeae. Lors d'un test biologique sur disque foliaire, la souche ACM941 a réduit la production périthéciale de plus de 99 %, de 60 % à 77 % lors d'un test sur des grains de maïs et de 32 % à 57 %, au champ, lors d'un test sur des débris d'épillets. Ces résultats étaient significatifs (P < 0,05) et semblables statistiquement à ceux obtenus avec le tébuconazole. Lorsque, au cours d'expériences menées en serres, la souche ACM941 a été pulvérisée sur des épis de blé deux jours avant de les inoculer avec G. zeae, les taux d'infection des épillets (IE) et les dommages subits par les grains affectés par Fusarium (DGF) ont été s...

No abstract

No abstract

Hiemalis begonias Fotsch (Begonia × hiemalis), a member of the family Begoniaceae, is a commercially important potted flowering plant in Europe and North America. In the spring of 2010, stunted growth and dull green leaves of H. begonias were observed in a commercial greenhouse in southern Ontario, Canada. Symptoms began with dull green foliage, followed by wilted leaves, then the stem base became water soaked with vascular discoloration, and finally, large macroconidial masses of a fungus developed on the collapsed stems and veins. A fungus was consistently isolated from the leaves, stems, and roots of symptomatic plants. Single conidia were isolated from sporodochia and cultured on potato dextrose agar (PDA) and oatmeal agar (OA) for 7 days. Isolates exhibited strong pungent odors on PDA and OA and a brownish orange colony on OA and a light orange colony on PDA. Masses of light orange and hemispherical-shaped conidia and stromata formed on OA. Conidiophores formed from aerial mycelium producing ellipsoidal microconidia without septation. Sporodochia formed on agar surface producing three-septate, slightly curved macroconidia. The cultural and conidial characteristics of the isolates were similar to those of Fusarium foetens Schroers (4). Partial translation elongation factor 1-α (TEF) gene was amplified and sequenced with primers ef1 and ef2. A comparison of a partial sequence has been deposited in GenBank (Accession No. HM748968) and showed a 100% match with F. foetens (2). Inoculations with F. foetens isolates were performed by injecting a 100-μl suspension of 1 × 106 conidia/ml into stems of five healthy plants near the ground or soaking the soil of five healthy 6-week-old H. begonias cv. Golden Edith with 50 ml of suspension. Control plants were similarly injected with sterile water or sown in sterile soil. After 4 weeks, all inoculated plants developed dark, wilting leaves and collapsed stems and veins similar to those observed in the commercial greenhouse. F. foetens was reisolated from diseased plants, and identification was reconfirmed by conidial characteristics and TEF 1-α sequence. Control plants were healthy and symptom free. F. foetens has recently been described in association with a new disease of H. begonias in Europe (3) and the United States (1). F. foetens can cause major economic losses to farmers and marketers of H. begonias in Europe and the United States. To our knowledge, this is the first report of F. foetens causing wilt disease of H. begonias in Canada. References: (1) W.-H. Elmer et al. Plant Dis. 88:1287, 2004. (2) D.-M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (3) R. Schrage. Phytomed. Ges. 33:68, 2003. (4) H.-J. Schroers et al. Mycologia 96:393, 2004.

No abstract