Guignardia bidwellii

Genus/species: Guignardia bidwellii (teleomorph) Phyllosticta ampelicida (anamorph), black grape rot

Classification: Ascomycete

Morphology:

  • Cell: On the periphery of cultures the mycelium is composed of varicose hyphae, 2-6 μm diameter.
  • Malt agar: Pychnidia are whitish exudate which appears around the ostiole and forms a cirrhus some minutes after the deposit of a firm of water.
  • WL: unknown
  • Spore: Conidiogenous cells conical to cylindrical. Conidia non-septate, hyaline, broadly ovoid, ellipsoidal or almost globose, somewhat clavate when young and slightly indented, 5-12 x 4-7 µm, surrounded by a mucilaginous sheath and with an apical hyaline appendage as long as the conidium. Ascospores are hyaline, non-septate, ovoid to ellipsoid (12-17 x 6-7.5 µm), often with hyaline, mucilaginous, apical caps
  • Zygote: unknown
  • Ascus: Asci (45-65 x 9-14 µm) are fasciculate, cylindrical to clavate, short-stipitate and eight-spored. The ascus wall is thick and composed of two layers.
  • Liquid Growth: unknown

Physiological Traits:

Hyphal growth of grape isolates of Guignardia bidwelli were inhibited by GO (purified thaumatin-like protein) and CBC (chitinases).

Ecological Traits:

All young green grapevine tissue including shoots, inflorescences and berries may be infected. Ascospore inoculum has been shown to be airborned and as a result of rainfall.

Distinguishing Features:

Optimum temperature for growth and production of pycinidia in culture is 25 °C, and the optimum temperature or germination of conidia is 30 °C.

Role in wine:

Cluster infections have an effect on yield and berry quality and affected grapes are not suitable for wine production. Best to avoid processing infected grapes with black rot in wine production.

Sensitivities:

  • SO2: unknown
  • Sorbate: unknown
  • DMDC: unknown
  • pH: unknown
  • Acids: unknown
  • Ethanol: unknown
  • Anaerobiosis: unknown
  • Heat: 35ºC

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