Biology

The Aspergillus spp. have biological characteristics comparable to those of many other rotting agents on grape berries, and in particular Penicillium spp. . We advise you to consult the dedicated sheet. You should already know that they often live as saprophytes on the vine and in its environment, becoming opportunistic pathogens when the physiological state of the berries is modified (presence of wounds, advanced maturity ... ).

A. niger is cosmopolitan, it grows on organic matter and on various substrates. It has been found in soil, in compost and on decaying plant material. It usually prefers dry, warm soils. it grows very well at temperatures between 20-40 ° C. Although preferring dry environments, this species can however thrive very well in an environment where the relative humidity is 90-100%. It also supports very low pH, down to pH 2.0.

Description of these mushrooms

• The long biseriate conidiphores of A niger (1.5 to 3 mm) start from a basal cell located on the hypha (figures 1 to 3); their wall is smooth, hyaline and darker at the apex which, when dilated, forms a globular vesicle (30-75µm in diameter). It is on this vesicle, typical of the genus Aspergillus , that the phyalids are located, which cover its entire (radial) surface (figure 4). With age, the conidial heads split into columns.
• The phyalids , in the form of bottles (7-20 x 3-5 µm) (figure 4), are attached to the vesicle either directly or via an intermediate cell: the metule, a sterile cell formed by the vesicle.
• The conidia are spherical and slightly flattened, brown to black, rough (warty) and whose diameter generally oscillates between 4 and 5 µm. They are arranged in basipetal radial chains.
• Appearance of colonies on malt-agar medium : those  of A. niger have a relatively rapid growth. The septate and hyaline hyphae of Aspergillus initially give the colonies a cottony white appearance; these darken and become black or even powdery with the production of black spores (figure 5). The back of the colony, for its part, takes on a white-yellow color.