Produce decay identification – “Black mold rot” in stored produce is classically caused by which fungus?

Introduction / Context:
Different moulds cause distinct visual rots, and correct identification aids in root-cause analysis. Black mold rot is a well-known postharvest issue in onions, grapes, and other commodities.

Given Data / Assumptions:

• We are matching the descriptive term “black mold rot” to a causal agent.
• Options include several common postharvest mould genera.

Concept / Approach:
Aspergillus niger produces abundant black conidia, giving a characteristic black mold appearance on infected tissues. This presentation distinguishes it from yellow-green A. flavus, pink molds (Trichothecium), or fast-growing white-gray Rhizopus.

Step-by-Step Solution:
Link visual descriptor “black” with conidial color → A. niger forms black conidial heads. Check commodity associations → onions and certain fruits frequently display A. niger black mold. Therefore, select Aspergillus niger.

Verification / Alternative check:
Postharvest pathology references label black mold of onion and grapes as typically caused by A. niger complex.

Why Other Options Are Wrong:
A. flavus produces yellow-green colonies; Trichothecium roseum produces pinkish colonies; Trichoderma is usually green; Rhizopus causes soft rot with black sporangia but the named “black mold rot” classically points to A. niger.

Common Pitfalls:
Confusing Rhizopus black sporangia with the dense black conidial growth of A. niger; laboratory confirmation may be needed.

Final Answer:
Aspergillus niger.