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Black Rot (Aspergillus niger)

Image of Black Rot (Aspergillus niger)

Scientific classification:

Kingdom: Fungi
 Subkingdom: Dikarya
  Phylum: Ascomycota
   Subphylum: Pezizomycotina
    Class: Eurotiomycetes
     Subclass: Eurotiomycetidae
      Order: Eurotiales
       Family: Trichocomaceae
        Genus: Aspergillus
         Species: Aspergillus niger

Aspergillus niger is a filamentous fungus that has many applications in biotechnology.  A. niger is considered to be one of the most essential of those microorganisms. This fungus is responsible for Aspergillus crown, pod and seed rot of peanut and black mould of onion.

This disease can be of great economic importance in warm conditions. Seedlings and young plants are more susceptible to the pathogen. Diseased areas of the effected plant are covered in dark fungal growth. Infection of seedlings commonly occurs soon after germination.

The disease progresses rapidly, and most affected plants will die within 30 days of planting. Infected onion bulbs have a black discolouration at the neck, shallow lesions on the outer scales, streaks of black mycelium and conidia beneath the outer scales and a black discolouration in bruised areas. The entire surface of the bulb may turn black, in which case, the onion will shrivel and secondary bacteria may cause a soft rot of the bulb.

Control:

Fungicide seed treatments may be effective when used under conditions that promote rapid germination and emergence to prevent damping off. Post-harvest black rot can be controlled if produce is stored and transported below 15°C or under very low humidity.