Bitterness:

Band of dark brown necrosis around the crown and horizontal brown canker-like lesions mostly on the crown and upper roots
Small pits subsequently developed beneath the lesions, that enlarged into sunken brown crater lines with a white, flocculent mycelium produced under high humidity

Carrots can develop off-flavours or bitterness in cool storage. The cause of these off-flavours is the production of compounds in carrots called isocoumarins. Isocoumarins develop when carrots are exposed to ethylene.
Ethylene is a gas produced naturally by many fruits and vegetables, such as apples, bananas and tomatoes during ripening.
Carrots can be stored in sealed plastic bags in domestic refrigerators containing ethylene producing fruit.

Phenolic browning :

Phenolic browning (or surface browning) is seen as a browning or discoloration of the surface of carrot.
It can develop when carrots are washed and stored in cool rooms for long periods before packing.
Abrasion caused by mechanical washing often removes the epidermal layer (outer skin), exposing the carrot tissue to oxidation of phenolic compounds, which turn brown, or black in severe cases.
Phenolic browning can be confused with ‘5 o’clock shadow’ or boron deficiency of carrots. Phenolic browning can be confused with ‘5 o’clock shadow’ or boron deficiency of carrots.
The latter is seen as many small brown spots under the skin, causing the root to look dull.

Identification of pathogen:

Mode of spread and survival:

Soil - source of primary inoculum
Survive in decaying refuse and enter the root principally through cultivation wounds, harvest bruises, freezing injury, and insect openings
Flies- Hylemus cillicrura , H. brassicae carry the bacteria in their intestinal tracts


Dark brown necrosis		Canker-like lesions