16(12): 1003 (1882) Alternaria solani is a fungal pathogen that produces a disease in tomato and potato plants called early blight.

The pathogen produces distinctive "bullseye" patterned leaf spots and can also cause stem lesions and fruit rot on tomato and tuber blight on potato.

[4] Primary methods of controlling this disease include preventing long periods of wetness on leaf surfaces[5] and applying fungicides.

A. solani is also present in most potato production regions every year but has a significant effect on yield only when frequent wetting of foliage favors symptom development.

[9][10] On tomato, foliar symptoms of A. solani generally occur on the oldest leaves and start as small lesions that are brown to black in color.

Under favorable conditions (e.g., warm weather with short or abundant dews), significant defoliation of lower leaves may occur, leading to sunscald of the fruit.

Mature lesions are typically covered by a black, velvety mass of fungal spores that may be visible under proper light conditions.

Initial infection occurs on older leaves, with concentric dark brown spots developing mainly in the leaf center.

The disease progresses during the period of potato vegetation, and infected leaves turn yellow and either dry out or fall off the stem.

[12] Disease severity due to A. solani is highest when potato plants are injured, under stress or lack proper nutrition.

A.solani is generally considered to be a necrotrophic pathogen, i.e. it kills the host tissue using cell wall degrading enzymes and toxins and feeds on the dead plant cell material [14] The life cycle starts with the fungus overwintering in crop residues or wild members of the family Solanaceae, such as black nightshade.

After penetration, lesions may form within 2–3 days or the infection can remain dormant awaiting proper conditions [15.5 °C (59.9 °F) and extended periods of wetness].

Some of the fungicides on the market are (azoxystrobin), pyraclostrobin, Bacillus subtilis, chlorothalonil, copper products, hydrogen dioxide (Hydroperoxyl), mancozeb, potassium bicarbonate, and ziram.

However, decreased fungicide sensitivity has been observed in A. solanidue to a F129L (Phenylalanine (F) changed to Leucine at position 129) amino acid substitution.