Diseases

Tobacco Alternaria Leaf Spot

Nicotiana tabacum L.

A fungal disease of tobacco, known as brown spot, caused by the fungi Alternaria alternata and A. longipes. It is characterized by the appearance of brown spots with concentric rings and a yellow halo on the leaves.

In the reference 5 varieties crop Tobacco, where this is mentioned in the description.

The pathogens of the disease are facultative, capable of persisting in the soil on crop residues. The disease begins on the lower, physiologically more mature leaves, gradually spreading throughout the entire plant. Primary symptoms appear as small, water-soaked spots that reach 1–3 cm in diameter as they grow.

Mature spots are distinguished by the presence of distinct concentric rings that create a target effect, surrounded by a chlorotic halo. In high humidity, the affected areas coalesce, leading to extensive leaf necrosis, which renders the raw material unusable. The pathogen remains active even after harvest, causing barn rot during the curing process.

Breeding varieties for resistance to Alternaria leaf spot is difficult due to the opportunistic nature of the pathogen and its wide host range. There is no data in scientific literature on specific resistance genes; therefore, the assessment of varietal resistance is conducted primarily through expert evaluation using scoring scales based on field trials.

General information about the subject — on the page Alternaria blight.

Sources8

Varieties of Tobacco mentioned in the description

Selection based on the description text, not on official evaluation: these data are absent from registers. For specific variety details, please refer to its profile.