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RESULTS

(13)

DISEASE: Bacterial leaf spot (Head rot)

HOST: Lettuce

Leaf with black, greasy spots that tend to be vein delimited. Lesions begin as small, angular, water-soaked lesions that coalesce, resulting in large necrotic areas.

DISEASE: Corky root

HOST: Lettuce

Corky root causes a reduction in size of lettuce heads and root systems; susceptible cultivar (right) and resistant cultivar (left).

DISEASE: Corky root

HOST: Lettuce

Close-up of root with malformed, corky appearance and longitudinal ridges of brown tissues.

DISEASE: Corky root

HOST: Lettuce

Initial symptoms of disease are yellow lesions on taproot and main laterals. Greenish brown bands occur around roots. Root pith may become brown and hollow.

DISEASE: Corky root

HOST: Lettuce

Differences in corky root symptoms between susceptible cultivar (right) and resistant cultivar (left).

DISEASE: Head rot (Jelly rot)

HOST: Lettuce

Sliced head of lettuce. Typical symptoms are a translucent appearance and browning or jelly rot of the stalk (crown).

DISEASE: Head rot (Jelly rot)

HOST: Lettuce

Advanced stage of lettuce stalk rot (crown).

DISEASE: Head rot (Jelly rot)

HOST: Lettuce

Head rot of lettuce first appears as rapid wilt of outer wrapper leaves. Wilt is caused by collapse of vascular tissues, which develop a pinkish to brown discoloration.

DISEASE: Marginal leaf blight

HOST: Lettuce

Marginal leaf blight first appears as slimy wilting of leaf margins. Small, reddish lesions may be seen on leaf blades. Infected tissues turn brown to black in time.