Plant diseases caused by Bacteria 1. Spots and Blights Wild fireSpotSpeck 4. Vascular wilts wiltFire blightBlack rot 2. Soft rots3. Galls 6. Canker and Gummosis Canker and Gummosis Canker 5. Scabs

1.Bacterial spots and blights a- Wildfire of tobacco Disease name: Wildfire Plant: Tobacco (Nicotiana tabacum L.) Pathogen: Pseudomonas syringae

Symptoms : Round spots: brown in centers and whitish yellow halos Adjacent spots coalesce → large dead area on the leaf

b- Bacterial spot of tomato and pepper Disease name: Bacterial spot Plant: Tomato, Pepper Pathogen: Xanthomonas campestris

Symptoms: Tomato On unripe fruits: small water soaked, slightly raised spots. spots sometimes have greenish-white halos → dark brown with scabby surface.

Pepper On unripe fruits: small water soaked, slightly raised spots. spots sometimes have greenish-white halos → dark brown with scabby surface.

c- Bacterial speck of tomato Disease name: Bacterial Speck Plant: Tomato Pathogen: Pseudomonas syringae

Symptoms: Lesions are similar to bacterial spot but smaller

2.Bacterial vascular wilts a- Bacterial wilt of cucurbits Disease name: Bacterial wilt Plant: Cucurbitaceae Pathogen: Erwinia tracheiphila

Symptoms: Drooping and wilting of infected leaves, which shrivel and dry up. Infected stems become soft and pale then shrivel (ذبول), hard and dry.

b- Fire blight of Pear and Apple Disease name: Fire blight Plant: Pear, Apple Pathogen: Erwinia amylovora

Symptoms: Apple Bark turns brownish black and soft → shrinks and hardens Brown, black blotches along midrib and between veins then curl and shrivel. Bacterial exudates (ooze) from apple fruit and stem.

Pear Brown, blak blotches along midrib and between veins then curl and shrivel. Immature fruit become water soaked, then shrivel, turn black.

c- Black rot of crucifers Disease name: Black rot Plant: Crucifers Pathogen: Xanthomonas campestris

V-shaped chlorotic blotches at the margins of the leaves → chlorosis progress toward the midrib → affected area turn brown and dry. Cabbage and cauliflower heads are discolored. Symptoms:

3.Bacterial soft rots Bacterial soft rots of vegetables Disease name: Bacterial soft rots Plant: Vegetables ( potato, carrot,..), annual ornamentals (iris), succulent stems, stalk or leaves (cabbage, lettuce,..). Pathogen: Erwinia carotovora

Symptoms: Affected area becomes soft and mushy, the surface becomes discolored and depressed. Cracks develops the slimy mass exudates to the surface and turn brown. Cruciferous plants and onions give off repulsive odor.

A whole fruit or tuber may be converted into a soft, watery, decay mass within 3-5 days.

4.Bacterial galls Disease name: Crown gall Plant: Woody and herbaceous plants (> 60 families), mostly on pome and stone fruit trees, brambles and grapes. Pathogen: Agrobacterium tumefaciens

Symptoms: Small, round, whitish soft overgrowth on the stem and roots (mainly near the soil line) → the tumor enlarge and become brown (death and decay of peripheral cells). Some tumors are spongy while others become woody and hard.

5.Bacterial canker and gummosis a- Bacterial canker and gummosis of stone fruit trees Disease name: Bacterial canker and gummosis Plant: Stone fruit trees (apricot, pear,olive,…) Pathogen: Pseudomonas syringae

Bacterial canker: Formation of cankers girdled the trunk or branches. Within few week, the branch or entire tree above the canker die. Leaves show curling and turn yellow. Symptoms:

Gummosis: gum exudation

b- Citrus canker Disease name: Citrus canker Plant: Citrus Pathogen: Xanthomonas axonopodis

Symptoms: Similar lesions are on young leaves, twigs and fruits. Small round light green spots (lesions) → they rupture and appear corky with brown sunken centers and yellow halo. Premature fruits drop.

6.Bacterial scabs Common scab of potato Disease name: Common scab Plant: Potato, root crops (beets, radish,..) Pathogen: Streptomyces scabies

Symptoms: Small brownish raised spots → enlarge, coalesce and become corky. The lesions extend 3-4 mm deep in tuber

Plant diseases caused by parasitic higher plants Dodderr Cuscuta spp. Witchweed Striga spp.

1.Dodder Cuscuta spp. Plant: alfalfa, onion, sugar beets, some ornamentals and potato. Parasite: Cuscuta spp.(dodder)

Symptoms: Orange or yellow strands around the stem and the other aboveground parts of the plant. The parasite enter their haustoria directly to the phloem of the host. During late spring and in summer, dodder produces clusters of white, pink or yellowish flowers. Infected host produce poor yield and may be killed by parasite.

2.Witchweed Striga spp. Plant: economic plants (corn, sugarcane, rice, cowpeas, tobacco, small grains,..) Parasite: Striga spp.

Symptoms: The parasitic roots are attached to the host ones by its root exudates → the root haustorium penetrates the host roots → the haustorium reach the vessels of the host roots, from which it absorb water and nutrients → infected host became stunted and chlorotic → wilt and die