Biotic Diseases (cont.)

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Biotic Diseases (cont.)

• Fungal Diseases (cont.)

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Rhizopus

• The Mycelium consists of branched non septated
  hyphae, which grow creeping upon the substratum,
  called Stolon.
• Each stolon sends branched rhizoids to the
  substratum for absorption of the necessary food
  material.
• Opposite to rhizoids , sporangiophores arise ,
  each terminating with numerous spores and sterile
  portion known as columella.

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Disease

• Rhizopus soft rot
• Symptoms
• The color of the infected tissue turns from
  purple to brown, and a pronounced fermentive odor
  is produced. The odors from affected sweet
  potatoes attract fruit flies, which reproduce in
  the decaying tissue and become abundant in the
  storage area.

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Aspergillus

• The mycelium is branched and septated.
• Conidiophore is unbranched and non
  septated terminates with swollen heads , each of
  which carries radiating stregmata.
• Chain of conidia arranged in basipetal
  succession

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A. fumigatus
A. clavatus
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Disease

• Aspergillus ear rot
• Symbtoms
• Aspergillus niger appears as a black mold on
  infected kernels. A. flavus is a greenish-yellow
  mold growing on damaged kernels. A. glaucus is a
  greenish mold

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Penicillium

• Species of Penicillium are recognized by their
  dense brush-like spore-bearing structures.
• The conidiophores are simple or branched and are
  terminated by clusters of flask-shaped phialides.
  The spores (conidia) are produced in dry chains
  from the tips of the phialides, with the youngest
  spore at the base of the chain, and are nearly
  always green.
• Branching is an important feature for identifying
  Penicillium species.

conidia
phialides
Conidiophore
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• Disease
• Penicillium stem rot .
• Symbtoms
• Infection appears initially as water-soaked,
  translucent areas at the nodes, especially nodes
  that have been pruned. Within a day or so, this
  becomes a pale-brown canker with a blue-gray to
  blue-green fungal growth on the surface giving
  off a cloud of spores

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Alternaria

• The mycellium consists of branched and
  septated hyphae.
• Conidiophores are mostly unbranched and
  septated.
• Conidia develop at the tips of
  conidiophores.
• Conidia with transverse and longtudinal
  septa, mostly elongate at the tip, muriform in
  the lower portion , borne usually in simple
  chains.

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Disease
Early Blight disease Symptoms The disease
appear as , dark, round depressions on the peel
causing dark necrotic concentric lesions
. Initial infestation is by wind-borne conidia
that penetrate through superficial wounds in the
epidermis.
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Curvularia

• Composed of branched and septated mycelium.
• Conidiophores are unbranched and septated .
• Conidia may be obclavate or cylindrical ,
  usually curved , carried singly on the
  conidiophores.
• Conidia with 3 or 4 septa , the central cell
  being larger than the terminal cells.

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Disease

• Curvularia blight
• Symptoms
• Small yellow-brown spots on leaves expand to
  oblong lesions. Center of lesions change to brown
  and margins remain yellow. Lesions are more
  common on leaf margins.

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Fusarium

• 1- Mycelium consists of branched septated
  hyphae .
• 2- Fusarium reproduces asexually by means of 3
  kinds of asexual spores
• a) Macroconidia long , multicellular and
  crescent-shaped, both ends of macroconidia are
  pointed , cells from which Macroconidia develops
  are called phialides.
• b)Microconidia are small , usually unicellular
  , spherical or oval bodies.
• c) Chlamydospores are round or oval thick
  walled , terminal or intercalary vells of the old
  hyphae

Macroconidia
Microconidia
Chlamydospores
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Macroconidia
Microconidia
Chlamydospoes
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Disease

• Fusarium root rot
• Symptoms
• The disease initially appears as red to
  reddish-brown lesions on stems and primary root
  2-3 weeks after planting.Affected areas may merge
  and enlarge with age, turn necrotic, and
  gradually extend up from the soil surface.
  Primary and secondary roots are killed in severe
  cases. If moisture is sufficient, lateral roots
  may develop above the initial site of infection,
  which helps plants survive. Infected plants are
  rarely killed and above ground symptoms in the
  field include stunting and yellowing of leaves

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Reddish-Brown Lesions
Gradually Extend
Merge and Enlarge
Lateral Roots May Develop
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Cladosporium

• It is found both indoors and outdoors.
  Colonies range from a dark green to black color.
• They are relatively slow-growing.
• The dark spores are normally one to two
  celled and occur in long, branching chains that
  arise from a dark conidiophore.
• The youngest spores are those found at the
  top of the chain

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Disease

• Cladosporium ear rot Cladosporium herbarum and
  other species often infect kernels damaged by
  insects, hail, or frost.
• Symptoms
• 1-This fungus appears gray to black or very dark
  green.
• 2- can have a powdery appearance.
• 3-It also causes black streaks in the kernels.
• This disease can be fairly common but usually
  does not cause extensive damage to the ears.

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