Puccinia graminis tritici

Stages on the primary host; Wheat

1. Uredospores (on wheat)

1. Uredospores are borne in groups under the epidermis, called uredosorus.
2. The uredosorus develops on wheat plant from the dikaryotic mycelium produced by germination of aeciospore.
3. The uredospores appear in the form of reddish-brown pustules.
4. The uredospores are stalked, oval, unicellular, brown, thick walled with 4-round equatorial germ pores.
5. The spore wall is thick with the echinulate outer layer.

Uredosorus showing stalked unicelled, binucleate uredospores

2. Teliospores (on wheat)

1. Teleutosorus develops exclusively by the infection of uredospore.
2. The teleutosori look black raised streak on leaf sheath and also on stem.
3. The teleutospores are stalked, spindle-shaped, thick and smooth-walled with round or pointed apex, 2-celled and slightly constricted at the septum.
4. Spores are chestnut brown in color.
5. Each cell is dikaryotic (n + n) having one germ pore.The germ pore is at the top of the apical cell and it is below the septum in the lower cell.

Teliosorus showing stalked bicelled, binucleate teliospores

Stages on the primary host; Barberry

3. Pycnidiospores (on barberry)

1. Pycnidium is developed under the upper epidermis in the form of a yellowish flask-shaped structure.
2. The pycnidium has small sterile mycelium at the neck, called periphyses, which intermingle with much larger thin-walled simple and branched receptive or flexuous hyphae.
3. The bottom of the inner side of pycnidium is lined by many uninucleate tapering cells, the  spermatiophores, which develop many small oval to spherical uninucleate cells, called pycniospores (spermatia).
4. The pycnidiospore may be of + or – type.
5. The mature pycnidium (+ and – type) secretes nectar drops during release of mature pycnidiospores which get intermixed.
6. The insects get attracted by nectar and help in the transfer of pycnidiospores to the flexuous hyphae of opposite mating type.
7. The wall at the point of contact dissolves and the nucleus of the pycnidiospore passes to the flexuous hyphae, thus a dikaryotic condition is established. This process is known as spermatisation.

Pycnidial cup showing the pycnidiospores

4. Aeciospores (on barberry)

1. The young aecium is borne inside the tissue below the lower epidermis, but with maturity it pushes and ruptures the epidermis, thereby spores are exposed.
2. liThe aecium is an inverted cup-shaped structure with outer margin composed of short cells, called peridium.
3. The stalk cell after becomes dikaryotized, divided mitotically into a chain of alternately arranged large and small cells.
4. The large cells form the aeciospores (n + n) and the small one becomes sterile, called the disjunctor cell.The disjunctor cell helps in spore dispersal.
5. The aeciospores are unicellular, binucleate (n + n), thin-walled and orange in colour.
6. The young aeciospores are polyhedral in shape, but become globose with maturity.

Aecial cup showing chain of unicelled, binucleate aeciospores

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Content first created on 01-09-2023
last updated on 01-09-2023