Pyrenophora tritici-repentis

Pyrenophora tritici-repentis is a necrotrophic fungus that is the causal agent of Tan spot, a disease of wheat. It is a member of the Ascomycota phylum in the kingdom Fungi. This fungus is known for its ability to produce a host-selective toxin (HST) that can cause necrosis or chlorosis in sensitive wheat cultivars.

Taxonomy

Pyrenophora tritici-repentis is a species in the genus Pyrenophora, which is part of the family Pleosporaceae. The genus name 'Pyrenophora' is derived from the Greek words 'pyren', meaning 'kernel', and 'phora', meaning 'bearer'. The species name 'tritici-repentis' refers to its host, wheat (Triticum), and the creeping or 'repent' growth habit of the fungus.

Life Cycle

The life cycle of Pyrenophora tritici-repentis begins with the germination of ascospores or conidia, which are the primary inoculum. These spores land on the surface of the wheat leaf and germinate, producing a germ tube that penetrates the leaf surface. The fungus then grows intercellularly, producing a mycelium that spreads throughout the leaf tissue. The fungus produces HSTs that cause necrosis or chlorosis in sensitive wheat cultivars. The fungus then produces conidiophores that bear conidia, which are dispersed by wind or rain splash to other wheat plants, completing the life cycle.

Disease Management

Management of Tan spot caused by Pyrenophora tritici-repentis involves a combination of cultural practices, genetic resistance, and chemical control. Cultural practices include crop rotation, residue management, and planting disease-free seed. Genetic resistance involves the use of wheat cultivars that are resistant to the HSTs produced by the fungus. Chemical control involves the use of fungicides that are effective against Pyrenophora tritici-repentis.

See Also

• Tan spot
• Ascomycota
• Pleosporaceae
• Fungicide

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