Abstract:

Pyrenophora tritici-repentis (asexual stage: Drechslera tritici-repentis) is an important disease agent that causes tan spot disease in wheat all over the world. Pyrenophora tritici-repentis is found in the class Dothideomycetes, which is the largest and most diverse class of Ascomycota fungi. The fungus can reproduce asexually with conidia and sexually with ascospores. Pyrenophora tritici-repentis has a complex race structure. Race identification was based on the production of three host-specific toxins (ToxA, ToxB, ToxC) produced by the pathogen. Recently these are named Necrotrophic Effectors (NE). The race of each effector-producing pathogen is differentiated according to the toxin or combination of toxins it produces. If it does not produce toxins, it is considered an avirulent race. These produced toxins determine the symptoms that will be caused by the pathogen. For the agent to cause disease, the host plant must be susceptible to NEs produced by the race in question. Race identification is made with a differential set and eight races of the pathogen are defined according to this differential set. The differential set consists of six wheat lines and varieties, but only the Glenlea variety and lines 6B365 and 6B662 can effectively separate existing races. This disease, which is also present in Turkey, can affect the leaves as well as the spikes and grains. Symptoms may be necrosis, chlorosis, or both. Brown spots appear first in all symptom cases. In necrosis, the brown spots elongate and enlarge, resulting in lens- or diamond-shaped lesions. These lesions are bordered by yellow halos. In chlorosis, yellow areas are formed that rapidly surround and develop the lesions on the leaf blade. As the lesion grows, it merges with other lesions, forming large and irregularly shaped dead tissues. Symptoms first appear on the older lower leaves and spread to the upper leaves as the disease progresses. The disease can reduce the yield by 50% in susceptible varieties. In order to be able to fight the pathogen effectively, an integrated control using various control methods should be applied. In this review, information about tan spot disease and its control is given.

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