Beschreibung:
<p>Tan spot of wheat caused by Drechslera tritici-repentis is a major leaf spot disease. The objectives of this work were to estimate the incidence of D. tritici-repentis in wheat seed using different techniques, determine the rate of seed transmission under greenhouse and field conditions, and to evaluate fungicide seed treatments for disease control. The incidence of seed infection was 22.5%; 17.5% and 11.25% on a selective medium for Cochliobolus sativus, lima bean agar and in the deep-freezing method respectively. On agar, the fungus produced black immature pseudothecia on the seeds and sometimes on the roots; the pseudothecia maturated after 30 days in darkness at 5°C. The pathogen was transmitted from seed to coleoptiles of symptomless plumules seedlings at a rate of 15.5% under greenhouse conditions, and to the plumule with tan spot symptom at a rate of 31% under field conditions. The seed treatment study indicated that a mixture of iprodione + triticonazole was the most effective treatment, reducing the rate of transmission from 31% to 8.8%. This is the first report of detection and transmission of D. tritici repentis in wheat seed in Argentina. The importance of infected seed and its epidemiological role are discussed.</p>