Efeito do silício na resistência e no manejo da mancha amarela do trigo.

Abstract

The tan spot caused by Pyrenophora tritici-repentis is the main leaf spot of wheat (Triticum aestivum). As tan spot is a disease difficult to control because there are only few efficient measures to its management, in this study was evaluated the effect of the silicon (Si) application to susceptible (Fundacep Horizonte) and moderately resistant (Quartzo) wheat cultivars on the epidemiological components of the tan spot under controlled environment and, at the field, on the reduction of the disease intensity in association or not with fungicide (prothioconazole + trifloxystrobin) treatment. In the field studies, the disease severity was weekly evaluated .At the end of the crop, the yield, weight of a thousand seeds, hectolitre weight, percentage of shriveled grain and seed sanity were evaluated. In the greenhouse experiments was evaluated the incubation period, relative efficiency of infection, lesion growth rate, final length of the lesion and severity of the tan spot. In the field experiments, the leaf concentration of Si increased up to 27.8% in the plants supplied with the element in comparison to not supplied ones. This increase in leaf Si concentration was associated with the significant reduction up to 50.7, 83.3, 38.7%, respectively of the area under disease progress curve, final severity and the incidence of D. tritici-repentis in seeds. However, the hectolitre weight, the percentage of shriveled grain and weight of a thousand seeds were not influenced by Si. The application of fungicide was significant for all evaluated variables , except for leaf Si concentration. In the greenhouse experiments, the leaf Si concentration increased up to 68.5% in the plants treated with Si. In these plants, it was observed an significant increase up to 28.2% of the incubation period, and significant reduction up to 80.5, 67.2, 74.7, 87.5, 88.3, 88,2%, respectively in the lesion growth rate, area under the progress curve of the lesion growth, final length of the lesion, final severity, progress rate of the disease and area under tan spot progress curve. The genetic difference of the cultivars was also significant for all the resistance components, where the Quartzo cultivar presented the best average values regardless of the Si application. The results of this study showed the potential of Si to increase wheat plant resistance to the tan spot of the leaf, indicating that the silicate fertilization can be inserted in the integrated management of the disease.