LAUSR

Yellow rust caused by Puccinia striiformis f. sp. tritici, is a foliar wheat disease that cause significant yield losses in Portuguese bread and durum wheat yield, mainly in recent years. The strategies to disease control include cultural practices (crop rotation, use of balanced fertilizers, framework of planting dates), use of resistant varieties and fungicide application. The concern of modern plant breeding has been the improvement of new varieties with escape behavior to diseases and/or genetic resistance, but currently, the use of chemical produts offers a pratical and rapid response solution to combat rust outbreaks. In the present study, field experiments were conducted from 2013/2014 to 2016/2017 growing seasons to evaluate: 1) resistance levels against yellow rust in some bread and durum wheat varieties widely used by Portuguese farmers; 2) the opportunity of application of fungicide in the control of Puccinia striiformis in two stages of plant development; 3) gains obtained in each situation in yield and thousand kernel weight (TKW) compared to the control without fungicide application. This study allows to conclude that the need to use fungicide sprays it´s related not only on the carry over of rust inoculum in crop, but also of the races/strains of P. striiformis occurring in a region, the crop growth stage at time of symptom appearance and on variety level of resistance.