Cultivar and Environment on the Impact of Yellow Rust (Puccinia striiformis) in Triticale

Yellow (stripe) rust caused by Puccinia striiformis f. sp. tritici (Pst) is a major destructive fungal disease of triticale, of increasing importance in recent years, in Romania and worldwide. We tested twenty-three released triticale cultivars and breeding lines originated from the breeding program of NARDI Fundulea and twenty-five new lines selected at ARDS Teleorman in locations with higher stripe rust attack in 2023 and 2024, and observed significantly different disease scores, ranging from resistant to very susceptible. In five yield trials performed in 2023 and 2024, stripe rust had significant impact on grain yield explaining between 15 and 92% of the yield variation. In one trial, at Târgu Mureș the disease occurred unusually early and intense on young plants, and susceptible cultivars did not produce any yield. On average over six trials (three locations x two years) the correlation between rust scores and grain yield was r=- 0.84***. Best resistance to Puccinia striiformis was observed in cultivar Zaraza and in five of the new lines. Based on genealogy, we could trace the resistance sources, to the Polish semidwarf cultivar Magnat and to introgressions from Triticum aestivum cultivars which were used as parents in crosses with triticale. The deployment of disease-resistant host cultivars proved to be an efficient, economically, and environmentally sound approach to control yellow rust. We observed large yield differences between cultivars scored similarly for rust attack, suggesting differences in partial resistance and/or tolerance to the disease. Their exploitation can be, along with exploiting available sources of strong resistance genes, an additional breeding objective for reducing rust induced yield losses. The impact of stripe rust on yield was associated with lower temperatures and higher rainfall in April, which explained more than one third of the variation in coefficients of correlation between stripe rust and yield.