Triticale has been considered as resistant to diseases over a long time. Although, many authors perpetuate this opinion, it is no longer true.
However, in comparison to wheat and rye triticale still may look as a healthy crop, but its healthiness has been steadily declining (Arseniuk and Góral 2015). With the expansion of triticale area, and cereal area in general, disease resistance in triticale has weakened. Several fungal diseases, Septoria leaf blotch, Fusarium Head Blight, Powdery mildew and rusts have been reported in triticale crops causing a major constraint to triticale production (Haesaert et al. 2006; Miedaner et al. 2006; Oettler and Schmid 2000; Oettler et al. 2004; Walker et al. 2011).
Powdery mildew, caused by the obligate biotrophic fungus Blumeria graminis, is a major problem in cereal production. In the last decade, powdery mildew has emerged on triticale. A detailed phylogeographical study revealed that this host range expansion of wheat powdery mildew to the new host triticale occurred recently, multiple times and at different locations in Europe (Troch et al. 2012). Due to this ‘new’ disease pressure, the presence of powdery mildew resistance in current commercial triticale cultivars was recently investigated. Using molecular markers, race-specific resistance genes were identified in certain triticale cultivars (Troch et al. 2013). Furthermore, this study highlighted the narrow genetic base of triticale in relation to powdery mildew resistance, underscoring the need to deploy new sources of resistance in triticale.
For a long time, triticale had been considered relatively resistant to rusts (Mergoum et al. 2004). However, triticale disease scoring in the German National Trials during 1988-2001 showed that leaf and stripe rust occurred at a high level and were of increasing importance (Schinkel 2002). In Poland, hexaploid triticale has suffered significant losses due to leaf rust during the last decade (Sodkiewicz and Strzembicka, 2004). Also in southern Russia significant crop losses due to this disease were reported (Mikhailova et al. 2009). Analyses have revealed that leaf rust on triticale is caused by pathotypes of the wheat leaf rust fungus that have become virulent to triticale genotypes (Sodkiewicz et al. 2008). A microsatellite analysis of Puccinia triticina races in South Africa concluded that a leaf rust race collected from triticale in 2005 probably represents a mutation from an existing race, because it showed 96 % genetic homology with other races collected from wheat (Visser et al. 2012). Additionally, last years, Fusarium head blight epidemics in triticale are increasing in frequency and severity (Veitch et al. 2008).
The ability to adapt triticale to withstand multiple biotic stresses is critical to its future growth as a crop. An effective and environmentally sensitive approach to disease control involves breeding crop plants for resistance (Dodds and Rathjen 2010). Disease resistance is particularly important for low-input farming, which is common practice in triticale production.