Triticale (× Triticosecale Wittmack), developed years ago by plant breeders, is a cross between wheat (Triticum sp. L.) and rye [Secale cereale L. (M. Bieb)], that combines characteristics of their parental crops. For instance, as regard to bread-making quality, the amount of protein and gluten strongly correlates with strength and elasticity of the dough in wheat. However, in triticale, this correlation is lower because part of the protein comes from rye lacking the capacity to form gluten (Skovmand et al., 1984). Considering nutritional qualities, the main triticale grain component is starch with similar content to its parent, but with a better balance composition of amino acids showing advantages over the remaining crops (Villegas et al., 1980). Regarding physical characteristics and chemical composition of grains such as protein content, crude fiber, ether extract, free sugars, and ash, triticale is in general intermediate between wheat and rye (Peña, 2004). All these characteristics allow that triticale not only is used as animal feed but also for human food in the preparation of baking products, such as different types of bread, noodles, and soft-wheat type products (Oliete et al., 2010).

The capacity of producing a high amount of biomass and grain yield and the ability to adapt to different soils and climatic conditions allow the expansion of triticale to different regions. Hence, this crop is sown in different countries. Poland is the major producer with a production of 5.31 million tons (MT) followed by Germany (2.32 MT), Belarus (1.61 MT), France (1.59 MT) and China (0.98 MT) (http://www.fao.org/faostat/es/?#data/QC). In Argentina, 499,300 ha were destined to triticale during the 2017/2018 harvest season with a production of 15,205 kg for human consumption and the remaining used for animal feed (http://datosestimaciones.magyp.gob.ar/). Last years, the global triticale production increased due to be a good source of protein and energy used mainly for animal feed.

Over a long time, triticale was considered more resistant to diseases than wheat and rye. Due to the expansion of the area sown and the cultivation time, the same pathogens present in its parents spread in this crop losing this acquired advantage (Arseniuk, 1996). Several diseases caused mainly by species belonging to Alternaria, Bipolaris, Dreschlera, and Fusarium genera have been reported in triticale (Arseniuk, 1996). When environmental conditions such as temperature and humidity are optimal for its occurrence, Fusarium head blight (FHB) is the prevalent disease in crops, which leads mainly to a reduction in yield and quality of grains. The most common pathogen able to cause this disease is F. graminearum s.s., whose presence has been reported in wheat, barley, and rye, among others. This species, together with at least other 15 species, is a member of the Fusarium graminearum species complex (FGSC), with F. graminearum s.s. being the most common species found in grasses (Aoki et al., 2012). Outside of this complex, F. avenaceum, F. culmorum, and F. poae have been frequently isolated from plants with FHB symptoms (Reis & Carmona, 2002). Other species known as F. pseudograminearum is mainly responsible for Fusarium crown rot, a prevalent disease where dry climatic conditions and conservation-farming practices are prevalent. The presence of this pathogen may interfere with the water and nutrient transports in the plants producing unfilled grains and plant death (Desmond et al., 2006).

The presence of Fusarium spp. leads to mycotoxin production whenever the climatic conditions are optimal to allow that the pathogen produces these secondary metabolites. These mycotoxins have a different impact on consumers depending on the type of mycotoxin produced. Trichothecenes are the most important group of Fusarium mycotoxins strongly associated with chronic and fatal toxicoses of humans and animals being deoxynivalenol (DON) and nivalenol (NIV) the most prevalent in different substrates (Desjardins & Proctor, 2007). Zearalenones (ZEA) are other mycotoxins structurally different to trichothecenes and acutely less toxic, which have not been associated with any fatal mycotoxicoses. Each Fusarium species has the genetic potential to produce different mycotoxins, whose production will depend on the environmental conditions present during the pathogen development. A correct morphological and molecular characterization is needed to identify the causal agent of the disease and thus know what mycotoxin could be present if the temperature and humidity conditions are optimal for mycotoxin production. Therefore, the objective of this study was to report the occurrence of F. graminearum s.s. on triticale grains from field samples in Argentina and the potential mycotoxin production for these isolates.

Based on morphological characteristics, the isolates obtained from triticale were identified as F. graminearum (Schw.). The presence of sporodochia formed by macroconidia with 5-6 septa with a width average value of 4.5-5 µm and a length average value of 50-60 µm was visualized. Moreover, abundant chlamydospore presence were visualized, which are frequently found in the macroconidia, while microconidia were not found (Leslie & Summerell, 2006). The results of F. graminearum specific PCR amplified a fragment of 400-500 pb as expected according to Nicholson et al. (1998). To confirm molecularly our results, the final sequences of red and tri101 fragments of T1 and T2 isolates were compared by using BLAST tool of the NCBI. The sequences of T1 and T2 isolates of red fragments were submitted to GenBank under the following accession numbers: MH753697 and MH753698, respectively, showing 100% homology with KT334553.1, EF428773.1, and DQ925703.1. With regard to tri101 fragments, these were submitted under MH753700 (T1) and MH753701 (T2) accession numbers showing 100% homology with KX774700.1, KX774428.1, and KX774497.1. The T1 and T2 isolates were deposited on BIOLAB fungal collection. The results of Koch’s postulates confirmed that F. graminearum s.s. was able to infect triticale spikes being re-isolated from inoculated spikes. The symptoms were firstly observed at 2 dpi with mycelial growth on anthers (Fig. 2B). At 4 dpi, spikelets were completely affected (Fig. 2C), being the spike totally affected at 14 dpi (Fig 2E). At physiological maturity, grains were severely affected showing mycelial growth and unfilled grains (Fig. 2F). Therefore, this is the first report that shows the presence of F. graminearum s.s. in triticale in Argentina. Although several works have been developed using different crops inoculated with F. graminearum (barley, oat, rye, triticale, and wheat), scarce information are available about the natural occurrence of F. graminearum s.s. in triticale (Logrieco et al., 1990; Langevin et al., 2004; Ferreira Geraldo et al., 2006). Moreover, our results showed that both isolates amplified the 708 bp and 525 bp fragment corresponding to 15-ADON and DON genotypes, respectively, while no amplification was observed for 3-ADON and NIV genotypes (Fig. 3A). Confirming these results, the 282 bp fragment was also visualized by using the primers based on the tri13 genes, while no products were observed for NIV genotypes (Fig. 3B). As regard to ZEA production, T1 and T2 showed a 280 bp fragment associated with the potential to produce this mycotoxin (Fig. 3C). The potential capacity of producing my cotoxins such as 15-ADON and ZEA could have a severe impact on consumer health. DON has been reported to be protein synthesis inhibitors targeting dividing cells such as leukocytes causing altered response immunity on consumers, while ZEA is responsible of pathological changes in the reproductive system (Chung et al., 2003; Böhm et al., 2010). In southern Brazil, the production of mycotoxins by F. graminearum in small cereals was evaluated by Ferreira Geraldo et al. (2006). In this study, seven isolates were isolated from triticale seeds and the DON and ZEA production in vitro was detected. The response of winter and spring triticale genotypes was evaluated against the natural source of F. graminearum inoculum at five sites across Canada (Veitch et al., 2008). The results showed a high susceptibility of both triticale genotypes to Fusarium with a considerable DON contamination. Future works are needed with the aim to evaluate the presence of pathogens in this promising crop to know its behavior and hence estimate what mycotoxins could be present in triticale grains.