Identification of Alternaria spp. on wheat by pathogenicity assays and sequencing

Abstract

The pathogenicity of Alternaria spp. isolated from wheat leaves collected in regions where alternaria leaf blight has been reported was compared with that of IMI reference isolates of A. triticina and A. alternata using two durum and two bread wheat genotypes. To identify isolates putatively corresponding to A. triticina , morphological and DNA sequence analyses based on ribosomal DNA from the internal transcribed spacer (ITS) region (ITS1, 5·8S rRNA gene, ITS2) and toxicity bioassays of culture filtrate were combined. Glasshouse inoculations provided reliable information to assess the pathogenicity of A. triticina isolates on wheat. Alternaria leaf blight symptoms were produced by the A. triticina isolates only on durum wheat cv. Bansi, while A. alternata , A. tenuissima and A. arborescens isolates were found to be nonpathogenic on the wheat cultivars tested. Alternaria triticina isolates were distinguished from other Alternaria species by Simmons and Roberts' sporulation pattern 6 and two to three conidia per sporulation unit associated with primary conidia bearing long (> 7 µ m) apical secondary conidiophores. Phylogenetic analysis also proved effective at discriminating wheatpathogenic A. triticina from other nonpathogenic Alternaria species. Alternaria triticina isolates yielded longer ITS sequences than A. alternata , A. tenuissima and A. arborescens isolates, leading to clear-cut differences as visualized with agarose gel electrophoresis. Additionally, only culture filtrates of A. triticina isolates caused nonspecific necrotic lesions on leaves of 3-week-old wheat plants.

Phenotypic and phylogenetic segregation of Alternaria infectoria from small-spored Alternaria species isolated from wheat in Germany and Russia

“…The identification of Alternaria species still offers remarkable difficulties and some authors urge a critical systematic revision within the genus Alternaria (Mercado Vergnes et al . ; Frisvad et al . ; Logrieco et al .…”

“…The identification of Alternaria species still offers remarkable difficulties and some authors urge a critical systematic revision within the genus Alternaria (Mercado Vergnes et al 2006;Frisvad et al 2008;Logrieco et al 2009). So far, a classification of small-spored Alternaria strains usually results from the identification of morphological characters, like growth rates on different nutrient media, colouration of colonies and numbers and shape of conidia (Simmons 1994;Andersen et al 2001Andersen et al , 2002Hong et al 2005).…”

Spotlight on the Underdogs—An Analysis of Underrepresented Alternaria Mycotoxins Formed Depending on Varying Substrate, Time and Temperature Conditions

“…Saprophytic Alternaria strains can be found on grains in storage included in postharvest spoilage processes or in the soil as microbiome members in the rhizosphere [3,4]. Pathogenic Alternaria species affect healthy plants and seeds inducing necrosis on leaves, reducing grain germination and can also cause stem cancer, leaf blight or leaf spot diseases [3,5,6]. …”

Impact of Alternaria spp. and Alternaria Toxins on Quality of Spelt Wheat

“…are cosmopolitan saprophitytic and phatogenic fungi reported on various crops causing diseases on cereals (Zur, Shimoni, Hallerman, & Kashi, 2002;Mercado Vergnes, Renard, Duveiller, & Maraite, 2006;Bensassi, Zid, Rhouma, Bacha, & Hajlaoui, 2009;Tóth et al, 2011;Andersen, Nielsen, Pinto, & Patriarca, 2015), but also fruits (Serdani, Kang, Andersen, & Crous, 2002;Tournas & Katsoudas, 2005;Magnani, De Souza, & Rodrigues-Filho, 2007;Ntasiou, Myresiotis, Konstantinou, Papadopoulou-Mourkidou, & Karaoglanidis, 2015;Andersen et al, 2015), and vegetables (Noser, Schneider, Rother, & Schmutz, 2011;Edin, 2012;Zheng, Zhao, Wang, & Wu, 2014;Andersen et al, 2015). The importance of Alternaria spp.…”