Akademik Veri Yönetim Sistemi
Plant Disease, cilt.100, sa.4, ss.861, 2016 (SCI-Expanded, Scopus)
Wheat (Triticum aestivum L.) is the primary cereal crop and the main dietary staple of Kazakhstan. In 2014, five samples of 500 wheat seeds from various localities of Astana Province were analyzed for their mycoflora using an agar plate method. Seeds treated with 2% NaOCl were placed on potato dextrose agar (PDA) at the rate of 5 seeds per plate. The seeds were incubated for 7 days at 22 ± 2°C with a 12-h photoperiod. A fungus was consistently recovered from approximately 25% of the seed samples on PDA. The fungal colonies were initially white, becoming gray to black, wool-like, and growing aerial mycelium covering the entire petri dish (9 cm in diameter) within 7 days at 25°C. Conidia were unicellular, black, elliptical, and 10.0 to 15.0 µm (avg. 12.6 µm) in diameter. Morphological characteristics of the isolates were similar to those of Nigrospora oryzae (Ellis 1971). Moreover, the internal transcribed spacer (ITS) region of the ribosomal RNA was amplified by using primers ITS1 and ITS4 and sequenced (GenBank Accession No. KT429637). The sequence was compared with the GenBank database through nucleotide BLAST search and the isolate showed 98% similarity to N. oryzae (EU272488.1). On the basis of morphological data and nucleotide homology, the isolate was determined to be N. oryzae. Petri dish assay was used in the pathogenicity tests. A 6-mm colonized PDA agar plug of the Nigrospora isolate was placed in the center of a 9-mm petri plate containing 15 ml water agar. After 3 days, 5 seeds of wheat (‘Konya 2002’), previously surface disinfested for 2 min in 1% NaOCl and rinsed with sterile distilled water, were placed adjacent to the growing edge of the colonies in each petri dish in sterile conditions. A sterile, uncolonized PDA plug was used as a control. Cultures were incubated under continuous darkness for 3 days at 25°C, after which they were placed on a laboratory bench with a 12-h photoperiod. All tests were carried out with four replicates and experiments were replicated three times. After 6 days, dark brown to black lesions were clearly visible on the hypocotyls of seedlings developing from inoculated seeds but not from the controls. The pathogen was reisolated from infected hypocotyls and its identity was confirmed by morphological characteristics. Previously, N. oryzae has been isolated from several hosts worldwide (Farr and Rossman 2015) and from seeds of wheat (Clear and Patrick 1993). To our knowledge, this is the first report of N. oryzae on wheat in Kazakhstan. The geographic distribution and management options of the fungus should be investigated.