First report of Fusarium hostae causing crown rot on wheat (Triticum spp.) in Turkey

Abstract

Crown rot disease of wheat is caused by a complex of Fusarium species. To identify species associated with crown rot in Turkey, crowns and stems of bread wheat (Triticum aestivum L.) and durum wheat (T. durum Desf.) were collected from the Central and Southeast Anatolia, Black Sea and Aegean regions in summer 2013. Crown and stem pieces were surface-disinfested with 1% sodium hypochlorite solution for 3 min, rinsed three times in sterile distilled water and dried on sterile filter paper. Sections were placed on peptone PCNB agar, a selective medium for Fusarium isolation and then transferred to Synthetischer Nährstoffarmer Agar (SNA) (Leslie and Summerell, 2006). Single conidia were isolated and monosporic Fusarium sp. cultures were identified as F. hostae by sequencing the translation elongation factor 1 alpha (TEF-1α) gene region using ef1 (5’-ATGGGTAAGGARGACAAGAC-3’) and ef2 (5’-GGARGTACCAGTSATCATG3’) primers (O’Donnell et al. 1998). The TEF gene sequences were analyzed with the NCBI GenBank database. Out of 339 isolates, 20 isolates were F. hostae and 17 had a 99% match with accessions of F. hostae (eg. DQ854862). F. hostae isolates were tested for their pathogenicity on susceptible durum wheat (T. durum) cultivar Kızıltan. Plastic tubes (2.5 cm in diameter and 16 cm in height) were filled with sterile sand, soil, and peat mixture (50:40:10, v:v:v). A PDA plug (1-cm diam.) was taken from the margin of a 7-day-old culture and placed in the tube. A single pregerminated seed was placed on the PDA plug and covered with sterile soil mix. A sterile agar plug was used as a control treatment. Each treatment was replicated 3 times, and the experiment was repeated to confirm the results. Scoring for disease severity was carried out nine weeks after inoculation, using a 1-5 scale based on the percentage area of the crown area that showed brown discoloration (1: 1-9%, 2: 10-29%, 3: 30-69%, 4:70-89%, 5: 90-99%) modified from Wildermuth and McNamara (1994). Scores ranged from 1 to 3 with an average of 2.2. The scores of seven isolates were significantly greater than the non inoculated control, and six isolates had scores of 3.0. Necrosis was observed on crowns of treated plants (Supp. Fig. 1), while control treatments showed no necrotic symptoms and were rated with a score of 1. For comparison, F. culmorum scores ranged from 2 to 5, with an average of 3.25. Re-isolation was carried out from crowns of both inoculated and control plants. The re-isolated cultures were confirmed as F. hostae by comparing their morphology with known cultures of F. hostae and no culture growth was observed from control plants.