First Report of Leaf Spot of Barley Caused by Drechslera gigantea in the United States

Abstract

In December 2016 in Texas, extensive leaf spots (50% incidence with 2 to 8% leaf area affected) occurred on an experimental trial of barley (Hordeum secale var. ‘Wintmalt’) in Burleson county. The leaf spots were oval to elongated, 5 to 15 mm long, with a white to light brown center and a dark brown margin. Dematiaceous conidia 150 to 550 μm long × 15 to 18 μm wide with 3 to 12 septa, borne singly on unbranched conidiophores were observed in these lesions. Conidia had bipolar germination with multiple germ tubes. These features were consistent with the description of Drechslera gigantea (Drechsler 1923). Leaf pieces were placed in 10% NaOCl for 30 seconds, washed twice with sterile, distilled water and immediately blotted dry with a paper towel. The margins of lesions (2 mm2) were excised with a scalpel, placed onto water agar with streptomycin (WA), and incubated at 25oC. Dematiaceous mycelia were consistently isolated from plated lesions. Sporulation did not occur on V8 agar transfers, but did occur on ...