Antifungal substances produced by fungal strain Kyu-W63 from wheat leaf and its taxonomic position

Abstract

Fungal strain Kyu-W63 from a wheat leaf suppressed the development of wheat powdery mildew caused by Blumeria graminis f. sp. tritici. Nuclear magnetic resonance analysis revealed that Kyu-W63 produced two volatile substances: 5-pentyl-2-furaldehyde and 5-(4-pentenyl)-2-furaldehyde. Although the two are known to be nematicidal substances, the antifungal activity of 5-(4-pentenyl)-2-furaldehyde was first confirmed in the present study. Culture experiments revealed that synthesized 5-pentyl-2-furaldehyde had antifungal activity against three other pathogens – Fusarium oxysporum f. sp. lycopersici, Colletotrichum fragariae, Botrytis cinerea – with a minimum inhibitory concentration of 2–4 µg/ml. The two fractionated substances were also inhibitory against C. fragariae. Because the absence of spores in strain Kyu-W63 made its identification difficult, the sequence in the rDNA internal transcribed spacer (ITS) region of Kyu-W63 was compared with that of Irpex lacteus, which is known to produce these substances. Strain Kyu-W63 completely agreed with I. lacteus in terms of the ITS sequences, so strain Kyu-W63 was inferred to be I. lacteus. Two other strains of I. lacteus tested also produced the two furaldehydes and suppressed the growth of F. oxysporum f. sp. lycopersici. Both Kyu-W63 and additional strains produced the two furaldehydes on potato dextrose agar but not on water agar.