Biosynthesis of Deoxynivalenol in Spikelets of Barley Inoculated with Macroconidia of Fusarium graminearum

ABSTRACT This research examined the biosynthesis of deoxynivalenol (DON) and 15-acetyldeoxynivalenol (15-ADON) in barley spikelets inoculated with macroconidia of Fusarium graminearum (Group-II). Investigations were conducted to determine if these toxins were present in macroconidia of the pathogen prior to inoculating barley spikelets. Extracts of macroconidia cultured from mung bean agar were analyzed using gas chromatography-mass spectrometry. Neither DON or 15-ADON was detected in three isolates' macroconidia when compared with macroconidia-DON-matrix standards adjusted to 100, 200, 300, and 400 ng/g with a detection limit of 100 ng/g. Mean recovery of DON that was added to macroconidia was 89.5%. The same isolates were pathogenic on barley cultivars Robust (moderately susceptible) and Chevron (moderately resistant) and produced DON (0 to 3.69 ng/g) and 15-ADON (detected but not quantified) when grown in rice culture. Greenhouse experiments were performed to determine when DON and 15-ADON were detecta...