Effect of Infection Timing on Fusarium Head Blight and Mycotoxin Accumulation in Open- and Closed-Flowering Barley

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PHYTOPATHOLOGY Vol. 97, No. 9, 2007, Р. 1054-1062Megumi Yoshida, Naoyuki Kawada, and Takashi NakajimaABSTRACTBarley has two flowering types, chasmogamous (open-flowering) andcleistogamous (closed-flowering). We examined the effect of the timingof Fusarium graminearum infection on Fusarium head blight (FHB) andmycotoxin accumulation in barley cultivars with different flowering typesusing greenhouse experiments. In the first experiment, 13 cultivars werespray inoculated at two different developmental stages, and the severity ofFHB was evaluated. The effect of the timing of infection differed amongcultivars. Cleistogamous cultivars were resistant at anthesis but suscep-tible at 10 days after anthesis, whereas chasmogamous cultivars werealready susceptible at anthesis. In the second experiment, five cultivarswere inoculated at three different developmental stages and the concen-trations of deoxynivalenol (DON) and nivalenol (NIV) in mature grain were analyzed. Cleistogamous cultivars accumulated more mycotoxins (DON and NIV) when inoculated 10 or 20 days after anthesis than when inoculated at anthesis, whereas chasmogamous cultivars accumulated more mycotoxins when inoculated at anthesis. Thus, the most critical time for F. graminearum infection and mycotoxin accumulation in barley differs with cultivar, and likely is associated with the flowering type. Late infection, even without accompanied FHB symptoms, was also signifi-cant in terms of the risk of mycotoxin contamination. Additional keywords: anther, cleistogamy, Gibberella zeae, Hordeum vulgare, scab, trichothecene.