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Wheat Information Service
Number 76: 50-52(1993)


Effect of Fusarium mycotoxins on wheat response to Fusarium head blight

Zh. Atanassov1, C. Nakamura1, T. Yoshizawa2, H. Kato1, K. Murai3 and C. Kaneda1

1 Faculty of Agriculture, Kobe University, Nada-ku, Kobe 657, Japan
2 Faculty of Agriculture, Kagawa University, Kagawa 761-07, Japan
3 Sumitomo Chemical Co., Takarazuka, 665, Japan


Fusarium head blight of wheat and other cereals caused by some Fusarium species is one of the most serious disease problems worldwide since this disease causes large economic losses and mostly because the different strains of this fungus produce a variety of toxic metabolites (mycotoxins) that can affect human health and animal productivity (Snijders1990). There are many problems that should be solved in Fusarium head blight. However, little is known about the genetic system of resistance to this disease and especially about the role of Fusarium mycotoxins in determining strains' pathogenicity, plant response and correlation between them.

Two wheat lines which showed good field-resistance in the experimental field of the Institute for Wheat and Sunflower, Bulgaria were crossed with four susceptible Bulgarian cultivars. These six wheat lines, their F1's and Nobeoka Bozu, a Japanese resistant variety, were used in our investigations. Before the experiment, thirty strains from seven Fusarium species were examined for their abilities to produce mycotoxins on rice and wheat cultures and six Fusarium strains from three different species were selected according to the different types and amounts of mycotoxins produced on rice culture. The species differentiation in their mycotoxin productivity was in accordance with the previous reports (Ichinoe et al 1985).

Plants were grown in a glasshouse and fifteen spikes per combination were artificially inoculated at anthesis with each Fusarium strain by spraying 2 ml suspension containing 105-6 macro-conidia/ml. Three criteria were used in evaluating wheat response to Fusarium head blight, ie, reduction of seed set, reduction of seed weight and mycotoxin accumulation in the infected grains. Mycotoxins were extracted with (3:1) acetonitrile/water, purified by Florisil column and analysed by GCMS and HPLC. Different mixtures of mycotoxins were detected in the grains infected by different Fusarium strains (Table1), as Wang and Miller reported (1988).

A good accordance was observed between the strains' mycotoxin productivity detected on rice culture (data not shown) and mycotoxins accumulated in the infected wheat grains (Table1). Fusarium strains that showed higher mycotoxin productivity on rice culture, such as ARC-13 and KU-1615 produced higher amounts of the same types of mycotoxins in the infected grains than the other low productive strains.

A significant correlation was found between the reduction of seed weight and the amount of mycotoxins accumulated in wheat grains infected by five Fusarium strains (Fig.1). This might be expected, since the higher percentage of the heavily damaged or mouldy seeds could directly reflect on the reduction of seed weight. When the data were evaluated individually for each Fusarium strain, it was found that the correlation coefficients were higher in the higher mycotoxin productive strains such as KU-1615 and ARC-13 than in the lower productive strains such as SHIN- 996 and KU-1368.

Several wheat lines were examined under natural conditions in Kasai experimental field of Sumitomo Chemical Co. (Table 2). The results obtained based on the concentration of mycotoxins accumulated showed a significant correlation between natural and artificial conditions of infection, suggesting validity of the method applied in estimating wheat response to Fusarium head blight. The observation that the resistant lines apparently reduced the mycotoxin level in the grains, whereas susceptible lines did not and that the reaction of F1's was intermediate in most of the cases (data not shown) suggested a possible role of mycotoxin degradation in determining wheat response against Fusarium and a polygenic nature of resistance to the disease.


References

Ichinoe M et al (1985) Trichothecenes-producing Fusarium in barley and wheat in Japan. In: Trichothecenes and Other Mycotoxins, (ed: J. Lacey), pp. 21-32. John Wiley and Sons Ltd.

Snijders CHA (1990) Aspects of resistance to Fusarium head blight caused by Fusarium culmorum in wheat. Ph. D. thesis, University of Wageningen, the Netherlands.

Wang YZ and Miller JD (1988) Effects of Fusarium graminearum metabolites on wheat tissue in relation to Fusarium head blight resistance. J. Phytopathology 122,118-125.
　

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