ANALYSIS OF HOST-PATHOGEN INTERACTION IN FUSARIUM HEAD BLIGHT OF WHEAT AND BARLEY

For analyzing the host-parasite interaction of Fusarium head blight in wheat and barley caused by Fusarium spp., a total of 104 Fusarium strains were inoculated to two varieties each of wheat and barley (Exp. 1), half of the strains were reexamined in the next year (Exp. 2), and 12 strains were inoculated to ten varieties each of wheat and barley (Exp. 3). Cut-spike inoculation method developed by the authors was adopted and the infection rate was evaluated based on the percentage of infected florets (barley) or infected spikelets (wheat). Correlation coefficient for the infection rate between two years was exceeded 0.6 indicating the stable expression of the disease reaction. In Exp. 1 and 2, analysis of variance for the infection rate revealed that the host-pathogen interaction was statistically significant. But the strain X within barley and strain X within wheat interaction was very small and almost statistically insignificant, indicating that differentiation of the pathogenicity within the host species was not appreciable. Although the interaction of strain X (barley vs. wheat) was statistically significant, its variance ratio was as small as about 2. The correlation coefficients between the hosts were very high (more than 0.8), and the principal component analysis revealed that the first component showing the general pathogenicity accounted for more than 89% of the total variation whereas the second principal component reflecting the specific pathogenicity between barley and wheat accounted for only 5 similar to 6% of the total variation. In Exp. 3, strain X (barley vs. wheat) interaction was statistically significant and two strains, SHIN-996 and ARC-2124-1, showed a higher pathogenicity to barley than to wheat. However the correlation coefficients among the strains and the hosts were generally high, the second principal component showing the difference between barley and wheat accounted for only 4% of the total variation. Therefore in the Fusarium head blight we can conclude the followings : 1) Strain X within host-species interaction is very small. 2) Strain X (barley vs. wheat) interaction is statistically significant but the host-specific variation is very small in comparison with the variation of the general pathogenisity.