Typescript, etc. / Digitized by Kansas State University Libraries

Typescript, etc.

Call number: LD2668 .T4 1952 G3 / Master of Science

Call number: LD2668 .T4 1953 M37 / Master of Science

Call number: LD2668 .T4 1951 F56 / Master of Science

Call number: LD2668 .T4 1953 A3 / Master of Science

Call number: LD2668 .T4 1953 K5 / Master of Science

Call number: LD2668 .T4 1952 D35 / Master of Science

Call number: LD2668 .T4 1950 I4 / Master of Science

Experiments were done to determine pathogenic variability and pathogenic adaptation of Septoria tritici to different wheat cultivars. Fifteen S. tritici isolates from California, Oregon, and Texas were evaluated on seedlings of two sets of geographically diverse wheat cultivars under greenhouse conditions. Significant isolate effects, cultivar effects, and isolate X cultivar interactions were found, though the interaction terms were very small compared to the main effects of isolate and cultivar. All except one isolate were virulent to two sets of cultivars, and the virulence patterns varied among the isolate-cultivar combinations. Variability in virulence among the S. tritici isolates within and between locations also was observed. The isolates were usually more virulent to the cultivars of the same geographic origin than cultivars of other locations, and this demonstrates location-specific adaptation of S. tritici. Four populations of S. tritici, secured from four winter wheat cultivars grown in a field experiment, were evaluated on seedlings of the same wheat cultivars under greenhouse conditions. Significant spore population differences, cultivar differences, and spore population X cultivar interactions were obtained. The interaction term was fairly large compared to the main effect of spore population, and it is likely that the significant interaction was due to increased virulence of S. tritici to its own cultivar of origin. The "own" spore population (inoculation with spore population obtained from the same cultivar) produced significantly larger area under disease progress curve on the cultivar of origin than the "others" (inoculation with spore populations obtained from other cultivars), suggesting cultivar-specific adaptation of S. tritici. Spore populations obtained from the two susceptible cultivars indicated general adaptation to all of the test cultivars, whereas, the spore population secured from the most resistant cultivar showed specific adaptation to its cultivar of origin. Consequences of pathogenic variability, increased virulence, and adaptation of S. tritici to wheat cultivars are discussed. / Graduation date: 1994