Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.) Petch], results in serious economic losses to wheat (Triticum spp.) production throughout the world. Host resistance has been considered an economically efficient method of combating this disease. Lack of effective resistance sources, however, has limited progress in the development of wheat cultivars with satisfactory levels of disease resistance. The objectives of this research were to (1) identify novel sources of FHB resistance from wheat relatives and wheat-alien species derivatives, (2) characterize chromosome constitutions of resistant derivatives using molecular cytogenetic techniques, and (3) transfer alien FHB resistance genes to adapted wheat backgrounds.; Three hundred seventy-six accessions of five cultivated tetraploid subspecies (T. turgidum) were evaluated for FHB resistance over three greenhouse seasons using the point inoculation method. Approximately 90 accessions exhibited resistance comparable to T. aestivum cv. Sumai 3, a widely used source of FHB resistance. To identify sources of resistance for hexaploid wheat, 293 wheat-alien species derivatives were evaluated over 2 greenhouse seasons. Seventy-four of these derivatives exhibited a level of resistance comparable to Sumai 3. These resistant derivatives include wheat-alien species amphiploids, synthetic hexaploid wheat lines, and wheat-alien species substitution and translocation lines.; Cytogenetic characterization was performed on four wheat-alien species derivatives with high levels of FHB resistance. Fluorescent genomic in situ hybridization (FGISH) patterns of mitotic chromosomes indicated that these derivatives are partial wheat-Thinopyrum ponticum amphiploids, each with 56 chromosomes, although with varied amounts of Th. ponticum chromatin. Hybridization between all combinations of these four amphiploids was made to determine homology between the Th. ponticum chromosomes in each of the amphiploids.; Introgression of alien resistance genes into cultivated wheat backgrounds was carried out using traditional hybridization coupled with use of the PhI gene to enhance wheat-alien chromosome translocation. Introgression lines were identified with apparently high levels of FHB resistance, minimal alien chromatin, and improved agronomic traits relative to the wheat-alien species derivatives.
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