Agronomy and Horticulture Department
Disease and Insect Resistance and Quality Characterization of Six CIMMYT Synthetic Hexaploid Wheats
Date of this Version
The germplasm sources of common wheat (Triticum aestivum L.) are eroded by selection pressures applied by plant breeders and the disappearance of landraces. The erosion causes a loss of potentially useful resistance genes, among other agronomic and quality genes. Continuously changing pathogen races and insect biotypes affecting the Great Plains requires identification of new sources of resistance. Synthetic hexaploid wheats (SHWs), T. turgidum (BBAA) x T. tauschii (DD) hybridizations, offer ways to utilize resistances trapped in the diploid and tetraploid ancestors of common wheat. Six SHWs were assayed for resistance to a variety of fungal diseases, viruses, and aphids to determine their spectrum of resistance. The six SHWs possessed a combination of resistance to races TPMK, TTTT, and the Ug99 family; races of the causal agent stem rust (Puccinia graminis f. sp. tritici); the causal agent of stripe rust (P. striiformis f. sp. tritici) race Pst-100, and the greenbug aphid [Schizaphis graminum Rondani (Homoptera: Aphididae)] biotypes E, I and K. Additionally, the high molecular weight glutenin (HMW) alleles were studied. The HMW allele combinations were different from those commonly found in current Great Plains wheats. The allele combinations included the Glu-B alleles 14+15, 20x+20y, 6*+8*, 6+8 and 7+8. Glu-D alleles present included 2+12 and 2+T2.
Upon discovering NSGC 9711 and PI 648810 were resistant to greenbug aphid, plant populations previously developed were employed to uncover the inheritance of the resistance. A series of tests were conducted using F1s, F2s, F2:3s and BC1F2s. A single dominant gene hypothesis was rejected due to an overabundance of susceptible individuals in the F2 and F2:3 populations. However, the F2:3 and BC1F2 families indicated resistance in both synthetics was from a single dominant gene, thus NSGC 9711 and PI 648810 is reported to carry a single dominant gene for resistance to greenbug biotype E.
Adviser: P. Stephen Baenziger
A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professor P. S. Baenziger. Lincoln, Nebraska: August, 2011
Copyright 2011 Kayse M Onweller