Thesis (M.S.)--Oregon State University, 1994. / Typescript (photocopy). Includes bibliographical references (leaves 61-62). Also available via the World Wide Web.

Thesis (M.S. in crop science)--Washington State University, December 2009. / Title from PDF title page (viewed on Jan. 12, 2010). "Department of Crop and Soil Sciences." Includes bibliographical references.

Hybrids between wheat and jointed goatgrass have long been presumed to be sterile; however, seed were found on hybrid plants in 1990. Field studies were conducted in 1995 and repeated in 1996. One to ten hybrid plants were planted in variable populations of wheat and jointed goatgrass to determine the rate of seed set and viability of seed produced on hybrids. An average of 2.3% of florets set seed in 1995 and 3.8% of florets set seed in 1996. Seed were set in all treatments. Hybrid population had no effect on seed set. The BC1 (first backcross) seed produced in the field studies were separated according to seed condition, full or shrivelled, and were tested for germination. Ninety-four percent of the full seed germinated in each year and 79% and 84% of the shrivelled seed germinated in 1995 and 1996, respectively. Field studies were conducted in 1996 and 1997 using seed set on hybrids grown in populations of 150 jointed goatgrass or 150 wheat plants in the previous year's field study. Ten BC1 plants were planted into plots containing 100 jointed goatgrass plants. From 0.25 to 20.29% of florets per plot set seed. Greenhouse studies were conducted in 1997 and repeated in 1998 using BC1 seed produced in the previous year's field study. Seed resulting from self-pollination occurred on 4.1% or 59 plants in 1997 and 2.1% or 16 plants in 1998. Percent seed set ranged from 0 to 80.22% on a per plant basis. Parental population and seed set on BC1 plants can not be predicted based on coleoptile color, germination day, leaf width, number of veins in the leaf, presence or number of hairs on leaf margin, plant posture, number of spikes produced, culm height, spike length, or resemblance to parents. / Graduation date: 1999

Pre-harvest sprouting in wheat costs farmers millions of dollars every year. Pre-harvest sprouting tolerance (PST) has minimized this problem, but improvement of PST is still necessary. Synthetic hexaploid wheats (synthetics) have been used as sources of genes coding for many useful traits. Two studies evaluated the PST of a synthetic (Altar 84/Aegilops tauschii) and investigated its potential as a source of PST in crosses with wheat cultivars. The first study compared the synthetic with selected wheat checks for PST and with its parent Altar 84 for the germination response of these genotypes to controlled wetting treatments applied to field-grown intact spikes and threshed seed. Spikes were rolled in wet germination paper and the percentages of germinated seed were determined after seven days. Threshed seeds in Petri dishes were wetted with water and vegetative floral tissues (chaff) extracts. Germinating seeds were counted daily for 14 days. The synthetic was more tolerant than Altar 84 and was classified as moderately sensitive. The improved PST of the synthetic over Altar 84 was attributed to Aegilops tauschii. Seed dormancy and water-soluble substances in the chaff of the synthetic and other genotypes appeared to contribute to their PST. The second study used random inbred F��� lines obtained from single and backcrosses between the synthetic (red-seeded) and the sensitive wheat cultivars Opata F��� (red-seeded) and Bacanora 88 (white-seeded). Seed coat color and germination responses of the F5 lines subjected to a five-day spike wetting treatment were evaluated. Pre-harvest sprouting tolerance was moderately to highly inheritable and largely controlled by additive gene effects in the studied populations. An association between red seed coat color and PST was observed but white recombinant lines more tolerant than their sensitive parent were obtained. The synthetic can be used to improve wheats with red and white seed coats. The potential use of the synthetic as a PST source was discussed and a breeding strategy suggested. / Graduation date: 1999

The occurrence of seed-producing wheat x jointed goatgrass hybrids in infested wheat fields suggests the possibility of gene flow between the two species. This study investigates 'Madsen' wheat x jointed goatgrass F��� and reciprocal backcross derivatives produced in experimental field plantings. Electrophoresis of the high molecular weight (HMW) glutenin seed proteins, chromosome counts, and morphological studies were used to better understand the genetics of these hybrids, and to provide a baseline for evaluating hybrids collected in natural populations. The HMW glutenin profiles are a useful diagnostic tool because the banding patterns, in the 68-120 kDa molecular weight range, are species-unique (three bands for goatgrass, four bands for wheat) and can be used to trace parentage in the hybrid seed on the basis of band contribution. Experimental hybrids show considerable diversity in banding profiles (9 patterns of three to six bands). Diversity in number of different glutenin profiles and number of subunits per seed decreases in more advanced generations (BC��� and BC���S���). Chromosome counts confirm the direction of the crosses and vary as follows: 35 chromosomes for F���; 36 to 57 for BC���; 28 to 49 for BC���; and 33 to 52 for BC���S���. A chromosome number of 28 suggests that jointed goatgrass (2n=4x=28) was the recurrent backcross pollen donor, while numbers closer to 42 and above point to wheat (2n=6x=42) as the pollen donor. Partial female fertility was found in all generations, as well as full self-fertility in BC��� and BC���S��� plants. Analysis of the HMW glutenin profiles of the progeny seeds verifies that hybridization can go in either direction, with most banding patterns similar to either jointed goatgrass or wheat. The resulting potential for gene flow from wheat to jointed goatgrass calls for continued study of these hybrid derivatives. / Graduation date: 2001

Comparative morphological and anatomical studies of the dispersal mechanisms characterizing the wheat complex (Triticum L. and Aegilops L.) have documented patterns of adaptive radiation which may have significance for evolutionary relationships. These patterns, which form an array of diverse types of diaspores among the diploid taxa, appear conceptually to have a starting point in the dimorphic inflorescence of Ae. speltoides. Separate dispersal trends, centered primarily in features of rachis disarticulation, lead in the direction of novel diaspore types for Aegilops and in the direction of domestication for Triticum. With respect to the taxonomy, this structural evidence supports the traditional Linnaean generic circumscriptions and suggests a need for a monographic revision of Triticum. In documenting the dispersal mechanisms, these studies have clarified conventional interpretations and have offered new insights on the developmental relationships linking the wild and domesticated taxa of the wheat complex. Although genetic studies were not encompassed within this research, a consideration of the genetic explanations for rachis disarticulation and glume closure suggests that the phenotypic traits typically used in genetic studies are not well understood. Given that the reticulate nature of genomic relationships in the wheats is coupled with intergrading variation and polymorphic species, a proposal is made for a broader evolutionary view than is found in the strict cladistic concept. This proposal emphasizes the need of an improved understanding of fundamental structural traits and an inclusion of these traits in evolutionary analyses. / Graduation date: 1995

Doctor of Philosophy / Department of Agronomy / Allan K. Fritz / Heat and drought stress are two of the most significant abiotic stresses limiting wheat production in the Great Plains and worldwide. Introgression of novel tolerance genes from wild relatives is a strategy which presents promise. This study examined both heat and drought tolerance from the tetraploid species Aegilops geniculata (U[superscript g]U[superscript g]M[superscript g]M[superscript g]). Additional screening for heat tolerance was conducted with the US genome species Aegilops peregrina (Hack) and Aegilops kotschyi (Boiss). A comprehensive screening system for drought tolerance was also constructed to evaluate wheat and its wild relatives. Previous reports suggested that Ae. geniculata accession TA2899 was moderately tolerant to heat stress. It had also previously been used to develop a full set of wheat-Ae. geniculata chromosome addition lines in a Chinese Spring background. To identify the chromosome(s) carrying the heat tolerance, all addition lines, as well as wheat check genotypes, were screened for post-anthesis heat tolerance in two growth chamber experiments. No chromosome addition lines were significantly different (p<0.05) from Chinese Spring, and none were found to have superior performance to the positive check cultivars. Forty-five accessions of Ae. peregrina and its close relative, Ae. kotschyi were screened in a post-anthesis heat experiment. A follow-up experiment compared the genotypes in a split-plot temperature treatment with heat and optimal growth chambers. Many accessions were similar to the control genotypes for grain fill duration, and some exceeded the wheat controls for relative chlorophyll index values on Day 12 and Day 16. TA1889 and TA1904, both Ae. peregrina accessions originating from Israel, had a higher grain fill duration across experiments than the best wheat control, and warrant further investigation. Previous reports suggested drought tolerance in Ae. geniculata. After preliminary screenings, six genotypes were selected for advanced screening and compared with three wheat cultivars. The advanced greenhouse screening system was conducted in 152cm tall PVC growth tubes. The experiment measured multiple plant responses, and had a datalogging system automatically collecting water content and matric potential of the growth media. Multiple accessions warranted further investigation, and showed potentially different modes of drought tolerance, with varying levels of stomatal resistance, biomass, and osmotic adjustment.

Master of Science / Genetics Interdepartmental Program - Agronomy / Allan K. Fritz / Wheat is increasing in importance as the global population rises; therefore, abiotic stresses adversely affecting wheat yield, such as heat stress, are of growing concern. Accessions of Aegilops speltoides, a relative of the ancestral donor of the B genome of hexaploid wheat (Triticum aestivum), have been determined to be highly heat tolerant. Six Ae. speltoides accessions were used as male donors in crosses with six hexaploid wheat lines, in all combinations, to obtain F1 amphiploid seed (ABDS = 28 chromosomes). The F1 seedlings were treated with a colchicine solution to achieve chromosome doubling (AABBDDSS = 56 chromosome doubled amphiploids) and grown out to maturity. S1 seed was collected for optimal or heat treatment after anthesis and SPAD readings were taken daily during treatment until maturity. In addition to physiological measurements, leaf tissue samples were collected from S1 plants and their respective parents for marker sequence analysis. Certain doubled amphiploids survived longer in heat treatment than their wheat parents with similar SPAD readings, but had a longer maturation time, similar to their Ae. speltoides parents. S2 seed was collected from 20 S1 plants, including one plant from the heat treatment. This heat screen demonstrates variation among the amphiploids, the genetic diversity within pedigree warrants further investigation into the viability and heat stress tolerance of the S2 seeds obtained from this experiment.

Graduation date: 2002

Doctor of Philosophy / Department of Plant Pathology / Bikram S. Gill / Segregation distortion describes the transmission of an allele or alleles of a heterozygous locus at a higher frequency than expected in a Mendelian ratio. From the organism's view, segregation distortion is the preferential retention of chromosomal blocks carrying genes beneficial to its fitness and reproductive viability. In wheat the best studied segregation distortes are those introduced from Aegilops species; these selfish genetic elements are named gametocidal (Gc) genes and the chromosomes carrying them are called Gc chromosomes. This genetic mechanism causes chromosome breakage in gametophytes lacking the Gc carrier chromosome, thus favoring its own retention in the genome. While the mode of action of the Gc genes is not yet known, they have been used extensively in wheat genetics for the development of deletion stocks, a key resource for elucidating the structure of physical regions containing important genes. The objective of this study was to develop the tools necessary to map the Gc2 gene derived from Ae. sharonensis and perform map-based cloning. Extensive physical and genetic mapping located the gametocidal gene on the distal 1% of the 4BL arm present in the T4BS[dot in middle of line]4BL-4S[sh superscript]#1L translocation chromosome. Comparative genomics using rice provided markers distal and proximal to the Gc2 locus; however, synteny broke down at the locus. The characterization of this chromosomal region has provided insight into its recombination frequency, synteny and composition; however, the dynamic architecture of the end of the chromosome has made comparative mapping of this region difficult.