A higher level of efficiency in the production of doubled-haploids must be achieved if this procedure is to be beneficial in plant improvement. Of equal importance is the development of protocols, which are not genotypic specific and result in progeny that represent a random sample of gametes from the parental lines. To address these issues seven diverse winter wheat genotypes and a spring wheat, previously shown to be responsive in haploid plant production from anther culture, represented the experimental material. Two methods of generating haploid plants were employed. These were anther culture and the intergeneric hybridization of wheat with maize. Three induction media (MN6, P2 and Liang's) in liquid and semi-solid forms were employed with anther culture a direct culture. A modified floret culture along with different concentrations (20 and 100 ppm) and mode of application of 2,4-D were examined for the wheat x maize approach, Measurements included callus and embryo production and haploid plantlet regeneration. Two winter genotypes 'Gene' and 'Yamhill' did not respond to the anther culture methodology. For responsive genotypes MN6 was superior to P2 and Liang's medium for the traits measured. In contrast 'Chris' the spring wheat was more responsive for plantlet regeneration on P2 medium. No differences in haploid plantlet regeneration for the traits were observed between liquid and semi-solid medium forms. For the wheat x maize approach, direct culture was superior to the modified floret culture for embryo and haploid plantlet production. No differences were found in either 2,4-D concentration or whether 2,4-D was applied through tiller injection or placed as droplets on the florets. The wheat x maize approach was superior to anther culture for both embryo and green haploid plant production based on the number of florets used. Albino plants were produced in all responsive genotypes with anther culture. In contrast, no albino plants were regenerated with the wheat x maize approach. All genotypes were responsive for both embryo production and haploid plant regeneration in the intercrossing approach. In addition no regeneration distortion was observed for specific population employing this protocol. The wheat x maize approach was superior to anther culture for embryo production. This was also true for green haploid production based on the number of florets used. A higher proportion of albino plants was also observed when anther culture was employed. A further attribute of the wheat x maize approach was that all genotypes tested were responsive to embryo and haploid production. It was also revealed that no segregation distortion was present in three doubled haploid populations developed from wheat x maize crosses. / Graduation date: 1999

The lack of information regarding the inheritance of the duration and rate of grain filling, and the possible relationship between grain fill and grain protein content in wheat prompted this study. Early maturing Chinese cultivars, 'AI Feng 2' and 'CB 83-52', and late maturing cultivars adapted to Oregon, 'Stephens' and 'Yamhill Dwarf', were examined for vernalization and photoperiod responses. Progeny from a diallel cross of the genotypes was evaluated for grain filling parameters, grain protein content and other agronomic traits for two years. 'Yamhill Dwarf' required six weeks of vernalization, while other cultivars needed only four weeks. The two Oregon developed genotypes were more sensitive to photoperiod than Chinese genotypes. Variation in developmental patterns among genotypes was related to differences in leaf number, spikelet number, rate of spikelet initiation, and rate of grain fill. Compared to solid planting, space-planting reduced the grain filling period. Significant genotypic variation for grain filling rate, duration, and kernel weight was observed in both seasons. Genotype X year interaction was not significant for any of the grain filling traits. General combining ability effects for grain filling rate, duration, and kernel weight were much larger than specific combining ability effects. Additive gene action made the major contribution to the inheritance of the grain filling traits. However, dominance effects appeared also to be involved in the genetic control of grain filling duration and kernel weight. Narrow sense heritability estimates were high for all three grain filling traits. Results indicated that early generation selection for both duration and rate of grain fill should be effective in these populations. Rate, but not duration of grain fill was closely associated with kernel weight. There was an inverse relationship between duration and rate of grain filling. Kernel protein percentage was positively associated with duration, but negatively related to rate of the grain filling. Results suggest that starch and protein accumulations in the kernel are two highly independent processes and may not necessarily compete for assimilates or energy. It may be necessary under the environments of this study to increase the duration of the grain fill to obtain high protein content with acceptable grain yield. / Graduation date: 1993