Graduation date: 1983

Durum wheat cultivars for North-Eastern Oregon have to be competitive in terms of their yield potential with soft white winter wheat cultivars and meet strict quality requirements of the milling industry. Combining the high yield potential of fall planted durum wheat cultivars which have an acceptable level of winter hardiness with the good quality characteristics of the spring types through winter by spring crosses is believed to be an appropriate strategy. However, to be efficient, quality traits of the breeding lines and the nature of their inheritance must be evaluated early in the breeding process. The primary objective of this study was to investigate the nature of genetic variability involving two main quality traits, namely gluten strength and carotenoid pigment content. These traits are measured by the SDS sedimentation test and by spectrophotometric analysis of pigment extracts, respectively. Total genetic variability involving grain yield, kernel weight and protein content was also studied. Combining ability analysis of a 4x4 diallel cross using two winter and two spring parents was performed according to Griffing's (1956) Model 1, method 1. Both additive and non additive type gene action controlled all traits studied. Non additive type gene action was particularly important for grain yield and kernel weight suggesting that selection for these traits should be delayed until later generations (F5 or F6). Protein and pigment content were controlled primarily by genes functioning in an additive manner although they are also influenced by significant non additive type gene action. Reciprocal effects were significant for pigment content suggesting that some maternal effect might be involved. The predominance of additive type gene action for sedimentation volume suggests that this trait can be used to screen early generation material (F2, F3) for gluten strength. F2 populations generated from the diallel cross were compared in terms of their genetic variances, potential transgressive segregation and were used to investigate the possible associations between the traits measured. Winter by spring crosses were usually characterized by an enhanced genetic variability for yield and gluten strength. Transgressive segregation for sedimentation volume was present in these crosses. Protein content was negatively associated with grain yield. No relationship between gluten strength and grain yield was observed. Gluten strength did not appear to be associated with total protein content of the grain. Sedimentation volume varied greatly, even in populations with low variability in protein content. Consequently, selection on the basis of sedimentation volume per se would not be result in selecting inadvertently agronomically unsuitable types. / Graduation date: 1991

The semi-arid regions of the Pacific Northwest are characterized by a high degree of annual temperature and precipitation variation. As a result of this climatic variation, dryland nitrogen fertilizer trials on fallow- ,wheat rotations typically demonstrate a variable response. Wheat growers in the area must not only cope with this climatic variation and its sundry effects upon their livelihood, they must also make decisions regarding the future level of anticipated climatic variation. The specific objectives were to: 1) develop a climatically responsive yield potential prediction model for soft white winter wheat from historical data at the Sherman Branch Experiment Station (Moro, OR); 2) modify this model for use on commercial fields; 3) field simulate five fallow-crop precipitation patterns characteristic of the variation found in the Sherman county area of eastern Oregon in order to test the yield potential model: 4) examine the effects of precipitation variation on nitrogen fertilizer responses, moisture storage and depletion and nitrogen mineralization; and 5) establish a quantitative relationship between precipitation/ soil moisture and nitrate accumulation in both the fallow and crop seasons. Two interacting regression models were developed to estimate grain yield levels in the 250-350 mm precipitation zone of eastern Oregon. The first model estimates yield potential from monthly precipitation and temperature values. The second model estimates the percent grain reduction due to delayed crop emergence. The grain yield model was adapted to commercial fields using a Productivity Index factor (PI). The PI is a measure of the productivity of other locations in relation to the Sherman Branch Experiment Station, using water-use-efficiency (WUE) as the basis of comparison. The field simulation of five fallow-crop precipitation patterns demonstrated that the maximum grain yield response occurred at 40 kg N (soil + fertilizer)/metric ton. The grain yield model demonstrated a 15% level of accuracy on a commercial field basis in both field trials and a survey of past production levels (1972-1980). It was hypothesized that the distribution of precipitation in the fallow and crop periods had an effect on both the amount and distribution of stored soil moisture. The field simulation demonstrated that more soil moisture was stored at the 90-240 cm depths by the patterns with more fallow season precipitation when measured in March of the crop year. Soil moisture storage and storage efficiencies fluctuated throughout the fallow and crop periods. At the cessation of the winter precipitation season in both the fallow and crop periods (March), the storage efficiency was highest when low levels of precipitation occurred. At this point in time, the mean crop period storage efficiency was 10% below the mean fallow period storage efficiency (34 and 44%, respectively) in both simulation studies. Soil moisture, temperature and immobilization requirements of crop residues interact to affect the net amount of nitrogen mineralization. The mineralization model proposed by Stanford and Smith (1972) was tested under field conditions. When the nitrogen immobilization requirement of the crop residues was included, the actual and predicted values were in agreement at the close of the 1978 fallow period. A nitrogen deficit was predicted at the 0-30 cm depth at the close of the 1980 fallow; however, the actual levels indicated a net accumulation of nitrate-nitrogen. Crop season mineralization, inferred from Mitscherlick and a-value extrapolations, in 1979 demonstrated that there was a decreasing amount of net mineralization during the crop season with increasing amounts of both fallow and crop season precipitation. Crop season mineralization in 1980 indicated that there was no net accumulation of nitrogen, rather a tie-up of 14 kg N/ha. This result reflects both the unsatisfied immobilization requirement predicted for the 1979 fallow season and crop season denitrification. / Graduation date: 1981

Wheat production in the Pacific Northwest consists mainly of the soft white wheat market class. Over 80% of this wheat is exported. In recent years there has been an increase in soft white wheat production (due in a large part to improvements in the yielding capabilities of the genotypes grown in the Pacific Northwest). To expand into different commodity markets, it would be desirable to diversify and produce wheat cultivars representing more market classes and product uses. One opportunity would be to develop cultivars representing the Hard Red Winter market class. An effort to breed high yielding, high protein Hard Red Winter wheats is now underway at Oregon State University. This research was conducted to gain a better understanding of the components (genetic and/or environmental) that determine yield and grain protein content of hard red wheat genotypes. There were two general objectives of the research. One was to study the differences in nitrogen assimilation and remobilization in a diverse group of winter wheat genotypes grown in the different agricultural environments of Oregon. The second objective was to determine the efficacy of using "hill plots" (micro-plots) as a planting method to screen for agronomic and nitrogen assimilation traits in geneticly distinct genotypes which may be used as parents in breeding efforts. Results of this study indicate that genetic differences for nitrogen assimilation and remobilization do exist, and improvements in Pacific Northwest hard red wheat genotypes can be made with appropriate selection techniques. Data also indicate that the traditional high protein wheat genotypes (from the U.S. Great Plains) do not show an advantage from a grain protein concentration standpoint when produced in the Pacific Northwest. Additionally, the environment played a critical role in determining expression of harvest index, grain protein concentration, and nitrogen harvest index. Genotype by environment interactions were high, suggesting that zone-specific varieties may need to be developed in order to attain both high grain yields and high grain protein yields. / Graduation date: 1992

Soil erosion research in the fields of agronomy, soils science and mechanics, agricultural engineering, hydrology, climatology, and other scientific disciplines has economic dimensions. In general, measurable and, at times, significant economic effects are associated with the effects of erosion in the other disciplines. Interactions between climate, soils, hydrology, and tillage practices are incorporated into a stochastic simulation model that considers twenty six combinations of five tillage systems, three initial soil depths, two soil associations, two slope classes, and two annual precipitation levels over one hundred years. The model endogeneously determines stochastic annual soil loss. Yield is a function of varying soil depth and technological advance. The model maximizes the wheat producer's objective, 100-year discounted quasi-rents from wheat production. Cumulative or total rent distributions that derive from alternative tillage systems in the different ecological circumstances are compared under stochastic dominance. In low rainfall, shallow soil areas, annual tillage systems were preferred to fallow ones, while conservation tillage dominated plow tillage. In high rainfall areas, for either shallow or deep soil, conservation tillage dominated plow tillage, while plow tillage dominated no-till. Manipulation of the tillage-associated rent distributions permitted the estimation of value-of-marginal product or willingness to pay curves (ordinary, profit-maximizing, input demand curves) that express the depth of soil as a function of its economic worth. Properties of these curves are discussed. Comparison of expected total returns and marginal returns to topsoil increments under alternative tillage systems in defined ecological circumstances paralleled the stochastic dominance results. Rankings of tillage systems by expected total returns differed between ecological areas and differed from rankings by marginal returns. Regardless of tillage system or ecological circumstances, the economic worth of each added soil increment diminished. The experiment showed that differential rates of soil loss associated with different tillage systems influence the decision to continue using or to initially invest in alternative tillages, and also influence the economically rational wheat producer's willingness to incur costs associated with soil conservation. Total and marginal rents associated with single tillages were found to vary greatly across ecological circumstances. The ability and the willingness to invest in soil conservation were somewhat divorced. This result has significance for soil conservation targeting. / Graduation date: 1986

Extensive research has been devoted to evaluating potential genotype-environment interactions. However, plant breeders are still in need of a simple way to describe how genotypes respond to different locations and years. In an environmentally diverse state like Oregon, significant genotype-environment interactions do occur The resulting lack of association between actual and genotypic potential yield performance makes it difficult to select genotypically superior lines. This study was prompted to evaluate the extent of such an interaction and compare various yield stability models. A significant genotype-environment interaction encompassing lines, environments, and years was discovered for each individual year analyzed and for the combined analysis of 1992, 1994 and 1995, and 1989 through 1994. Most lines evaluated during 1992, 1994 and 1995 were adapted to low yielding environments. However, two genotypes (OR880172 and OR880525) exhibited broad adaptation. Stephens and Mac Vicar were less adapted to the relatively high yielding Chambers site than the other genotypes tested during 1992, 1994 and 1995 due to Septoria tritici infections. The most stable genotypes during the combined 1992, 1994 and 1995 and 1989-1994 seasons were OR870831, Madsen and OR8500933H. Gene was the most desirable genotype based on stability and yield for both the combined 1992, 1994 and 1995 and 1989-1994 seasons. Due to an inability to adapt to higher yielding environments, the cultivar Rohde was the least stable genotype during the same combined periods. High and low temperatures and precipitation had minor yet significant effects on yield responses at all three sites during various periods identified. Advanced winter wheat selections and cultivars were grown in three diverse environments and compared over different time periods. Due to trial design and the objective of identifying superior genotypes from a set tested in target environments a combination of two methods, stability variance and a selection index, emerged as the most appropriate techniques. These approaches are considered the most appropriate because they use the mean of the trial as a gauge for measuring stability. / Graduation date: 1997