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