Patterns of accumulation of wheat gluten proteins during kernel development in response to weather variation

Investigating the patterns of variation of wheat gluten proteins during kernel development in relation to weather parameters acquired concurrently, should generate considerable worthwhile new knowledge on the environmental influences and biochemical nature of wheat quality variation for breadmaking. That investigation represented the focus of this thesis research.;Accumulation of total protein, and constituent protein fractions (gliadin, small polymeric glutenin, large polymeric glutenin, and residue) during kernel development were substantially affected by site-year differences in weather, although a common pattern of variation emerged confirmed the asynchronous nature of wheat protein synthesis. A continuously increasing ratio of glutenin to gliadin during kernel development also indicated a basic difference in regulation of gliadin and glutenin synthesis.;Insoluble glutenin (large glutenin polymers) started to form in general in significant amounts much later than that for gliadins, beginning around 25 DAA, but at a higher rate. However, for one growing location (2003 Swift Current) where kernel development was accelerated, insoluble glutenin began to form at a high rate at about 15 DAA, but still later than that for soluble glutenin at that location. Formation of insoluble glutenin invariably lagged behind that of soluble glutenin from 3 to 12 days depending on genotype and growing location. No peak accumulation was observed for insoluble glutenin, which continued to increase, but at a slower pace, until maturity. As well, the proportion of insoluble glutenin increased at the same time that the proportion of soluble glutenin decreased towards the latter part of kernel development, suggesting that the two events were mechanistically related, i.e. aggregation of smaller polymers (soluble glutenin) leads to formation of larger polymers (insoluble glutenin).;Like the parent glutenin fraction, accumulation patterns for constituent HMW glutenin subunit composition were highly influenced by weather-induced site-year effects and some different trends were observed for individual HMW-GS loci. Most notable was over-expressed Bx7 subunit of AC Vista as it accumulated at a much higher rate compared to the other four HMW-GS in its complement. HMW-GS Dx5 and Bx7* of Superb also accumulated at a faster rate compared to the other three HMW-GS. These effects were consistent among site-years. Small but apparently significant differences in relative rates of synthesis of Superb HMW-GS among site-years towards the end of the kernel development were observed.;Site-years produced very different weather conditions during the growing season and grain development periods resulting in substantial differences in grain filling duration and accumulation patterns of total protein and protein fractions. For the most part, there was relatively little difference in response between the two genotypes used in the study, despite differences in their HMW-GS composition. The very large range in total protein content at maturity across site-years (∼ 9-17%) was very compelling and indicated the considerable influence that crop season weather can have molecular mechanisms of grain development and wheat quality in general.;Identifying site-year independent trends in weather relationships to protein accumulation patterns during kernel development was challenging. Weather factors that were site characteristics included solar radiation (but not air temperature), wind speed (but not evapotranspiration), water demand, and water deficit; all had higher values in one location (Swift Current) compared to another (Winnipeg) averaged across years. In contrast, precipitation and air temperature were growing season characteristics. Rainfall was a poor predictor of protein accumulation patterns. Poor results were obtained were found when protein accumulation was examined for weather parameters varying by calendar days (i.e. DAA). When protein accumulation was expressed as percent of total protein and was analyzed in response to cumulative temperature-related weather parameters, such as thermal time (e.g. ODDS) strong site-year independent relationships were observed for gliadin, soluble glutenin and insoluble glutenin fractions. (Abstract shortened by UMI.)...