Progress 12/01/00 to 11/30/03
Outputs
Significant differences were observed among cultivars (normal, partial waxy, waxy), crop years (2001,2002), and growing environments (rain-fed, irrigated) with respect to both flour/starch characteristics and flour pasting attributes. Correlation analysis yielded further insight into the basis for flour pasting fluctuations, with emphasis on crop year and growing environment variability. In pooling cultivar data across growing locations, significant differences between crop years were observed for multiple RVA attributes, starch yields from flour, A- and B-type granule contents, and amylose values. Flour from crop year 2000, which exhibited higher mean values for flour RVA attributes (peak, breakdown, setback, final viscosities), also exhibited higher mean A-type granule content and starch yield (isolated from flour) compared to those of crop year 2001. Conversely, in pooling cultivar data across crop years, significant differences of similar magnitude to those
observed between crop years were also noted between growing environments (rain-fed, irrigated). The environment (irrigated) that exhibited the highest mean flour pasting attributes also possessed the greatest starch yields and A-type granule contents. Though both crop year and growing location exerted similar magnitude effects on flour/starch characteristics and flour pasting behavior, crop year effects were largely attributable to fluctuations experienced by the rain-fed environment. Thus, the rain-fed environment appeared to be more subject to greater environmental fluctuation (both flour pasting properties and starch attributes). Also, the crop year and/or environment that exhibited the greatest mean starch yield from flour and highest mean A-type granule content also possessed the highest mean flour pasting attributes. To further investigate the basis for the observed environmental fluctuations, correlation analysis was conducted among the measured flour/starch characteristics and
flour pasting attributes for each individual cultivar across all crop years and growing environments. For all 6 cultivars analyzed (waxy cultivars excluded due to insufficient data points), the starch yield from flour was positively correlated with flour peak viscosity (r ranged from 0.80 - 0.98). For the same 6 cultivars, 5 of 6 also exhibited a positive correlation between A-type granule content and flour final viscosity (r ranged from 0.85 - 0.90). Thus, flour pasting property environmental fluctuations were best explained by variations in flour starch content and A-type granule content. Further analysis of cultivar A- and B-type starch composition revealed that B-type granules generally possessed greater phospholipid and lesser amylose contents than their A-type counterparts. Thus, environmental fluctuations in flour A- and B-type granule content likely induce compositional and behavioral differences within the starch fraction. In conclusion, environment-induced fluctuations in
flour pasting properties were best explained by corresponding variability in flour starch yields (amount of starch isolated from flour) and indigenous flour A:B-type granule contents.
Impacts
Knowledge of factors that influence the quality of wheat for specific end-uses represents a vital element for the long-term stability of US agriculture. This work has successfully identified two primary factors (starch content and A:B-type starch granule ratio), which provide explanation for the majority of environment-induced fluctuations in wheat flour pasting properties, as elements for future intensified research focus. In particular, the ratio of the two wheat granule populations (A- and B-types) within a flour appears to influence starch composition, which leads to environmental fluctuations in flour pasting properties (differences in quality). Identification of these governing characteristics will help direct research focus toward further understanding of the basis for such quality fluctuations. Once understood, important traits could potentially be manipulated at either the production and/or genetic levels to minimize inconsistency and improve wheat
flour/starch function in food products.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Flour pasting properties for wheat grown in the Pacific Northwest fluctuate significantly according to cultivar, crop year, and growing environment. A primary objective of this project is to investigate compositional and/or structural features within wheat flour (with focus on the starch fraction) that are responsible for the variable pasting fluctuations observed among wheat cultivars grown in varied environments. This project includes eight wheat cultivars (normal, partial waxy, and waxy) of common parentage grown in diverse environments (rain-fed vs. irrigated) in two successive crop years (2000, 2001). Observed flour pasting properties were characteristic and distinct for each Granule Bound Starch Synthase I (GBSSI) gene class (normal, one gene null, two gene null, waxy). Pasting properties of cultivar flours were also significantly influenced by both environment (rain-fed vs. irrigated) and crop year. To aid explanation of genotypic and environmental
fluctuations, starches representing each cultivar/crop year/growing environment were isolated from their respective flours for further characterization. Native starch (defined as the population of starch within straight-grade flour) was isolated from cultivar (normal, partial waxy and waxy) soft white spring wheat flours using methods that maximized starch yield. Amongst the cultivars, there was a general progression toward decreased starch yields over the range of normal to full waxy. This trend was observed independent of crop year and/or growing environment effects. As anticipated, all cultivar Native starches possessed a bimodal distribution of granules. Using both laser particle sizing and image analysis techniques, a 10 micron cutoff for differentiation of A- and B-type starch granules was established. In contrasting the cultivars, there was a general tendency for partial waxy and waxy Native starches to possess an increased weight percent of the smaller B-type granules compared
to the normal starch. In comparing the cultivar Native starches, amylose (apparent, total, and lipid-complexed) and phosphorus contents generally decreased over the range of normal to waxy. Additional starch compositional and structural characterizations are underway to better understand the basis for cultivar and environment induced fluctuations.
Impacts
Knowledge of factors that influence the quality of wheat for specific end-uses represents a vital element for the long-term stability of US agriculture. The project will identify the basis for observed variability in starch rheological behavior due to genetic make-up and environmental influence. Identification of these governing characteristics will help direct research focus toward the most important starch biosynthetic pathways, which need to be understood to exert maximum control over cultivar properties. Once understood, important traits could be potentially altered at either the production and/or genetic levels to minimize inconsistency and improve flour/starch function.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
The pasting properties of flours grown in the Pacific Northwest have been shown to vary significantly by cultivar, crop year, and growing location. The goal of this work is to identify the compositional and/or structural features within the starch fraction that are responsible for the variable properties observed among flours and starches of soft white spring wheat genotypes grown under diverse environmental conditions. The raw material required for this project consists of eight wheat genotypes cultivated in two vastly different environments (rain-fed vs. irrigated) over two successive crop years (2000, 2001). Wheat for this project was provided by a collaborator at the University of Idaho. However, the initiation of the project was unavoidably delayed due to the length of time required to obtain milled flour samples for our investigation. Thus, a one-year, no cost extension was obtained. Wheat representing each of the eight selected genotypes from both the 2000 and
2001 crop years has been received and milled to flour. Native starch, which represents all starch present within a flour, is presently being isolated from flour for each cultivar/crop year/growing location combination as initially proposed. A portion of each isolated Native starch will also be subdivided according to granule size into its respective A- and B- type granule fractions. Native, A- type, and B-type starch granule fractions representing each cultivar/crop year/growing location combination will be characterized with regard to chemical composition, granule size, and physical properties. Compositional and/or structural features observed within the starch fraction will be related back to the properties of the original flour. Work on the project is progressing as planned with no further delays anticipated.
Impacts
Knowledge of factors that influence the quality of wheat for specific end-uses represents a vital element for the long-term stability of US agriculture. The proposed work is designed to further identify the basis for observed variability in starch rheological behavior due to genetic makeup and environmental influence. Identification of these governing characteristics will help direct research focus toward the most important starch biosynthetic pathways, which need to be understood to exert maximum control over cultivar properties. Once understood, important traits could be potentially altered at either the production and/or genetic levels to minimize inconsistency and improve function.
Publications
- No publications reported this period
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