Developing high value oat varieties to meet milling industry requirements is constrained by a lack of detailed information on how genetic and environmental differences and interactions, management conditions and levels of N fertilizer impact on grain quality. Focusing on key milling quality characters, i.e. specific weight, kernel content, hullability and thousand grain weight, four winter oat varieties were grown under conventional and organic regimes at six geographical locations in 2012-13 and 2013-14. In addition, grain yields and oil, protein and β-glucan content of the groat was determined, and grain and groat shape parameters were measured using non-destructive methods. Results showed that there was a differential effect of environment on grain chemical and physicalparameters and statistically significantly differences for grain and groat area, length and width between varieties and locations (p-value <0.05). There were correlations between grain shape traits and kernel content, hullability and thousand grain weight. None of the varieties displayed a superior performance in all quality traits nor did any one site showed a superior performance over all values for all varieties. Interactions found for chemical quality traits between genotype and environment suggest that niche-matching varieties accordingto the chemical trait of interest could be conducted. Environments where the varieties were grown displayed variable grain quality results, suggesting that these sites are more suitable to future further investigations on grain quality differences in terms of genotype by environment interactions.On the basis of previous differential genetic and environmental effects on quality parameters found, in 2013-2014 and 2014-2015, four oat winter varieties were grown under six different levels of nitrogen fertilization. The grain was analysed by non-destructive methods in addition to specific weight, kernel content, hullability, thousand grain weight, and oil, protein and β-glucan content determinations, in order to identify the influence of nitrogen on grain quality parameters. Several non-linear responses with increasing levels of nitrogen on grain quality parameters were found. Specific weight was lower with higherlevels of nitrogen. None of the quality parameters positively affected by increasing levels of nitrogen displayed a plateau and thus it was not possible to calculate the optimal amount of nitrogen to apply for a maximal response.In order to understand the physiological mechanisms involved in panicledevelopment and architecture and how grain quality is affected, a field trial was conducted in summer 2015 and 2016. Three winter oat varieties, Tardis, Mascani and Buffalo were grown and developing grain was sampled at five different growth stages (Zadok decimal growth stage, GS). At each GS and from each variety, a panicle was sampled and divided into individual whorls and within each whorl the primary, secondary and tertiary grain were separated and analysed by non-destructive methods. Measurements of kernel content,thousand grain weight and grain and groat area, length, width and moisture content were taken. The results showed differences between the top and the bottom of the panicle in terms of maturity and also the effect of loss of moisture content during maturation. Each variety showed a unique pattern of development, although some similarities were found between them throughout grain development. Maximal grain width was reached before maximum grain length with both grain shape traits diminishing by final maturity.
- oats, grain quality, genetic and environmental factors
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Thesis, 8.52 MB, PDF
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