Abstract
Quality protein maize (QPM) has approximately twice tryptophan (Trp) and lysine (Lys) concentrations in protein compared to normal maize. Because several genetic systems control the protein quality of QPM, it is essential to regularly monitor Trp and/or Lys in QPM breeding programs through laboratory analysis. The objective of the study was to evaluate the capability of Near –Infrared Reflectance Spectroscopy (NIRS) method in determining tryptophan content of QPM which enhance the efficiency of QPM research efforts by partially replacing more expensive and time-consuming wet chemistry analysis. 268 maize samples were used to develop NIRS models for Tryptophan content. Standard error (SEC) and coefficient of determination for the calibration were 0.007 and 0.76 respectively. When the NIRS model was subjected to external validation with 40 S2 lines from QPM breeding populations, the standard error of prediction (SEP) for validation and coefficient of determination between NIRS and the chemical data were 0.008 and 0.84 respectively. Therefore, from the result it is confirmed that NIRS model is effective tool for screening of QPM from normal maize.
Highlights
Maize breeding programs have been focused on increasing stability and yield potential under abiotic and biotic stresses
The results showed that Near –Infrared Reflectance Spectroscopy (NIRS) data were more accurate than amino acid estimation based on crude protein regression data, but the usefulness of these calibration curves was very limited, as indicated by a ratio of performance deviation (RPD) values lower than 3, and because the ratios between the standard deviation (SD) of the reference values and the standard error of prediction for the validation curves were not published
The results showed that NIRS data were accurate enough to screen Quality protein maize (QPM) from normal maize in QPM breeding program
Summary
Maize breeding programs have been focused on increasing stability and yield potential under abiotic and biotic stresses. Multiple genetic systems control and modify the protein quality of QPM; (Gibbon et al, 2005, Krivanek et al, 2007,) Trp and/or Lys monitoring is required to ensure and maximize genetic gain in breeding programs [4]. Most QPM breeding programs routinely monitor Trp and/or Lys concentrations in protein by colorimetric methods or highperformance liquid chromatography (HPLC) [5]. The colorimetric method is less complex than HPLC but requires >20 h to complete analysis because of overnight digestion procedures (Nurit et al, 2009). These chemical analysis methods have limitations include costs, time, and method robustness [2]
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