High-quality protein maize with normal genotype: lysine content of selected inbreds

As we reported last year (MNL 57:75, 1983), we have obtained inbred lines of red flint maize with high-quality protein and normal genotype (having no floury mutant in their genetic background).

The best lines obtained have an average lysine of 3.3 g per 100 of protein in the endosperm (see Table 1). The protein and lysine contents are the average from 5 to 10 ears of each line.

The variability of lysine content in each line is low. Between lines, there exists a significant negative correlation between protein content and protein quality: high levels of lysine are found more frequently in lines with less protein content in the endosperm.

In the selection process used which was reported previously (MNL 57:75, 1983) inbred lines OU and DY which were obtained from the Instituto Fitotecnico de Santa Catalina were used as donors for the red flint feature. These lines have an average lysine content of 2.1 g per 100 g endosperm protein. Based upon the content of lysine of OU and DY lines, the increase of lysine obtained in AL lines was calculated. Notwithstanding the fact that at first sight the average increase does not appear to be spectacular, it must be pointed out that this protein quality is found in red flint maize (hard endosperm). The AL lines are phenotypically indistinguishable from the red flint lines with normal lysine content.

It appears, as has happened with modified opaque-2, that it is difficult to obtain a very high protein quality when trying to preserve totally the normal phenotype (hard endosperm). Difficulties are greater in flint maize than in dent, due to the fact that the former possess a greater proportion of hard endosperm than the latter.

Nevertheless, we believe that the protein quality of AL lines is good, considering the fact that the normal endosperm structure has not been modified and that the high protein quality has been obtained without using floury mutants, which with opaque-2 has been employed massively all over the world.

The AL lines obtained have no outstanding agronomic characteristics to permit their use in the production of hybrids. In selecting lines of high quality protein and normal genotype, the lysine content in endosperm protein has been taken into account. Therefore, the material developed has only the donor's value of high protein quality. We have actually started to use AL lines to improve the protein quality of red flint maize with outstanding agronomic characteristics.

We hope in the near future to produce red flint maize hybrids of high quality protein and normal genotype.

Table 1: Protein and lysine content of high-quality protein selected inbreds.

J. L. Magoja, A. A. Nivio and M. E. Streitenberger

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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