From a maize population native to the Puna (Jujuy, Argentina) and cultivated in Llavallol, several S1 lines were obtained by selfing. Whole kernels of thirty of them were analyzed for protein content (WKP), lysine content (WKL) and tryptophan content (WKT); the endosperm was also analyzed for protein content (EP), lysine content (EL) and tryptophan content (ET).
This maize population named Puna, as mentioned by Vorano (IDIA 32:13, 1976), consists of early plants cultivated at 3500 m above sea-level, and possesses the interesting characteristics of having low thermic and hydric requirements and very high capacity of mesocotyl elongation. From the lines already studied, the greater part (25) have hard endosperm, and a coat of variable thickness of hard endosperm is found in all the kernel periphery. Four lines are of the dent type and only one has totally floury endosperm.
Table 1 is a summary of the results of the chemical analysis, wherein variation can be observed in lysine as well as in tryptophan contents, the highest values of these amino acids being approximately similar to those conditioned by mutants of high protein quality. What is really important is the fact that high levels of lysine and tryptophan are not associated with floury endosperm structure. Some S1 lines with high lysine and tryptophan levels have been selected, with a hard endosperm, as shown in Figure 1.
The biochemical characteristics already studied correlate with one another as stipulated in Table 2. From these results it can be deduced that the protein quality (lysine and tryptophan levels) is inversely associated with the protein content. There is a significant association between protein and lysine. We are actually working on the selection of high-quality protein and hard endosperm lines, and we have carried out crosses with normal lines in order to study the inheritance of that character.
This is the third time we communicate the findings of maize of hard endosperm, which are not related to each other and bear high-quality protein. The first communication was by Magoja (MNL 52:37, 1978), the second by Magoja (Communic. Direc. Inv. U.N.L.Z. 1:2, 1978) and the third presented herein. The results obtained up to the present allow us to suppose that maize protein quality may be improved without modifying the endosperm's structure and without the use of floury mutants; and that the Puna maize studied constitutes a genetic reserve which may be employed to improve the lysine and tryptophan levels of maize endosperm, without affecting its normal corneous phenotype.
Angel Alberto Nivio and Jorge Luis Magoja
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