As we have mentioned earlier (see MNL 62:80), perennial teosinte (Zea perennis) introgression in maize produces a positive effect in the protein level of the kernel which, added to the variability produced for this character, would allow selection of maize with a protein content higher than that of those cultivated at the moment.

With the aim of obtaining more information about the relationship between kernel protein content and yield, 108 S1 lines and 11 half sib families derived from the introgressed population were studied. Together with commercial hybrids (controls), they were part of a trial plot cultivated in Llavallol during the 1987/88 growing season.

The results obtained for protein content of the complete kernel in S1, half sib families and controls (21 data) are summarized in Table 1. The S1 have a significantly higher protein content than the controls and half sib families, and the latter also exceed the commercial hybrids significantly.

Table 1. Whole kernel protein content of S1, half sib families (HS) and commercial hybrids (CH).

When the kernel protein content is correlated with a total of 28 evaluated characters of evolutive cycle, plant, ear, etc. within each type of progeny (S1 or half sib), or considering the total of both, only associations of statistical significance were detected for the characters shown in Table 2. The results obtained show an inverse association between yield and some of its components as regards protein content. It is important to point out that this relation is not significant when considered within the half sib families. This fact might seem contradictory with the data provided: why, if the protein content is associated with the yield components in a similar way, both in the S1 and the half sib, does the same not occur as regards yield?

Table 2. Correlation coefficients between some traits and whole kernel protein content (WKP).

To answer this question we should explain that in the half sib families the principal yield component is prolificity (ears per plant). Since ears per plant is not significantly associated with protein, it results that protein is not significantly associated with yield.

This constitutes a matter of great importance, for it would possibly allow us to break the inverse relation between yield and protein, at least in this particular case, and within this introgressed maize, in half sib families.

Table 3. Whole kernel protein content and grain yield considering all families and the 37, 20 and 10 more yielding families of the whole (MYF).

With the purpose of verifying whether this lack of significant association still remained when selecting high yield progenies, the comparisons practised are shown in Table 3. As it is perfectly demonstrated, the average protein content of all the families (219), does not vary significantly from that of the 37, 20 or 10 higher yield families. This fact is illustrative enough as regards the possibilities that might derive from these materials when trying to find adequate combinations between protein content and grain yield.

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