--Víctor Rául Corcuera

Generally, hybrids between maize and its nearest wild relatives--the teosintes--are highly heterotic, especially when considering prolificity traits. This fact is easy to appreciate in hybrids between maize and perennial teosinte (Zea perennis) (see MNL 56:104, 1982 and MNL 57:66, 1983) and between maize and diploperennial teosinte (Z. diploperennis) (see MNL 61:63 and 61;66, 1987 and MNL 62:77, 1988). Evidently, prolificity is a most heterotic trait.

Normally, maize is a non-prolific plant, which means that it is not capable of producing several ears per plant. On the other hand, teosinte species are really very prolific, though in different intensity depending on the species considered. Nevertheless, prolificity reaches its maximum expression in interspecific hybrids between maize and its wild relatives.

Prolificity traits were measured in F1 and F2 progenies derived from crossings between maize and Balsas teosinte, maize and Guatemala teosinte, and their respective parents. The traits considered in this study were: 1) number of productive nodes per tiller (NP), 2) number of ears in the uppermost node (EUN), and 3) number of ears per tiller (ET). All of them were measured on the basis of individual plants, when these were completely mature.

The results obtained for these kinds of hybrids are very similar to those previously found in perennial teosinte-maize hybrids (see MNL 57:66, 1983) and diploperennial teosinte-maize hybrids (see MNL 62:77, 1988). These results are shown in Tables 1 to 4.

As can be seen in Tables 2 and 4, the average values found for the F1 and F2 progenies highly exceed the mid-parent. In addition the simple observation of the average values for the number of ears in the uppermost node (EUN) demonstrates that it is not only higher than the mid-parent average value, but significantly exceeds the most prolific parent values too. Even a similar fact can be pointed out if one considers the number of ears per tiller (ET) in the hybrids between maize and Balsas teosinte.

Prolificity traits frequency distribution is completely displaced to the right side, relative to their parental frequency distributions. From the results obtained, it can be settled down that prolificity traits express a high degree of heterosis, especially if one refers to number of ears in the uppermost node (EUN) and ears per tiller (ET) in hybrids between maize and Balsas teosinte.

According to the results obtained, it can be stated that prolificity traits are transgressively inherited in a positive direction (heterosis), as happens in diploperennial teosinte-maize hybrids (see MNL 62:77, 1988). It could also be added that maize-Balsas teosinte hybrids seem to be more prolific than those obtained between maize and Guatemala teosinte.

Finally it is important to point out that this particular mechanism of inheritance for prolificity traits has a high practical value, as through the utilization of wild germplasm the prolificity degree of cultivated maize could be significantly increased.

Table 1.  Means, standard deviation and ranges for prolificity traits in the OU maize inbred line (P1), Balsas teosinte (P2) and F1 and F2 populations.

Table 2.  Differences between means for prolificity traits of OU maize inbred line (P1), Balsas teosinte (P2), F1 and F2 populations and mid-parent value (MP).

Table 3.  Means, standard deviation and ranges for prolificity traits in the OU maize inbred line (P1), Guatemala teosinte (P3) and F1 and F2 populations.

Table 4.  Differences between means for prolificity traits of OU maize inbred line (P1), Guatemala teosinte (P3), F1 and F2 populations and mid-parent value (MP).

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