Perennial teosinte (Z. perennis) and diploperennial teosinte (Z. diploperennis) are the most primitive taxa of Zea. Both species have primitive characters because they are perennial, have rhizomes, trapezoidal fruit cases and low number of fruit cases per spike. There is widespread confusion about which of the two species is the ancestral one, although according to different points of view, both species may be considered the most primitive.
F1 hybrids between Gaspe and each teosinte species were comparatively analyzed in order to clarify this topic. Data resulting from the observation of some characteristics of Gs x Zp and Gs x Zd hybrids are given in Table 1. Due to the fact that the same maize was used as female parent, results are highly comparable. Thus, differences in character expression may be attributed to the diverse action of the wild species' germplasm. F1 grain viability is very different: Gs x Zp are not very viable, whereas Gs x Zd develop normally. Germplasm behaviour exhibited by both species is similar in some specific characters, such as tassel central spike and female spike, whereas it is quite different in others, such as female spikelet arrangement, growth habits and rhizomes. Another group of characters, fertility, number of tillers, heterosis and prolificacy, may be considered as an index of the distance between maize and the two wild species. Shorter distance is displayed by high fertility, low number of tillers, low heterosis and less prolificacy of hybrids. In accordance with this, it may be stated that a shorter distance exists between Z. diploperennis and maize than between Z. perennis and maize.
One of the most significant aspects to consider lies in the hybrids' different heterosis linked to an evident difference in prolificacy. Consequently, it may be said that Z. perennis is the most primitive taxon of Zea and, thus, Z. diploperennis' ancestral species : Z. diploperennis is almost identical to Z. perennis in specific characteristics. Z. diploperennis stands out because of its more exuberant development and greater vigour. In our opinion, this happens on account of being derived from maize introgression into Z. perennis. Morphological and biochemical proofs as well as comparable hybrids' different behaviour suggest that Z. diploperennis could never have been the ancestral species of Z. perennis but maize introgression into Z. perennis was the predominant factor in the differentiation of these species.
Table 1: Comparison of some characters between Gaspe x Z. perennis and Gaspoe x Z. diploperennis F1 hybrids.
Jorge Luis Magoja
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