Some traits of the male inflorescence (tassel) can have taxonomic importance, and have allowed clustering the different taxa of Zea on the basis of traits not traditionally used (Doebley and Iltis, Amer. J. Bot. 67:982, 1980). The study of interspecific hybrids between taxa belonging to the 2 different sections in which Doebley and Iltis have divided the genus Zea offers the possibility of obtaining information that contributes to supporting the force of the specific value of those traits.
We have previously studied (see MNL 58:122) the inheritance mechanism of 3 different tassel traits which have taxonomic value in perennial teosinte (Zea perennis) maize hybrids. This time we have repeated once more the study of those traits in hybrids between taxa belonging to the 2 different sections of the genus Zea, but replacing perennial teosinte with diploperennial teosinte (Z. diploperennis) as representative of the Sect. Luxuriantes and using maize as representative of Sect. Zea.
Four quantitative tassel traits were evaluated both in progenies derived from the crossing between diploperennial teosinte and maize, and their respective parents. The traits we studied are: 1) tassel branch number (TBN), 2) tassel branching axis length (TBAL), 3) tassel central spike length (TCEL) and 4) lateral tassel branch internode length (LTBIL) (see Table 1).
For the 3 traits of specific value (TCEL was not used by Doebley and Iltis) the parents differ significantly between themselves. On one side we have maize with high TBN and long TBAL and TBIL, on the other one there is diploperennial teosinte with low TBN and short TBAL and TBIL.
In tassel branch number (TBN) the results obtained let us deduce that a low number (teosinte) is dominant over a high number (maize). This phenomenon can also be seen for TBAL when traits are closely entailed. The average values of both traits for F1 and F2 progenies are significantly lower than the mid-parent value (see Table 2).
The way in which these traits (TBN and TBAL) are inherited is different from that previously reported for perennial teosinte-maize hybrids (see MNL 58:122). By the opposite, the TBIL trait is inherited in a similar way in both kinds of hybrids: the F1 and F2 average values are intermediate when they are compared to their respective parent average values, and the F2 frequency distribution nearly reaches the parents' extreme values, by which one can deduce, as was previously remarked (see MNL 58:122), that this trait is quantitatively inherited and possibly that the action of additive genes is predominating.
The fact that TBN and TBAL are inherited in a very different way, depending on the type of teosinte used in the cross, though all these species belong to the same section of the genus Zea, and the great variability shown by maize for these traits, offers an infinite number of different inheritance possibilities derived from a great deal of possible genetic combinations.
These results coinciding with our previous publications (see MNL 58:122), let us suppose that from the 3 different traits studied, only one has specific value (TBIL). Nevertheless, it is necessary to analyze a greater number of hybrid combinations between representatives of both sections of the genus Zea to obtain strong definitive conclusions. As there is a great diversity in maize, we think that probably the better thing would be analyzing hybrids between the different teosintes to study the specific traits.
Table 1. Number of plants (N), means and ranges for tassel traits in diploperennial teosinte (M), Ever-green maize (Eg) and F1 and F2 populations.
Table 2. Differences between means for tassel traits of diploperennial teosinte (M), Ever-green maize (Eg), F1 and F2 populations and mid parent values (MP).
Victor R. Corcuera and Jorge L. Magoja
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