Diploperennial teosinte-maize hybrids: inheritance of evolutive cycle

At the latitude in which most cultivated maize is concentrated in Argentina (35o southern latitude), generally all the teosinte species express a strong photoperiod response, and they flower during autumn, which makes seed collection difficult. Consequently they show a long cycle. Diploperennial teosinte is a species which under these environmental conditions has a cycle 3 times longer than cultivated maize.

Evolutive cycle traits were measured in 4 different populations to obtain the necessary basic information for future projects in which diploperennial teosinte germplasm will be used for maize genetic improvement. The 4 populations studied are: diploperennial teosinte (P1); a sweet variety of maize Ever-Green (P2) and their F1 and F2 progenies derived from crossing teosinte with maize.

On the basis of individual plants, cycle traits measured are: 1) days to tassel (T), 2) days to silking (S), and 3) days to pollen (P). The results obtained are summarized in Table 1. The average values of the F1 are smaller than those of the mid-parent value (MP), being nearer to maize values. The F2 average values are higher than those of the F1 and the frequency distribution for them is wide enough to reach their parent extreme values (see Table 1 and Table 2).

The results obtained point out that cycle traits are quantitatively inherited; a short cycle (maize) is partially dominant over a long cycle (teosinte). This phenomenon indicates that these hybrids' behaviour is similar to that previously found in progenies derived from crossing between perennial teosinte and maize (see MNL 55:58, 1981).

As was obvious, in a case where a short cycle partially dominates over a long cycle, the F1 progeny average value is significantly smaller than the F2 average value (see Table 2).

These data previously shown in this paper also point out that a very low environmental influence exists over the expression of measured traits, by which we estimate that they have a high heritability. The different traits measured are closely entailed among themselves and their hereditary behaviour is similar.

Last, an interesting phenomenon to note is the degree of simultaneity in sexual maturation. Diploperennial teosinte, as the other teosintes, is a protogynous plant, but maize is generally protandrous. Opposite to other hybrids between maize and perennial teosinte, and maize-diploperennial teosinte hybrids (see MNL 58:130, 1984), the F1 progeny is protandrous as are the F2 individuals. We cannot generalize conclusions about this fact, but for this particular case protandrous trait of maize is a dominant trait.

From the results we have obtained it can be deduced that selection of short evolutive cycle individuals would be easy (previous investigations we have done demonstrate it). This fact offers a considerable advantage as you can obtain individuals derived from these interspecific crosses which have such a cycle duration that they may be grown in the field and mature under normal environmental conditions.

Table 1. Number of plants (N), means and ranges for evolutive cycle traits in diploperennial teosinte (Zd), Ever-green maize (Eg) and F1 and F2 populations.

Table 2. Differences between means for evolutive cycle traits of diploperennial teosinte(Zd), Ever-green maize (Eg), F1 and F2 populations and mid-parent values (MP).

Victor R. Corcuera1 and Jorge L. Magoja

1Fellow, Com. Inv. Cient. (CIC), Prov. Buenos Aires


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