Crosses between Gaspé line (Zea mays L.) and perennial teosinte (Euchlaena perennis Hitch.) were performed MNL 52:37, 1978), showing high genetic affinity between the two species according to the fertility of the cross (82.5%).
The parents differ from each other in their photoperiodic response, since Gaspé blooms on the 28th day after emergence and perennial teosinte after 193 days, thus indicating a strong response to photoperiod. The hybrid F1 plants bloomed at 61.6 ± 7.2 days, showing a partial dominance of the earliness of Gaspé over its relative; furthermore the low variability is an index of uniform behavior of the F1 individuals, with low environmental modification.
The average evolutive cycle for the F2 individuals was 90.4 days, somewhat superior to the F1 but always under the average of its parents (110 days). The heritability of this character is high (0.88). On the other hand there was no recovery of the paternal extremes in the F2 population (245 plants) analyzed, indicating that the character is conditioned by several factors. The minimum number of genes that would determine earliness would be nine.
Other characters studied (pollen fertility, number of tillers per plant, and days to silking) were related among themselves and with days to blooming of the tassel (Figure 1). It is important to point out the inverse correlation, contrary to what was expected, between the number of tillers per plant and days to tassel. The relations among all the characters are highly significant, demonstrating that the earliest plants and those which have a higher number of tillers are more fertile.
As regards the character of the inflorescence, distichous ear is completely dominant over polystichous ear and pistillate spikelets unpaired are dominant over paired. Hence, there is a different genetic behavior between the annual teosintes and the perennial, since E. perennis would have a different genetic action for its specific characters with respect to annual teosinte, also showing a high prepotency in the transmission of its characters in the hybrids and descendants.
Another important aspect was the extraordinary hybrid vigor, not only in the F1 individuals but also in the F2. The high heterosis of these hybrids was quantified by comparing the characters of the F1 with those of its parents (see Table 1).
Table 1. Heterosis of F1 plants (E. perennis x Gaspé. FC/E--number
of fruit cases per ear; PN--number of productive nodes; EUN--number of
ears in the uppermost node; E/T--number of ears per tiller; E/PN--number
of ears per productive node.
| E. perennis | Gaspé | F1 |
|
||
| (a) | (b) | (c) | (c-a) | (c-b) | |
| FC/E | 5.1 | - | 9.3 | + 4.2 | - |
| PN | 2.8 | 1.6 | 4.7 | + 1.9 | + 3.1 |
| EUN | 1.0 | 1.0 | 4.8 | + 3.8 | + 3.8 |
| E/T | 2.9 | 1.6 | 25.7 | + 22.8 | + 24.1 |
| E/PN | 1.0 | 1.0 | 5.5 | + 4.5 | + 4.5 |
The hybrids have a higher number of productive nodes, a higher number of ears in the uppermost node, a higher number of ears per tiller and a higher number of fruit cases per ear than the parents.
Jorge Luis Magoja and Gabriela Nora Benito
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