Heterosis in maize-perennial teosinte hybrids

The hybrids between perennial teosinte (Euchlaena perennis = Zea perennis) and maize (Zea mays) show a surprising vigor that draws our attention. In order to quantify the differences between the hybrids and their progenitors, a series of measurements were made in an F1 population (88 plants) coming from the same number of hybrid seeds obtained when crossing perennial teosinte with the Gaspe line. The same characters were taken in the progenitors and hybrids in order to enable the comparison. The characters studied were flag leaf length (FLL) and flag leaf width (FLW). The leaf length (LL), leaf width (LW) and the sheath length (SL) were measured in the most developed leaf of each stalk, usually the fourth or fifth counting from the apex of the F1 plants. The ratio length/width (L/W) and the leaf area (LA) = 3/4 L x W were calculated. The tassel central spike length (TCEL), the length of lowermost tassel branch (LLTB), the number of tassel branches (TB), the plant height (PH), the number of nodes per tiller (N/T), the number of productive nodes (PN), the number of ears in the uppermost node (EUN), the number of ears per tiller (E/T), the number of fruit cases per ear (FC/E) and the number of tillers per plant (T/P), were measured. The stalk diameter (SD) was measured just below the most developed leaf. The comparisons between the values of the F1 and their progenitors are shown in Tables 1 and 2.

F1 plants are generally much more similar to perennial teosinte than to maize, but with a more exuberant development. They are completely perennial, blooming annually and for the characters of the inflorescence the teosinte is completely dominant. From these results it can be inferred that in general F1 plants differ significantly, with higher values for the characters studied than those of their progenitors.

Many characters which in the hybrids are expressed in a superlative degree may not, perhaps, be an expression of heterosis because they do not condition a greater biologic efficiency. Among these, the greater height and dimension of their leaves could be included. Nevertheless, the high prolificity that they show is a potential productive capacity that exceeds that of their progenitors. It is called "potential productive capacity" because it is conditioned by its fertility. If prolificity and sterility are not related characters, it is possible to select prolific and fertile individuals. The hybrids' prolificity is very high and it is because of a higher number of productive nodes (PN), spikes per node and of spikes per stalk (E/T).

From the results obtained it can be inferred that the highest heterosis in the hybrids between perennial teosinte and maize is the high prolificity that they show.

Table 1.

Table 2.

Jorge Luis Magoia and Gabriela Nora Benito

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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