In 1983 (MNL 60:82), we first presented the idea of using wild germplasm with the purpose of increasing variability in maize. Although we have progressed with great success in the project of introgression using perennial teosinte (see the accompanying article),a s we have pointed out before we are also using Zea diploperennis as wild germplasm donor. With diploperennial teosinte we have never had the practical difficulties which were set out when we used the other perennial species: maize hybrids and the backcrosses are fertile, and the good viability of the kernels obtained let us derive a quantity of material with which we are actually working.
As summarized in Figure 1, interspecific hybrids between maize (as female parent) and diploperennial teosinte (as male parent), were carried out. The F1 hybrids were backcrossed by maize, obtaining the first backcross progeny (FBCP). Only one backcross was enough to get the greatest part of specific maize traits back. From the FBCP, we have begun a selection and recombination process to obtain an improved population that can be employed in the near future for practical purposes. During the growing season 1985/86, FBCP population was cultivated in three different locations of the province of Buenos Aires, among them, Pergamino. In this location, based on individual plants, a series of traits of agronomic importance were measured. The results obtained are given in Tables 1 and 2.
In general, as in the case of the maize population introgressed with perennial teosinte, this one introgressed by diploperennial teosinte shows plants which join a good deal of agronomic traits. The plants of the FBCP are vigorous, extremely prolific, and show for the greatest part of the measured traits a high variability, which includes form little developed and poor-yielding plants, up to those combining prolificacy with a big ear size and high yield.
In this population the greatest part of the plants are chiefly prolific, and for this reason ears are generally small, but despite this fact there is a wide yield and ear size variability which can be used for selection.
The results obtained up to the present in the projects of wild germplasm introgression demonstrate that the possibilities of increasing genetic variability in maize are enormous. This is especially possible when the less closely related teosintes are used. The possibility that in the near future the yield of maize can be significantly increased through non-conventional improvement methods has a solid base. It has been pointed out by several authors that the great productive efficiency of modern maize could be a direct consequence of introgressive hybridization with teosinte. If the greatest part of modern maize variability has been produced or supported by natural teosinte introgression, it is easy to suppose that nowadays we dispose of the necessary genetic resources that need to be available in the search for better yields.
Gabriela Pischedda1 and Jorge L. Magoja
1Est. Exper. Reg. Agrop. Pergamino, INTA
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