--M. B. Aulicino and J. L. Magoja
The Argentine production of corn responds, nearly as a whole, to the red or orange flint kernel type, and the greatest concentration of the cultivation is placed between parallels 32 and 35 of south latitude. Expansion of the cultivation area to larger latitudes, which took place in the last years, made it necessary to count on corn adapted to more severe environmental conditions, especially due to the shortening of the period free from freezing and the lower summer temperatures.
The cultivars disseminated in these new areas came in from abroad, mainly from France and USA having the following characteristics: precocity, lesser thermal requirements and quick ripeness of grains. The fact that these imported corns are mainly of the dent type, with a lower price in our country, raised the concern to develop improvement plans on materials with the red flint kernel type, to produce cultivars adapted to the new cultivation areas.
As part of these projects we have begun to use Gaspé germplasm to introduce greater precocity in the red flint corn traditionally cultivated in Argentina. During the 1988/89 growth season, different materials were assayed with Gaspé germplasm, among which there were F1 experimental hybrids derived from the crossings between red flint inbreds of normal cycle and Gaspé.
In one of the assays there were, as part of a complete randomized block design with 3 replicates, 15 experimental hybrids (normal cycle line x Gaspé), their corresponding progenitors and three precocious commercial hybrids, normally employed in the cultivation zones. These assays were carried out in two localities: Llavallol (our working place) and Miramar, S. E. of Buenos Aires Province and representative of the new cultivation areas.
In these assays the thermal requirements were evaluated expressed in the sum of temperatures from sowing till flowering, yield and other agronomically important traits shown in Table 1. As can be seen, Gaspé germplasm is expressed in experimental hybrids, causing a sharp reduction of the evolutive cycle (sum of temperatures) as regards the mother lines. This fact is strongly associated with the expression of number of leaves, but not with the height of the plant because there is heterosis for the latter.
If the experimental hybrids are compared to the commercial ones, we can conclude that the former are significantly more precocious and represented by plants of smaller size; therefore and in consequence, they have a significantly smaller mean grain yield. In spite of this, there exist some combinations among the ones assayed, that preserve a red flint kernel type, and whose grain yield does not differ significantly from the hybrids used as controls. This is indicative of the possibility of using Gaspé as a precocity donor, making an adequate selection for yield and kernel type (red flint).
According to the previous results it can be inferred that, previous to the beginning of an improvement programme involving Gaspé, the starting point shall be those lines, varieties, composites, etc., that express good combining ability as regards Gaspé.
Due to the experience obtained to the present, it has been proved that certain inbreds, according to their origin, combine in a better way with Gaspé than others. Thus assays carried out during 1988/89 showed that the inbreds from Pergamino-INTA (Buenos Aires Province) produce 20% higher grain yields in combinations with Gaspé than the equivalent combinations with lines coming from Llavallol.
1. Relevant traits of red flint inbreds, Gaspé, experimental
hybrids (inbreds x Gaspé) and commercial hybrids.
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