Gene effects in flints--evolutive cycle, plant and ear traits
--M. B. Aulicino
In Argentina and other countries, hybrids with early ripening are usually sown in areas with short growth seasons. In the last few years they have also been cultivated in other areas. In Europe, they have been widely used in places with extreme climates as a principal resource or as a second crop using late sowing throughout the autumn-summer period. In Argentina precocious or semiprecocious maizes are being cultivated successfully in marginal areas, but also in traditional areas because of their present operative and commercial advantages, especially the semiprecocious ones. Gaspé, native to Canada, presents little agronomic value but is extremely precocious.
The aim of this paper is to determine the genic effects present in Gaspé crosses with red Argentine flint inbred lines to apply this information to the orientation of breeding and selection plans. With this aim in mind, inbreds H38, P21, P465 and P1338 from INTA Pergamino and CFE from the IFSC were used as "female" parents and "Gaspé" as pollinator. For each of the 5 combinations the F1's, F2's and the backcrosses by both progenitors were obtained. Cycle, plant and ear traits such as: days to tasseling (DT), ear insertion height (EIH), number of kernels per row (NKR), number of rows per ear (NRE) and ear length (EL) were evaluated. The adjustment to the additive-dominance model (Mather and Jinks, 1977) was tried (Table 1). For the crosses which did not fit the model the simple genic effects and interaction effects were tested by the six parameters model (Table 2). Gaspé was the dominant progenitor for the trait (DT), as the negative values of the genic effect [h] demonstrate. For all the ear traits and EIH, the inbreds were dominant with the exception of CFE for the traits EIH, NRE, and EL; P1338 for EL and P21 for EIH. The crosses with P1338 and CFE adjust perfectly to the three parameters model, assuring a simple inheritance for most of the traits studied, with the exception of the trait DT for CFE. As Gaspé was designated as P2 in the model, the positive value of [h] determined that the inbreds are the carriers of most of the alleles which increase the traits studied. As the male parent "Gaspé" is common to all crosses, the differences in the results are evidently determined by a differential genetic behaviour of the inbreds. For the traits EIH, DT and NRE, the crosses with H38 and P21 presented the majority of the significant simple and interaction effects. The additive effects greatly surpassed the dominant ones for the cycle, plant and some ear traits, assuring an effective advance in conventional methods of selection. Overdominance is revealed for some ear traits, especially for the crosses with P21.
A synthetic based on these materials could be used in a breeding program to obtain precocious materials with flint characteristics.
Table 1. Mean estimates of 3 gene effects for the five crosses and chi-square values (x2).
Table 2. Means estimate of the six gene effects.
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