The simultaneous improvement of the quantitative characters (the production capacity and the content of raw protein in the grain), involves the "per se" previous analysis of the inbred lines for the characters studied; on the basis of this analysis, the best lines are included in a diallel system, that establishes the direction of the reciprocity effects.
The knowledge of the direction of the reciprocity effects for both characters is possible only by analysing the direct and reciprocal hybrids.
In this work there 8 inbred maize lines have been used, which were crossed in a [n(n-1)] diallel system. Fifty-six direct and reciprocal hybrid combinations have been obtained.
Knowing the grain yield and the percentage of raw protein in the grain for the 8 parental forms (Table 1), the reciprocity effects for the 2 characters in the 28 pairs of inbred lines have been determined and analysed.
Table 1. The grain yield and the content of raw protein
|Genotype||Grain yield(q/ha)||% raw protein|
The results obtained show that there are significant differences between the direct hybrids and the reciprocal ones regarding the grain yield and the content of raw protein in the grain.
Concerning the grain yield, the reciprocity effects have statistical significance thresholds for 9 pairs of inbred lines (Lc 257 and Lc 402; Lc 257 and Lc 403; Lc 257 and Lc 407; Lc 402 and Lc 407; Lc 403 and Lc 404; Lc 403 and Lc406; Lc 403 and Lc 407; Lc 403 and Lc3/Dxx; W153R and Lc3/Dxx) (Table 2).
Table 2. Reciprocity effects concerning the characters grain yield (x1)
and the content of raw protein in the grain (x2).
|Pairs of inbred lines (i. j) from hybrid combinations||X1 Grain yield (q/ha)||X2 % raw protein in the grain|
i x j
j x i
i x j
j x i
In the combinations studied, the inbred Lc 257 has the ability to transmit the production capacity character when it is used as female, but has no negative effects on the percentage of raw protein in the grain. The same thing is true of the lines Lc 402 and Lc 403 in the combinations Lc 402 and Lc 407; Lc 403 and Lc 406; Lc 403 and Lc 407; Lc 403 and Lc3/Dxx.
But in the combination Lc 403 x Lc 404, the line Lc 403, when used as a female, transmits to the descendent F1 both production capacity and the percentage of raw protein in the grain characters.
This aspect is more obvious for the inbred line W 153R, which in combination with line Lc 3/Dxx, transmits in the maternal form a production capacity very significant from a statistical point of view, and also transmits the percentage of raw protein in the grain character.
For this character (% raw protein in the grain), the negative reciprocity effects that turn up in most of the pairs of inbred lines suggest that the inversion of the parental forms would improve the percentage of raw protein in the grain in the descendant F1.
We could say that, for the set of analysed lines, the reciprocity effects were more frequent for the production capacity (grain yield) character, than for the procentage of raw protein in the grain.
For two or more characters that are going to be improved simultaneously we can infer the necessity of preservation of the reciprocity effects in a positive direction for all the characters. In our case, this fact is obvious for the pairs of lines Lc 403 and Lc404; W 153R and Lc3/Dxx.
The existence of some positive effects of reciprocity that are simultaneous
for the production capacity and the percentage of raw protein in the grain
characters permits us to obtain some maize cultivars that are able to join
harmoniously the two characters in the same genotype.
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