Inheritance of "decussate" character: Differences between the offspring from reciprocal crosses

In previous publications we described the phenotype of "decussate" plants (1967, M. Blanco et al., IV Jornadas de Genética Luso - Espanholas. Itto. Gulbenkian de Ciencias, Oeiras, Portugal, pgs. 41-44). Here we compare segregations in progenies resulting from reciprocal crosses of the same stocks. All the progenies studied resulted from crossing one inbred, A (homozygosis 87.5%), with another inbred, B (homozygosis 75%). Each progeny had only two parent plants (both plants being "decussate"). In order to do comparisons, the progenies were classified into two groups (I and II). In group I, each "A" plant was crossed, in both directions, with another "B" plant. Therefore, from each pair of parent plants two progenies were obtained, Ai x Bi and Bi x Ai. From six such pairs of plants, twelve progenies were obtained. In order to compare the progenies A x B with the reciprocal ones, all the six progenies of each class were put together. In group II, fifteen progenies of inbred A crossed (as female parent) with inbred B are compared with 10 of inbred B crossed (as female parent) with inbred A. In this group II, the two parent plants of each cross A x B are not the same plants of each cross B x A. Here too, all progeny of the same class were put together.

The inbred A was a S2 from the cross of the inbred "a" (as female parent) with the "decussate" stock ("De"): Inbred A = (a x De) selfed twice. The inbred B was originated crossing the "decussate" stock (as female parent) with a "b" inbred; crossing again the resulting F1 (as female parent) with the "decussate" stock, and selfing the resulting backcross: Inbred B = [(De x b) x D] selfed.

Due to their respective pedigrees, the cytoplasms of A and B could be different. Because of this, we call the cytoplasm of A, "normal cytoplasm" and the cytoplasm of B, "decussate cytoplasm." The data and the levels of significance of chi-square test, for both groups of comparison, were as follows:
Group Cross Progenies Normal Decussate Chi-square
I A x B 6 79 37 13.63*
I B x A 6 28 43  
II A x B 15 219 48 71.15*
II B x A 10 51 77  

*p < 0.001

In group I and in group II, the progeny from female parents with "decussate" cytoplasm have a greater proportion of decussate plants than the corresponding reciprocals.

Mariano Blanco, Angel Alvarez, Luis Bosch and José L. Blanco

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

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