Genética de Coffea. XXIII - Interação dos fatôres "sépalas desenvolvidas" e "calycanthema", em Coffea arábica

Abstract

The calyx of Coffea arabica flowers is usually reduced to five small scales. Exceptions are found in a few mutants, such as "calycanthema" and "goiaba". In the former the flower has a large and petaloid calyx while in the "goiaba" mutant the calyx has five developed and persistant sepals. Both mutants seem to derive from the typica variety (Coffea arabica, L. var. typica Cramer J by single independent mutations. The characteristics of the "calycanthema" are controlled by one main pair of genetic factoi's Cc. So far it has not been possible to secure homozygous CC plants, for when the corolla of "calycanthema" (Cc) dries after pollination, the whole flower, including the ovary, drops from the branch. The pollen is viable. "Goiaba" plants are homozygous for the main pair of factors sdsd, the heterozygous having sepals of intermediate size. The interaction between "calycanthema" and "developed sepals" has been determined. By crossing homozygous "goiaba" plants (sdsd) to heterozygous "calycanthema" plants (Cc), 50% "calycanthema" plants (SdsdCc) and 50% heterozygous "goiaba" plants (Sdsdcc) have been encountered. Crosses were also made between plants of Sdsdcc and SdsdCc constitutions. Five phenotypically "calycanthema" plants from F1 progeny were then crossed to normal individuals (SdSdcc) and two of them gave progenies with 50% "calycanthema" and 50% heterozygous for "developed sepals", indicating that these two plants had the genetic constitution sdsdCc, although their phenotype was that of "calycanthema". According to the definition proposed by Hollander, therefore, it may be said that "calycanthema" (C) is epistatic to "goiaba" (sd). Taking the typica variety as a standard it is evident, in this case, "the masking of the phenotype of one mutant or non standard allele (sd) by the phenotype of another mutant (C), also non standard and not allele".