RECONSTITUTION OF FRAGARIA X ANANASSA; THE EFFECT OF FRAGARIA VIRGINIANA CYTOPLASM

Crosses c x v always had normal stamen development and good pollen fertility as in F. chiloensis. The same results were observed in the F₂ and backcrosses, even after three backcrosses by F. virginiana. The reciprocal F₁, v x c, and F₂ progenies showed good fruit set but had variable stamens development and pollen fertility reduced to 0–49%. Both of these characteristics varied within and among plants. In backcrosses ((v x c) x c), male-sterile plants resulted when the mother plants were male-sterile. If the mother plants had up to 50% good pollen, the pollen fertility in the progenies were usually similar to that of the mother plant and varied from 0–50%. The male-sterile plants of ((v x c) x c) and further backcrosses by c showed different malformations of the stamens. This was displayed by transition stages of male to female organs. The anthers were reduced and white, sack-formed structures were observed on them which proved to be ovules. Finally, fully fertile-looking achenes were developed instead of stamens. There is strong evidence for a maternal, cytoplasmic effect of F. virginiana. Genes for male organs of F. chiloensis may be inactivated by the cytoplasm of F. virginiana. Even after four backcrosses of v x c by c, stamen development and pollen fertility were still repressed.

Download Adobe Acrobat Reader (free software to read PDF files)