A Novel Type of Hybridity in Fragaria.

In 1930 I described briefly a case of hybridity in which apparently there had been a union between an egg cell of Fragaria vesca L. (n = 7) from Hawaii and a single genom (n=7) of Fragaria virginiana Duchesne (n=28) from the eastern part of the United States. The variety of F . vesca used as the female parent had white fruit. This plant was isolated in a room containing no other plants and was pollinated with pollen from a plant of F . virginium having red fruit. Several hybrids were obtained having 35 chromosomes. They resembled F. virginium. One plant only was found which had 14 chromosomes. Any strawberry specialist would have said that it was a plant of F. vesca, for it had all the major characteristics of this species. (In my preliminary paper, I stated that this plant resembled F. vesca in every respect, and then contradicted myself by saying that it showed “several other characteristics of F. virginiana.” The phrase was “minor characteristics” in the manuscript, but the word “minor” was left out by mistake. I had not, at that time, noted the margin difference in the middle leaflet.) The differences noted were red fruits (not a specific distinction), rootstocks slightly stouter, and leaflets slightly firmer and darker in color (as in F. virginiana) but not beyond the limits of variation of other varieties of F. vesca. It was also found that the center leaflet was dentate only halfway to the petiolule-as is characteristic of the variety of F. virginiana used-instead of being dentate for threefourths of the distance, as in the maternal variety. The phenomenon was interpreted as above. It was thought to be similar to the “maternal,” but red-fruited, type discovered by MILLARDET (1894) after an attempt to cross a white-fruited F. vesca with pollen from a redfruited F. chiloensis. Later, i t occurred to me that since the plant of F. virginiana which furnished the pollen had not been isolated, as was the mother plant, and since there were a few red-fruited plants of F. vesca in flower in another part of the greenhouse, there was a remote possibility that the plant in question was the result of crossing two varieties of F . vesca. During the past four years, the original plant has been studied carefully, together with numerous clones. In addition, the behavior of 18 Fz plants has been investigated. From the evidence thus obtained, there is little room to doubt the correctness of the original interpretation.