On the genetics of tetraploid plants in Primula sinensis

Abstract

The purpose of this paper is to describe certain peculiar results obtained in the genetics of two “giant” races of Primula sinensis . Cytological investigation has shown these giants, unlike the giant races already described,* to be in the tetraploid condition, that is to say, that whereas in ordinary Primulas the chromosomes are x (12) in the gametic and 2 x (24) in the somatic stage, in the tetraploid giants the chromosomes are 2 x (24) in the gametic and, as nearly as can be counted, 4 x (48) in the somatic cells. Nilsson-Ehle and East have shown that factors of similar property may be reduplicated in the same zygote (or gamete), with various peculiar numerical consequences not otherwise intelligible, notably the appearance in certain F 2 -families of such ratios as 15D : 1R, 63D : 1R, and so on, when in the ordinary case 3:1 would be expected. The occurrences to be described in part recall this phenomenon ; but, as will be seen, they are accompanied by others at first sight entirely paradoxical (as, for example, the fact that the ostensible recessive may throw the dominant), and the whole series may be regarded as of special significance in view of the association with the doubled condition of the cell-constituents. Moreover, in the tetraploid Primulas, the reduplication affects not merely the factors for isolated characters, but extends simultaneously to the factors for all the characters so far investigated.