The chromosome constitution of the pomoideæ

Abstract

Previous investigation on cultivated varieties of apples have shown that the apparent basic chromosome number is 17, but chromosome pairing, morphology and breeding results indicate that the 34 chromosome form a more complex constitution than that of an ordinary diploid. In a recent paper (Darlington and Moffett, 1930) it was concluded that in the cultivated apples the set of 34 chromosome in the diploid belong to seven types, three of which are represented six times and four them are represented four times. Thus the original ancestor of the apple would have had a basic number of 7, and the present number of 17 is a secondary basic number. The derived series of polyploids with chromosome numbers 34, 51 and 68 are, therefore, secondary polyploids.