• W. Black

      Articles written in Journal of Genetics

    • Studies on the inheritance of tuber colour in potatoes

      W. Black

      More Details Abstract Fulltext PDF

      The five factors and their relationships, used in the above explanation of tuber colour inheritance, may be summarised as follows:

      D, a basic factor incapable of producing pigment alone.

      R, a red-colour-producing factor incapable of producing colour alone, but giving a red coloration in the presence ofD.

      H, an inhibitor, which, when heterozygous is incompletely dominant to eitherD orR when one of them is homozygous; or, when homozygous, is incompletely dominant when bothD andR are homozygous.

      P, a blue-colour-producing factor which functions only in the presence of bothD andR and reacts to the presence ofD andH in a manner similar toR.

      B, a second blue-colour-producing factor which in effect is similar to the factorP.

    • Studies on the inheritance of resistance to wart disease (Synchytrium endobioticum (Schilb.) Perc.) in potatoes

      W. Black

      More Details Abstract Fulltext PDF

      It is concluded that there are various kinds of resistant varieties as illustrated by differences in toleration and reaction towards the fungus. Similarly, there are various kinds of susceptible varieties: these differences are due to physiological qualities in the plant which in turn are controlled by definite hereditary factors.

      The inheritance of resistance to wart disease is dependent upon the cumulative interaction of three factors inducing resistance. The three factors are designatedA, B, andC, and each is given a value, viz.A=1,B=2, andC=3, which represents approximately the relative power of the factorial contributions towards resistance. In any particular plant the sum of the values must be seven or over to induce sufficient resistance to overcome infection under cultural conditions, and consequently the presence of at least two factors is required. The numerical values assigned to genotypes correspond to phenotypic reaction in such a manner that the higher the value, the more resistant is the phenotype.

      The writer desires to express his indebtedness to Mr Thomas Anderson, M.A., B.Sc., Director of the Seed Testing Station, Department of Agriculture for Scotland, for advice and criticism and for providing facilities for study.

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