The Interaction of Nuclear and Cytoplasmic Factors in the Inheritance of Male Sterility in Maize.

ALE sterility in plants is of unusual interest since its inheritance is due M to a number of different mechanisms. In the early days of genetics a controversy existed as to the relative importance of the nucleus and the cytoplasm in inheritance. Many investigators believed the nucleus was all-important and relegated the cytoplasm to a non-essential role. That the cytoplasm did not always play an indifferent role in heredity was shown by certain cases of male sterility which were strictly cytoplasmically determined and also by those male steriles resulting from interaction of specific genes and cytoplasm. Male steriles resulting solely from genic action are most common. EMERSON, BEADLE and FRASER (1935) list twenty different male sterility genes in maize. Gene-determined male steriles have been reported in tomata (CRANE 1915), potato (SALAMAN 1912), barley (SUNESON 1940), and sugar beets (OWEN 1945) as well as in a number of other plants (LEWIS 1941). BATESON and GAIRDNER (1921) described a male sterile condition in Linum where the phenotype of the Fz progeny depended upon the direction of the parental cross. When the procumbent race was used as the female parent in crosses with common tall flax, the F2 population segregated normal and male sterile individuals in a 3 : 1 ratio. However, the reciprocal cross yielded only normal progeny. CHITTENDEN and PELLEW (1927) and CHITTENDEN (1927) believed these results were due to an interaction between gene and cytoplasm. Plants are sterile only when they possess the cytoplasm of the procumbent race and are homozygous for a specific recessive gene normally found in common tall flax. This interpretation was later confirmed by GAIRDNER (1929). OWEN (1945) reported a case of male sterility in the sugar beet (Beta vulgaris) which also involved gene-cytoplasm interaction. Plants possessing the normal cytoplasm ( N ) were male fertile while plants with the sterile cytoplasm (S) were either fertile or sterile depending upon their genic constitution. OWEN showed that at least two genes influenced the degree of sterility. Plants with the S cytoplasm and homozygous recessive for both