Inheritance of Semi-Sterility in Maize

Abstract

(1) Reciprocal crosses between normal and semi sterile maize plants give equal numbers of normal and semi-sterile offspring. Self-pollination of semi-sterile individuals likewise produces the same two classes in the same proportion. (2) In explanation of these results it is suggested that a section of one chromosome carrying genes active in the Gallatin, or an entire chromosome, has become attached to a non-homologous member of the complement. The modified and normal chromosomes assort at random in the reduction divisions. Spores receiving the translocated section in duplicate or lacking it entirely abort. The other two classes are functional. (3) The existence of a new class of normal plants among the offspring of semi-sterile individuals has been definitely established. These plants, called x-normals, are fully fertile and give all semi-sterile when crossed with the original normal type. (4) If semi-sterility arises in a small proportion of the individuals in a population breeding at random the population will return quickly to its original condition. In a self-pollinated species, however, x-normal plants will become established and may eventually constitute 50 per cent. of the population, although attainment of this proportion is extremely slow after the first few generations.