Nonreciprocal partial cross-incompatibility in maize

Abstract

A case of cross-incompatibility among crosses in our genetics nursery was first observed in 1975. These crosses though involving controlling elements in maize (Zea mays L.) do not necessarily implicate these elements. When the derivative genotypes from the genetic stocks were crossed by specific male parents, ears with reduced seed set (RSS) were produced. In the reciprocal cross where these same genetic stocks were used as the male parent, ears with normal seed set (NSS) were obtained. The RSS effect is a heritable character caused by an incompatibility interaction between the female tissue and a specific pollen type. The genetic control of the incompatibility interaction has been hypothesized to be influenced by a cytoplasmic–chromosomal interaction in the female and a chromosomal factor in the pollen. The site of the incompatibility interaction is not on the silk surface because the incompatible pollen germinated and developed normally on the silk surface. Thus, the incompatibility interaction can occur either inside the silk or the ovule.