Assessment of Genetic Variability Induced by Chemical Mutagenesis in Elite Maize Germplasm via SSR Markers

摘要

A breeding program, aimed at utilizing chemical mutagenesis and mutation breeding for induction of additional genetic variation in well-known elite maize (Zea mays L.) lines and hybrids, has been conducted in Bulgaria since 1973. The phenotypic variation created by chemically induced mutagenesis included important quantitative traits, such as grain yield, high protein content, reduced flowering time, changes in grain type, improved general (GCA) and specific combining ability (SCA) as well as improved abiotic stress tolerance. Twelve mutant lines obtained by chemical mutagenesis, followed by recurrent reciprocal mutation breeding (RRMB), and their initial lines Oh43, Oh40b, C103, B37, and a Pioneer brand hybrid 3737, were assessed for the induced genetic variability using 18 SSR markers. The mutant inbred lines, chosen because of their improved GCA and SCA for grain yield and proven predominance in Bulgarian breeding programs, showed shifts in their flowering time as compared with the initial inbreds. The SSR markers discriminated between the initial classical breeding inbred lines and the mutant inbreds that resulted from them. The level of the genetic diversity in the population of mutant inbreds with improved agronomic characteristics (0.651) was higher than that of classical inbreds (0.608). This indicates that chemical mutagenesis is a valuable tool for creating genetic variation in modern maize breeding programs for yield improvement and stress tolerance.