Genetic and Cytogenetic Variation in Plants Regenerated from Organogenic and Friable, Embryogenic Tissue Cultures of Maize

Abstract

Recent advances in maize(Zea mays L.) tissue culture methods permit reproducible establishment of rapid‐growing, friable, embryogenic (Type‐II) cultures from some genotypes. Although Type‐II cultures have replaced the more common Type‐I (relatively compact, organogenic) cultures for many applications, little information is available concerning somaclonal variation in plants regenerated from Type‐II cultures. This study was conducted to determine the relative frequency of genetic and cytogenetic variants in plants regenerated from Type‐I compared to Type‐II maize tissue cultures. Type‐I and Type‐II cultures were initiated from immature embryos of the inbred line A188, A188‐BC6 lines containing various genetic markers, and segregating progenies of an A188/B73 genetic background. Plants were regenerated 16 and 36 wk after culture initiation and were analyzed for pollen sterility, cytological abnormalities, and phenotypic variants in progeny generations. After 16 wk in culture, 33.3 and 20.8% of the regenerants from Type‐II and Type‐I cultures, respectively, possessed at least one abnormality. These values increased to 37.2 (Type‐II) and 24.2% (Type‐I) after 36 wk in culture. As expected, the frequency of chimeric plants was lower from Type‐II than from Type‐I cultures: however, culture age had a larger effect on the frequency of chimeric plants than culture type. Although reduced compared to Type‐I cultures, the frequency of chimerism in regenerants from Type‐II cultures was still quite high, ranging from 9.4 to 50.0% of the variant regenerants. The results demonstrate that genetic and cytogenetic abnormalities are frequently recovered in plants regenerated from both organogenic and friable, embryogenic maize tissue cultures.