Somaclonal variation in high tannin sorghums

Summary Genetic variants were found among over 6,000 primary plants (R₁) regenerated from embryogenic tissue cultures of eight high tannin sorghums Sorghum bicolor (L.) Moench]. Field assessment of somaclonal variation has progressed to the R₂ population, with over 48,000 R₂ seedlings (27,000 plants) in 1,126 rows from 1,055 R₁ plants. A total of 43 variant phenotypes was recovered, including several types of chlorophyll deficiencies, dwarfism, short culm, sterility, narrow leaf, and several previously unreported variants, such as ragged leaf, multibranched heads, and Hydra, a developmental variant which produces large numbers of panicles. Variation production greatly depends on parent genotype and appears to increase with increasing time in cultures. The toal average somaclonal variation rate (based per 100 R₁ plants) and somaclonal variant frequency (based per 100 R₂ plants) estimated in the tested population were 11.3 and 1.6, respectively. Chimerism was found in regenerants. The estimated size of the mutated sector carried by mutant regenerants ranged from the whole plant to less than 3% of a single head. The average proportion of mutated R₁ heads carrying large (80%–100%), medium (40%–80%), and small (<40%) mutated sectors was 38.7%, 26.0% and 35.3%, respectively. Some sector mutations do not appear until the R₃ generation. In order to avoid losing variants, the population for selecting somaclonal variation should be as large as possible. Some of these variants found may be useful for further study or for use in breeding programs.