Somaclonal variation in high tannin sorghums

Area of Science:

• Plant genetics
• Agricultural science
• Biotechnology

Background:

• Sorghum bicolor (L.) Moench is a vital crop, and understanding genetic variation is crucial for its improvement.
• Tissue culture regeneration can induce somaclonal variation, offering a source of novel genetic diversity.
• High tannin sorghums present unique challenges and opportunities for crop breeding.

Purpose of the Study:

• To investigate and characterize somaclonal variation in high tannin sorghum regenerated from embryogenic tissue cultures.
• To assess the frequency and types of genetic variants in subsequent generations (R1, R2, R3).
• To evaluate the potential utility of identified variants in sorghum breeding programs.

Main Methods:

• Regeneration of primary plants (R1) from embryogenic sorghum tissue cultures.
• Field assessment of somaclonal variation in over 48,000 R2 seedlings derived from 1,055 R1 plants.
• Phenotypic characterization of variant traits, including chlorophyll deficiencies, growth habits, and reproductive characteristics.
• Analysis of chimerism and mutation sector size in regenerants.

Main Results:

• Over 6,000 R1 plants revealed genetic variants.
• A total of 43 variant phenotypes were recovered in the R2 population, including novel traits like 'Hydra' (multiple panicles) and 'ragged leaf'.
• Variation frequency depended on parent genotype and culture duration, with average rates of 11.3% (R1) and 1.6% (R2).
• Chimerism was observed, with mutated sectors varying in size from entire plants to less than 3% of a head.
• Some mutations were only apparent in the R3 generation.

Conclusions:

• Somaclonal variation in sorghum is a significant source of genetic diversity, yielding both known and novel phenotypes.
• The frequency and type of variation are influenced by genetic background and in vitro culture duration.
• Identified variants, particularly novel ones, hold promise for future sorghum breeding and genetic research.
• Maximizing population size is essential for effective selection of somaclonal variants to avoid loss.