Cytological Analysis of Seedling Roots, Transformed Root Cultures and Roots Regenerated from Callus of Swainsona galegifolia (Andr.) R. Br

The stability of chromosome number was investigated in cultures of roots from Swainsona galegifolia. Roots from germinated seeds or plants grown in vitro when cultured in liquid medium howed 90% or more cells with the diploid number of 2n = 32. The remaining cells showed aneuploidy mostly below 32. The stability of chromosome numbers was not affected by transformation with Agrobacterium rhizogenes although when roots were transformed with A. rhizogenes LB 9042 the range of chromosome numbers in the few aneuploid cells present was higher than in roots for which strain A4 was used. In contrast, roots regenerated from callus had only 1·5% of cells with 2n = 32 and showed a modal number of 18. Six root cultures established from individual roots regenerated from callus showed a wide variation in number (8–83). Five cultures had a modal number around 18, the sixth, a modal number of 39 which is above the diploid number. The implication of the results for the production of secondary metabolites from root culture is discussed.