Callus induction in three mosaic disease resistant cassava cultivars in Benin and genetic stability of the induced calli using simple sequence repeat (SSR) and sequence-characterized amplified region (SCAR) markers

The effect of different concentrations of thidiazuron (TDZ), benzyl amino purine (BAP), kinetin and 2,4-dichlorophenoxy acetic acid (2, 4-D) on callus induction in three elite cassava cultivars (agric-rouge, atinwewe and agblehoundo) was evaluated. Leaf explants harvested from greenhouse-grown cassava were sterilised using different concentrations of commercial bleach commonly called Jik (3.85% NaOCl) at different time intervals. The highest number (94%) of clean explants was obtained when 2% (v/v) Jik was used for 15 min. The explants were cultured in half MS media supplemented with different growth regulators TDZ, BAP, kinetin 2, 4-D, 100 mg/l myo inositol, 2% sucrose and gelled with 0.3% phytagel. Callus formation was observed from the cut edges of the leaves in all cultivars after 10 days in medium supplemented with TDZ, 12 days in BAP medium, and 15 days in kinetin medium. There were significant (p < 0.05) differences in callus formation among all cytokinins types and concentrations. However, there were no significant differences in callus formation in different 2,4-D concentrations. All 2,4-D concentrations produced 100% callus in all the cultivars. However, 2,4-D at 2 µM significantly produced the highest (2.48±0.30) callus weight in cultivar atinwewe. Furthermore, simple sequence repeats (SSR) and sequence-characterized amplified region of the induced calli on TDZ and 2,4-D media indicated the loss of CMD2 gene among induced calli compared to the mother plants.   Key words: Cassava, simple sequence repeats (SSR) and sequence-characterized amplified region (SCAR), genetic stability, callus, cytokinins, auxins.