Elimination of yam mosaic virus from yam using an optimized combination of meristem culture and thermotherapy

Vegetatively propagated plants like yam are prone to yield losses by viruses as infection tends to build up in successive cycles of propagation. This study aimed to eliminate yam mosaic virus (YMV) from yam using an optimized combination of thermotherapy and meristem culture. A protocol was optimized for shoot initiation, multiplication, and rooting from shoots of four yam varieties using Murashige and Skoog (MS) medium with growth regulators. A control at 26 ℃ and a thermo-treatment at 36, and 40 ℃ followed by meristem culture was used to eliminate YMV and verified using double antibody sandwich ELISA (DAS-ELISA) and reverse transcription (RT)-PCR. Results showed that the highest explant initiation rate of 87.5% and 83.3% were obtained for variety Bulcha and Aw/Ar/005, respectively, on MS medium with 1.0 mg/L 6-benzylaminopurine (BAP) + 0.5 mg/L naphthaleneacetic acid (NAA). While the MS medium with BAP (0.5 mg/L) + NAA (0.25 mg/L) produced the highest initiation rate of 91.7% in variety Aw/Ar/001. The longest mean shoot length of 9.0 ± 0.37 cm was recorded in Bulcha on MS medium with BAP (0.5 mg/L) + NAA (0.25 mg/L). The highest percentage of rooting was obtained on MS medium with 1.5 mg/L indole-3-butyric acid (IBA) + 0.5 mg/L NAA for variety Bulcha and variety Aw/Wo/011. The maximum YMV elimination (93.3–100.0%) was noted at 40 ˚C thermo-treatment for 20 days followed by meristem culture. No amplification of the 586 bp fragment of YMV was obtained by RT-PCR in all the plants that went through 40 ˚C thermotherapy. The results make significant contribution in improving yam production in many countries, particularly in Africa where YMV is a significant constraint.