Protocol optimization for in vitro propagation of two Irish potato (Solanum tuberosum L.) varieties through lateral bud culture

Potato is a versatile vegetable that is eaten all around the year. The objective of this study was to establish a protocol for in vitro micropropagation of Gudene and Belete popular varieties in Ethiopia from lateral bud explants. For shoot induction and multiplication, lateral bud explants were cultured on MS basal medium supplemented with different concentration levels of PGRS. Rooting was done on the same media type with different concentration levels of IBA and NAA in combination. The rooted plantlets were then acclimatized under poly-house conditions by transplanting the plantlets regenerated on moist soil mixture of loam soil, sand and compost in 2:1:1 ratio respectively. Results showed that shoot initiation, shoot multiplication and root formation responses were significant (P<0.05) at different hormone levels and combinations. 91.67 and 87.5% of explants survived and initiated for Gudenie and Belete varieties, respectively on shoot initiation MS basal medium supplemented with combination of 2.0 mg/l BAP and 1.0 mg/l IAA. In both varieties, number of nodes/explant, number of shoots/explant and shoot length/explant were significantly (P<0.05) higher at 0.5 mg/l BAP and 2 mg/l Kn. Number of days to shoot emergence was also found to be shorter at this level of hormonal combination than other treatments. Number of roots/shoot, root length/shoot, root fresh and dry weight were significantly affected due to growth regulators combination. The acclimatization experiment showed that plantlets of both varieties survived better on the sterilized soil mixture (loam red soil, san and compost) in a ratio of 2:1:1 with better Gudene performance as compared to the second variety.   Key words: Explants, auxin, cytokinin, in vitro propagation, MS media and lateral buds.