In vitro regeneration and micro-propagation of enset from Southwestern Ethiopia

Three clones of enset (Ensete ventricosum Welw. Cheesman) from southwestern Ethiopia (Keffa-Shaka zone) were investigated for their potential for micropropagation and regeneration in tissue culture. Corm and leaf tissue of greenhouse-grown plants as well as in vitro germinated zygotic embryos were used as starting material for micro-propagation and regeneration studies. Embryos were excised from disinfected seeds and cultured in vitro. Multiple shoots from both corm- and embryo-explants were obtained using regeneration medium supplemented with 10 μM or 20 μM BAP. Rooting of shoots was achieved using medium with 5 μM IBA, 1 μM BAP and 1 g l⁻¹ activated charcoal. Plantlets obtained by this process were transferred to soil under greenhouse conditions. Optimal conditions, which were determined for clonal propagation of three different genotypes of enset, allowing both in vitro micropropagation and regeneration, are described. This protocol makes for conservation of enset clones, rapid propagation of selected disease-free germplasm and more efficient breeding procedures. This revised version was published online in June 2006 with corrections to the Cover Date.     

Molecular characterization of a new badnavirus associated with streak symptoms on enset (Ensete ventricosum,Musaceae)

Electron microscopy of leaf samples displaying streak symptoms from enset (Ensete ventricosum), a banana‐like plant widely cultivated in Ethiopia, showed the presence of bacilliform shaped virions as known for badnaviruses. DNA extracts subjected to rolling circle amplification (RCA), polymerase chain reaction (PCR) and cloning and sequence analysis revealed that the virus has a circular double‐stranded DNA genome of 7,163 nucleotides encoding predicted proteins of 21.5 kDa, 14.5 kDa and 202.5 kDa, a genome organization known for badnaviruses. The virus is phylogenetically most closely related to Sugarcane bacilliform Guadeloupe D virus with a nucleotide sequence identity of 77.2% at the conserved RT/RNase‐H region and 73.6% for the whole genome. Following the current species demarcation criteria, the virus should be considered as an isolate of a new species in the genus Badnavirus for which the name Enset leaf streak virus (ELSV) is suggested. Leaf samples from enset and banana were screened using virus‐specific primers, and ELSV was detected in six of 40 enset but not found in any of 61 banana samples. On the other hand, Banana streak OL virus (BSOLV) was detected from the majority (60%) of symptomatic banana samples but not from enset samples. This paper reports the first full‐genome sequence of a putative new badnavirus species infecting plants in the genus Ensete. In addition, this is the first report of the occurrence of BSOLV in Ethiopia.