In vitro regeneration of disease free enset [Ensete ventricosum (Welw) Cheesman] planting materials from bacterial wilt diseased plants using shoot tip culture

Abstract

Enset is an important food crop produced in Ethiopia with great role in food security. The demand of the crop is increasing throughout the country. However, the production as a whole is decreasing due to devastation by enset bacterial wilt. The studies were conducted to develop the procedure for obtaining multiple disease free plantlets from infected enset plants. Shoot tip explants from infected suckers of three clones Arkiya, Digomerza and Mazia were cultured on MS media supplemented with different combinations of benzylaminopurine (BAP) and naphthaleneacetic acid (NAA) each with concentration of 0, 1.5, 3, 4.5 and 6 mg/L with 0, 0.5, 1, 1.5 and 2 mg/L, respectively. The effect of growth regulators on shoot growth parameters was examined. The minimum days (11.66) for multiple shoot induction were recorded for Mazia on media with 4.5 mg/L BAP and 1.5 m/L NAA. The maximum number of shoots (23.0) was also obtained for Mazia on the same hormone combination as for days of induction. Whereas, the maximum shoot length (8.1 cm) was recorded for Digomerza on media with 3 and 1 mg/L NAA. Similarly, for root induction and growth MS media with different concentrations of indulebutyric acid (IBA; 0, 0.5, 1, 1.5 and 2 mg/L) were evaluated. The minimum days (10.5) to root induction was observed for Mazia on media with 1.5 mg/L IBA and the maximum root number (3.8) was recorded at 2 mg/L IBA. In the efficiency of shoot tip culture for Xanthomonas pathogen elimination, sample suspension was prepared from shoots regenerated from diseased suckers and transferred on semiselective yeast peptone sucrose agar (YPSA) medium. The result of colony observation indicated that many microbes are living in enset saprophytically as mixed colony growth was observed within 24 h after sample culturing. Pathogenesity test on clean suckers of susceptible clone showed that the colonies grown were due to endophytic microbes since none of the colonies were capable to develop disease symptoms as sample of the pathogen strain.

Keywords: Ensete ventricosum, benzylaminopurine (BAP), indulebutyric acid (IBA), naphthaleneacetic acid (NAA), shoot tip, Xanthomonas, yeast peptone sucrose agar (YPSA)