Chokecherry (Prunus viginiana L.) is an important shrubby species for agroforestry planting in the northern Great Plains states. The X-disease is a serious limiting factor for its utilization. The objective of this research was to produce clonal materials for studying the host and X-disease phytoplasma interactions and for screening X-disease resistant chokecherry germplasms. Shoot tips of 1–2 cm in length were isolated from 1-year old seedling plants, sterilized, and initiated on three basal media supplemented with 5 μm BA and 5 μm IBA. After five weeks, an average of 4.8, 2.2 and 0.3 new shoots were produced on Murashige and Skoog (MS) medium, woody plant medium (WPM) and Knop's medium, respectively. The newly formed shoots were subcultured on MS medium with 5 m BA and 5 m IBA. MS and DKW media gave significantly higher proliferation rates (12–13 shoots after 4 weeks) than WPM (5.5 shoots). Microshoots rooted in half-strength MS medium supplemented with 5 and 10 μm of either IBA or NAA. The shoots were either placed on the medium for 19 days, or for 5 days then transferred to a hormone free medium for 14 days. On the media with IBA, 80% to 90% of the microshoots rooted with an average of 2.4 roots per shoot and there were no differences in rooting percentage and root number. When shoots were exposed to NAA for 5 days, 66.7% of shoots on medium with 5 μm NAA, and 83.3% on the medium with 10 m NAA formed an average of 2.2 roots per shoot; but when the shoots were exposed to NAA for 19 days, 36.4% of shoots on the medium with 5 m NAA and 30% on the medium with 10 μm of NAA formed an average of 0.53 roots per shoot. These rooted shoots are under acclimation to the ambient environment.
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