Explant initiation date and BA concentration influence shoot proliferation in vitro of two Liatris interspecific hybrids

Shoot proliferation cultures were established in vitro using flower-stem explants from two different interspecific hybrid plants of Liatris. Explants taken on two dates from field-grown plants were successfully established and axillary shoot growth promoted on a medium consisting of Murashige and Skoog basal salts and vitamins with 30 g·L^-1 sucrose, 1.0 μM BA, and 7.0 g·L^-1 agar, with a medium pH = 5.7. Initial explant contamination rates were significantly higher among expiants collected later in the growing season. Addition of BA (1.0, 2.0, 4.0, 8.0, or 16.0 μM) improved shoot formation compared to the control for both plants. Proliferation rates differed between the dates of establishment, the plants, and the BA treatments. Shoots rooted readily in medium without PGRs or with 1.0, 2.0, 4.0, or 8.0 μM K-IBA. Overall rooting was 88%. About 90% of the plants rooted in the presence of 1.0 μM K-IBA were successfully established in the greenhouse. Chemical names used: 6-benzyl adenine (BA); potassium salt of indole-3-butyric acid (K-IBA).