Micropropagation of Ageratum houstonianum by nodal segments

Ageratum houstonianum is a bedding and flowering potted plant originated from Central America which is generally propagate by seed. In this report a preliminary in vitro technique for propagation of A. houstonianum was investigated. In vitro germinated seeds were used to establish aseptic shoot cultures of several clones. Seedling stem segments bearing 3-4 nodes were placed on Murashige and Skoog (MS) basal medium plus 20 g L-1 sucrose, 8.0 g L-1 Agar to induce axillary shoot development. Axillary shoots were subcultured into the same medium and nodal segments were sectioned and subcultured to increase the stock of shoot cultures. Shoot cultures of the selected clone AG14 were used to accomplish in vitro propagation experiments. The MS medium, augmented with different concentrations of N-6-benzyladenine (BA) (0, 0.88, 1.78, 3.55, or 7.1 μM) either singly or in combination with indole-3-acetic acid (IAA) at 5.7 μM, as potential medium for shoot multiplication by single node segments was tested. The highest rate of axillary shoot proliferation was induced on the medium supplemented with 7.1 μM BA. Explants were divided, subcultured and continued to proliferate shoots. A proliferation rate of 5.2 shoots per single node explants every four weeks occurred. The highest number of node per axillary shoots after 8 week culture (4.5 nodes) was obtained in the medium with 0.88 μM BA and 5.7 μM IAA. The elongated axillary shoots could be in turn sectioned and subcultured to form an elongated stem again. Five IAA concentrations (0, 1.14, 2.28, 4.57, 5.71 μM) were tested to determine the optimum conditions for in vitro rooting of microshoots. The highest number of roots per microshoots was obtained with IAA at 2.28 μM. Ninety percent of the in vitro rooted plantlets were successfully established in soil. This micropropagation system of A. houstonianum based on axillary shoot development from nodal segments, followed by in vitro rooting, might be used for rapid and efficient mass propagation of improved selections and disease-free germplasm.