Protocols for Micropropagation of Woody Trees and Fruits

280
S.J. MURCH ET AL.
environmental changes in the Pacific Islands are potential threats to indigenous
breadfruit germplasm. Breadfruit varieties are traditionally propagated vegetatively,
vegetatively, via root cuttings for transport, sharing of genetic resources and to
maintain genetic uniformity but potential problems with these traditional propagation
methods include low survival rates, microbial infections, and difficulties in modern
transport arising from international plant quarantine restrictions.
In vitro culture and micropropagation using meristem proliferation have proven
to be an effective method for conservation, propagation and distribution of a wide
variety of plant species. In recent years, tissue culture techniques have been applied
to the propagation of tree species related to breadfruit such as jackfruit (Amin &
Jaiswal, 1993), but the success with breadfruit cultivars has been slow and less than
desirable. Recently, we have developed efficient protocols for mass propagation
from axillary buds and controlled environment production of axenic plants for germ-
plasm distribution (Murch et al., 2007). This chapter provides a detailed account of
various steps involved in the culture, maintenance, and sustained production of
breadfruit germplasm.
2.1. Donor Breadfruit Materials
2. PROPAGATION PROTOCOLS
Two types of donor plants, mature and juvenile trees, from three breadfruit
(Artocarpus altilis) varieties (Maafala, Puou and Puupuu) were used in micropropagation
experiments. Plant material from mature trees was collected from the
germplasm collection at the Kahanu and McBryde gardens of the National Tropical
Botanical Garden, USA. Greenhouse-grown juvenile trees were obtained from the
first cycle of in vitro propagation of breadfruit accessions at the University of Guelph
(Guelph, ON, Canada).
2.2. Explant Preparation from Donor Trees for the Initiation of In Vitro Cultures
1. Collect the axillary shoots tips (terminal bud and 0.5–1.0 cm of wood
tissue) (Figure 1A) from donor trees.
2. Place the shoot tip explants in a 1L beaker and wash thoroughly with
running tap water.
3. Surface sterilization of the explants is carried out in a flow laminar flow
bench.
4. Place the explants in 70% ethanol for 1 min.
5. Replace ethanol with 10% bleach (5.25% sodium hypochlorite) and
incubate for 15 min with occasional swirling of the explants for uniform
exposure to the sterilant.
6. Wash the explants 3–5 times with sterile distilled water.