Protocols for Micropropagation of Woody Trees and Fruits

CHAPTER 6
ORGANOGENESIS AND CRYOPRESERVATION
OF JUVENILE RADIATA PINE
C. HARGREAVES AND M. MENZIES
Ensis, Private Bag 3020, Rotorua, New Zealand
cathy.hargreaves@ensisjv.com
mike.menzies@ensisjv.com
1. INTRODUCTION
New Zealand has 1.81 million hectares of plantation forests and 89% of this is
radiata pine (Pinus radiata D. Don) (Ministry of Agriculture and Forestry 2006).
Initial stocking rates vary but are typically in the range of 800–1100 plants per
hectare. New planting and replanting of harvested areas was about 50,200 ha in
2004 (Ministry of Agriculture and Forestry 2006), requiring around 50 million
nursery plants.
Sufficient open- and control-pollinated seed-orchard seed is produced for
New Zealand requirements. The more expensive control-pollinated seed is used to
improve genetic gain, and this has led to greater use of vegetative propagation by
cuttings and tissue culture to provide more than 25% of current planting stock
(Menzies et al., 2001). Tissue culture methods developed to amplify control-pollinated
seed include organogenic methodologies (Reilly & Washer, 1977; Aitken et al.,
1981; Horgan & Aitken, 1981; Smith et al., 1982) and somatic embryogenesis from
immature zygotic embryos (Smith et al., 1994; Smith, 1996, 1997).
From control-pollinated seed, selections may also be made of outstanding individuals
that can then be propagated and tested as clones. Clones from within top
families have demonstrated marked improvements in performance when compared
with family averages (Johnson, 1988). However, propagules generated clonally from
mature radiata pine (more than 4 years old) have a lower initial growth rate than
those from younger material (Menzies & Klomp, 1988). Conversely, many
characteristics of commercial interest, such as wood properties and resistance to
some diseases, can be identified only when trees are 8 to 12 years old. Therefore, at
an age by when elite trees can be identified, they are mature and clonal propagules
exhibit reduced growth rate. Options to maintain juvenile propagules while field
testing takes place include cool storage of in-vitro grown shoots (Aitken-Christie &
Singh, 1987; Horgan et al., 1997) and maintenance of stool beds in the nursery
51
S.M. Jain and H. Häggman (eds.), Protocols for Micropropagation of Woody Trees and Fruits, 51–65.
© 2007 Springer.