How to Establish and Manage a Clonal Bank

A clonal bank is a living collection of selected clones (asexually propagated plants) which are managed for breeding work. After a clonal test the best performer clones are retained (the “bad” ones are rogued), then pollarded to induce the production of juvenile shoots which are then vegetatively mass multiplied by rooting of cuttings. These rooted cuttings are used as propagules for clonal plantation development.

A major constraint in the use of vegetatively propagated planting stock is the apparent possibility that being uniform (genetically identical individuals) makes them more prone to pests, diseases and physiological disorders. As clonal plantations are considered long term investment it is necessary to protect them against diseases and pests by maximizing the genetic variability of the plantations, that is, their population. The population should have a wide genetic base or diversity. Experience from clonal plantation development indicated that great variability exists among clones in terms of growth, vigour (resistance against pests and diseases) and wood density (Campinhos, 1992 and Lal, 1993).

For planning purposes, in any planting year a single clone should be used only to ten percent of the area, that is, 10 superior select clones are required for the year. A clone also should be only used once in five years, such that, 50 clones selections are required (White, 1992). Hence, if a clone should be used only to 10 percent of the annual planting area and again only used once in five (5) years, then about 500 superior clones are required as sources of propagules for plantation development. Such degree of genetic variability could reduce the risk of attack of probable disease and insect damage. Concommittantly, the decision, on how many clones should be planted in the bank is reached after considering also the shoot productive capability of the clone, the success of rooting cuttings (it varies among clones), the survival rate/percent of the rooted cuttings in the field, and the annual planting target area.

How to establish a clonal bank

1. Select plus trees from a natural stand or from plantations or from the most adapted provenance trial plots.

2. Collect vegetative materials (twigs, branches) from those selected plus trees and grow them by either grafting, budding or rooting, whichever is most effective to obtain high success of establishment. Marcotting, if equally effective could be used to vegetatively reproduce the ortet. The number of ramets in each clone should not be less than 20.

3. Harden the ramets in the nursery for sufficient duration to allow them to fully develop before planting in the field.

4. Field lay-out. Clones shall be planted in pure lines. This means that, ramets from a clone should be planted within a row or line. To prepare the lines, place an identification tag on a one-meter tall stake, indicating the clone code number. Then put stakes at each planting spot within a line and dig planting holes threat. The distance between lines/clones is 5 meters and planting distance between ramets of the same clone (within line) is 3 meters. Be sure to sketch the lay-out on a map of the clone bank.

5. Planting out - When the ramets are sufficiently hardened, they should be planted in the site during the onset of the rainy season. Do not mix clones or ramets among clones. All ramets belonging to a clone must be planted on one line. Ensure that the locations of the clones are properly recorded/indicated on a map of the clone bank.

Roguing the clone bank

Since the clones are planted in lines, it is possible to compare them with ease in regard to their growth behavior, stem form and resistance or susceptibility to insects and diseases. This constitutes a clonal test which could run from one to six years (depending on the species). Then based on the result of this test, those clones (including ramets) which were found poor performers, with respect to the aforesaid, are rogued (removed) from the clone bank. These inferior clones, however, could be replaced by new selected clones.

Multiplication of juvenile shoots

The ramets should be pollarded after the clonal test to induce the production of more juvenile shoots. Then to mass multiply them, cuttings from these juvenile shoots are rooted in a mist propagation unit using standardized propagation procedures. Properly graded rooted cuttings are then utilized for the development of clonal plantation.

Maintenance of the clonal bank

Regular pruning of the ramets is required to remove old branches and also to induce continuous production of juvenile shoots. Apply commercial fertilizer rich in nitrogen or organic fertilizer to the clones. This practice will induce the production of more vegetative parts in addition to maintaining the general health of the clones.

Clonal Multiplication Area

Another means of ensuring the production of juvenile materials for mass multiplication is to establish a clonal multiplication area.

In Eucalyptus (Campinhos and Ikemeri, 1983 and Lal, 1993) the selected mother trees in the plantation are felled above ground level (about 12 cm) and coppices are allowed to grow on the stump. Then 45–55 days old coppices are harvested, transformed into stem cuttings for rooting and transplanted in a clonal multiplication area (this area is usually situated near the major mist propagation facilities and nursery). At every 40 to 45 days, thereafter, coppices are harvested from this multiplication area, transformed into stem cuttings for rooting in root trainers placed inside a mist propagation unit. The rooted cuttings are kept for five weeks in the shade house into an adjacent open area for further hardening for a period of 2–3 weeks before outplanting.

The ratio of clonal multiplication area to area of planting is 1:100. In other words, to plant 100 hectares you need one hectare of clonal multiplication area, bearing in mind that number of plants per hectare of clonal multiplication area is the same as that for the commercial planting area.

Literature Cited

1. Campinhos, E. Jr. and Y. K. Ikemori. 1983 Production of vegetative propagules of Eucalyptus spp. by rooting of cuttings. Paper presented at the "Second Symposium on Plantation Forest in the Neotropics - Its Role as Source of Energy, IUFRO S1.07.09. Viscose. 6–13 February 1993.

2. Campinhos, E. Jr. 1992 A Brazilian example of forestry plantation in tropical region; Aracruz. Paper presented at the Regional Symposium on Recent Advances in Mass Clonal Multiplication of Forest Trees for Plantation Programme. Cisarua, Bogor, Indonesia, 1–8 December 1992. FORTIP (RAS/91/004).

3. Darus Ahmad D. 1992 Rooting cuttings of dipterocarps under automatic mist spray. As observed by and explained to N.Q. Zabala during his visit to the Forest Research Institute of Malaysia on 17 March 1992.

4. Halle, F. and H. Kamil. 1981 Vegetative propagation of dipterocarps by stem cuttings and air-layering. Malaysian Forester 44(2–3): 314–318.

5. Lal, P. 1993 Eucalyptus improvements at ITC Bhadrachalam Paperboards Ltd. Paper read at the Workshop on Production of Genetically Improved Planting Material for Afforestation Programmes. Sponsored by ICFRE and FORTIP (RAS/91/004). Institute of Forest Genetics and Tree Breeding, Coimbatore, India. 18–25 May 1993.

6. Masano. 1992 Rooting cuttings of Shorea leprosula and S. selanica at the Forestry Research and Development Center (FRDC), Bogor, Indonesia, as observed by N.Q. Zabala on a visit to FRDC, Bogor on 10 March 1992.

7. Momose, Y. 1978 Vegetative propagation of Malaysian Trees. Malaysian Forester 41(3): 219–223.

8. Paler, R.R. and Q.Z. Alcober Jr. 1991 Preliminary results on rooting of cuttings of almon, red lauan, mayapis, tangile, apitong and white lauan. The Philippine Lumberman. Sept. – Oct. 1991.

9. Smits, W.F.M. and I. Yasman. 1991 Vegetative propagation by rooting cuttings of some dipterocarp species using bubble bath method (hydroponics system) as explained to and observed by N.Q. Zabala on a visit to Tropenbos-Kalimantan Project, Wanariset Research Station, East Kalimantan. Indonesia on 13–14 March 1991.

10. Srivastava, P.B.L. and P. Manggil. 1991 Vegetative propagation of some dipterocarps by cuttings. Malaysian Forester 44(2:3):301–312.

11. White, K. 1992 Small scale vegetative multiplication of Eucalyptus and its use in clonal plantations. Paper read at the Regional Symposium on Recent Advances in Mass Clonal Multiplication of Forest Trees in Plantation Programmes. FORTIP (RAS/91/004). Cisarua, Bogor, Indonesia, 1–8 December 1992.

About Our Project

The UNDP/FAO Project on Improved Productivity of Man-Made Forest Through the Application of Technological Advances in Tree Breeding and Propagation, abbreviated FORTIP (Forest Tree Improvement Project) is a regional project on tree breeding and propagation. It covers 10 countries, viz. Bangladesh, Bhutan, India, Indonesia, Malaysia, Nepal, Pakistan, Philippines, Sri Lanka and Thailand.

The development objective of our Project is to help stem deforestation and resulting environmental degradation through the establishment of more productive and well adapted plantations.

The Project is supporting the on-going national Research & Development activities in the participating countries to promote the use of genetically superior seeds and propagules in their tree planting programmes, which will ultimately lead to more productive plantations.

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