Rubber Tree Clonal Plantations: Grafted vs Self-Rooted Plant Material

Abstract

The forest tree species Hevea brasiliensis is extensively planted in the humid tropics to meet the increasing demand for natural rubber. Huge quantities of planting stock are therefore needed. The seed option remains the easiest and cheapest way to establish plantations of rubber trees but those show a great variability for vigor and also for latex yield. The rationale of produ- cing clones for overcoming this variability was already obvious in the early 1910’s but due to the difficulties encountered at that time for rooting shoots, grafting was used as an alternative cloning method. The striking increase in yield noticed from the graft-derived clonal plantations warranted their large scale development. Eventually, the budded clones by virtue of their much higher and uniform produc- tivity supplanted the seedlings in most industrial plantations. However, grafting is also associated with drawbacks and for decades efforts aiming at mass producing selected rubber tree clones on their own roots by rooted cuttings have been pur- sued. However, this approach was pro- gressively abandoned due to disappoin- ting rooting results and, from the 70’s onwards, priority has been given to in vitro methods which were booming during this period. But despite 40 years of heavy investments, industrial H. brasiliensis clones could still not be mass micropro- pagated in vitro efficiently enough to meet the requirements of large scale produc- tion. The situation may change radically soon, however, due to the development of new nursery techniques adapted to the mass clonal production by rooted cuttings of any H. brasiliensis selected genotype. Efforts to improve the techniques as well as the establishment of new field trials are underway in order to determine if self-rooted rubber tree clones are more productive than grafted ones. This old issue is becoming of overriding impor- tance considering the increasing pres- sure on land availability reducing thereby the prospects for expanding rubber tree plantations.

Natural rubber and climate change: a policy paper

“…Eventually, budded clones supplanted seedlings in most large-scale plantations. Large companies restricted the use of seedlings for rootstock production, whereas seed-derived rubber trees for latex production, or "jungle rubber", have been mostly used by smallholders (Webster 1989;Cardinal et al 2007;Masson and Monteuuis 2017).…”

True-to-type micropropagated plants of para rubber (Hevea brasiliensis Müll. Arg.) via somatic embryogenesis

“…Microcutting (Kalawong et al, 2014) and nodal segment micropropagation (Sirisom and Te-chato, 2014) via in vitro culture are the other alternatives. However, the vegetatively propagated plants lack taproot system, which makes it susceptible to wind disasters (Masson et al, 2013;Masson and Monteuuis, 2017). Somatic embryogenesis may overcome this problem, as it produces large number of plantlets containing tap root system, similar to the seedlings produced by seed germination (Zhao et al, 2015;Rahman et al, 2017;Wang et al, 2017).…”

Histology and induction of rooting in rubber tree cuttings (Hevea brasiliensis (Willd. Ex A.Juss.) Müll.Arg.)

“…To supply the global demand, currently, the production is formed mainly by the grafting system, of the budding type (Borelli, 2016). Unselected seeds are used in the rootstock and in six months the seedlings are ready to receive the portion of the scion, responsible for the bleeding, and provided with selected hybrids (Masson and Monteuuis, 2017). The grafted seedlings are suitable for planting in about 24 to 48 months (Peres-Junior, 2019).…”

“…Parallel to production, research with other methods of vegetative propagation, such as cutting, was used (Castro et al, 1987). Starting in the 1970s, priority was given to in vitro methods that were booming at the time, but after years of investment, alternative techniques of rubber tree clones could not be propagated efficiently for commercial scale (Masson and Monteuuis, 2017). Although numerous researches have been conducted (Alves et al, 2019;Antwi-Wiredu et al, 2018;Cardoso, 1961;Lemos-Filho et al, 1994;Masson and Monteuuis, 2017;Medrado et al, 2000;Muzik, 1953;Muzik and Cruzado, 1958;Muzik and Cruzado,1956), few published studies have achieved rooting success, however, none of them used the combination of techniques tested in our study (Castro et al, 1987;Medrado et al, 1995;Mendes, 1959;Monteiro et al, 2015;Silva et al, 2020;Vallejos-Torres et al, 2021).…”