Contribution to Natural Rubber Production without Exogenous Hormonal Stimulation

Abstract

Rubber production and especially its increase absolutely depend on the activation of the latex-producing metabolism. Can the latex-producing metabolism activation mechanism developed by rubber tree lead to higher yield without exogenous hormonal stimulation? In order to verify this decisive hypothesis, several works, carried out for nine years in Southern Côte d’Ivoire, were conducted on some 15 clones (IRCA 18, IRCA 209, IRCA 111, IRCA 130, PB 235, PB 260, PB 280, PB 330, PB 310; GT 1, BPM 24, RRIC 100; PB 217 and PR 107) of the three metabolisms respectively, active, moderate and slow, with two main statistical designs. On a small scale, in a “one-tree plot” design, the same latex harvesting system, tapping in d4 with different hormonal stimulation regimes (0/y; 2/y; 4/y; 6/y; 8/y; 13/y; 18/y; 26/y, 39/y and 78/y), has been applied to all treatments. In a randomized complete block design, different tapping frequencies (d2, d3, d4, d5 and d6) and hormonal stimulation (0/y, 4/y, 8/y and 10/y) were applied. Whatever the stimulation regime, the average g.t-1.t-1 of the unstimulated control (56) of the active metabolism clones (PB 235, PB 310, IRCA 111 and IRCA 130) over 9 years was statistically the same order that of the stimulated patterns (54). The average g.t-1.t-1 of the control (60) was lower than that of the highest yielding stimulated patterns (67) of the clones (PB 330, PB 280, PB 260, IRCA 18 and IRCA 209). The average g.t-1.t-1of the unstimulated control (49) was significantly lower than that of the highest yielding stimulated treatment (57) of moderate metabolism clones (GT 1, BPM 24 and RRIC 100). The average g.t-1.t-1 of the unstimulated control (39) was significantly lower than that of the highest yielding stimulated treatment (70) of slow metabolism clones (PB 217 and PR 107). On a large scale and at tapping frequency (d2), the unstimulated latex harvesting system (d2 0/y) showed an average yield of (2341; 2266 and 1849 kg.ha-1.year-1 for the active, moderate and slow metabolisms, respectively) statistically comparable to those of the highest yielding tapping frequencies d3, d4, d5 and d6 all latex harvesting systems combined for the clones studied (2388; 2348 and 2256 kg.ha-1.year-1). These results show that it is possible to produce natural rubber without exogenous hormonal stimulation by judiciously playing on tapping intensity.