No abstract

No abstract

In order to test the agronomic performance of the newly developed clones, a Large-Scale Clone Trial (LSCT) comprising Hevea brasiliensis clones GT 1, IRCA 202, IRCA 331, IRCA 707, PB 280 and PB 310 was established in southwestern Côte d'Ivoire. They were planted in completely randomized blocks with six clone treatments and four replications of 112 trees per clone. The measured parameters included isodiametric growth of the trunk, rubber yield, trees stand, latex physiological parameters and sensitivity to tapping panel dryness (TPD). Collected data was analyzed using Statistica 7.0 statistical software. After ten years of downward tapping and four years of upward tapping, clone IRCA 331 showed significantly higher rubber productivity than all other clones. Its productivity gain, relative to the reference control GT 1, was 63% in downward tapping and 80% in upward tapping. Despite its high level of productivity, the annual rate of isodiametric growth of clone IRCA 331 tree trunks (2.56 cm/year) remained statistically equivalent to that of clone GT 1 (2.62 cm/year) at latex harvesting stage. In addition, the physiological profile of clone IRCA 331 was good and similar to that of the control. Clones IRCA 331, GT1 and PB 280 got the lowest sensitivity to TPD. However, only clones GT1 and IRCA 331 maintained a good stand of tappable trees throughout the experimental period. This experiment highlighted the agronomic performance of the clone IRCA331 and allowed to put it in class 1. Clone IRCA 331 can therefore be used as a clone of first choice to improve national productivity.

Rubber tree rapid-metabolism clones generally have interesting agronomic and physiological characteristics. However, they are mostly sensitive to tapping panel dryness and breakage due to wind. This could be probably due to overexploitation caused by high tapping frequencies and/or high hormonal stimulation systems. To try solving this problem, a study was carried out over nine years using clones PB 260, PB 280 and PB 330 planted at a density of 510 plants/ha in southwestern Côte d'Ivoire. The experimental design was a randomized complete blocks with different latex harvesting technologies. The estimated parameters were rubber yield, radial vegetative growth, physiological profile and the profitability of applied latex harvesting technologies. Results indicated that non-stimulated combined with high tapping frequency latex harvesting system (d2 0/y) showed a level of rubber yield comparable to that of tapping frequencies d3 and d4 in all studied clones irrespective of the level of hormonal stimulation applied. Furthermore, the absence of hormonal stimulation had no negative influence on the vegetative growth and the physiological profile of rubber trees. Every two days (d2) tapping system without stimulation generated a profit margin statistically identical to that of low tapping frequencies (d4, d5 and d6) irrespective of the level of hormonal stimulation.

No abstract