It is well known that the productivity and the susceptibility to the tapping panel dryness (TPD) of Hevea brasiliensis are determined by the intrinsic feature of each clone but also by the tapping system. Thus, in order to establish the tapping system that minimizes the TDP occurrence an experiment was carried out in Côte d'Ivoire with four high yielding clones including, PB 235, PB 255, IRCA 18 and IRCA 111. Five tapping systems (d2 6d/7 0/y, d3 6d/7 4/y, d4 6d/7 6/y, d5 6d/7 8/y, d6 6d/7 10/y) were applied to these clones, corresponding to a range of 100 % to 30 % of tapping intensities. The results show that the occurrence of TPD is closely related to the tapping intensity and the tapping system which consists in tapping twice per week with one day rest (S/2 d3 6d/7 4/y), was found to be the best tapping system. A quadratic relation was found between the rate of the TPD and the tapping intensity. Thus the clones IRCA 18 and IRCA 111, like PB 235 and PB 255, belong to the active metabolism clones. These clones also showed their adherence to the group of high rubber producer clones. This experiment also gave further evidence that the production of a tree for the tapping strongly depends on the intensity of tapping. It has also indicated that the intensity of tapping governed the tapping panel dryness rate among the clones having active metabolism, such as IRCA 18, IRCA 111, PB 235 and PB 255.

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.