Résumé
This study (Part 1) is the first of a two-part series investigating how reduced tapping frequency, combined with hormonal stimulation, impacts latex yield, as well as biochemical composition and structure (particle size) of latex in two Hevea brasiliensis clones (RRIM600 and RRIT251) over 4 years of tapping. The trial was set in Udon Thani, Thailand, a non-traditional area for rubber cultivation. Results show that the S/2 d3 ET 2.5 % Pa 0.7 tapping system significantly increased latex yield per tapping without compromising cumulative production per tree compared to the conventional S/2 d2 system. As compared to RRIM600, clone RRIT251 exhibited superior yield potential, supported by higher biochemical indicators such as sucrose, inorganic phosphorus, and reduced thiols, reflecting robust metabolic activity and antioxidant capacity in latex cells. Biochemical characterization revealed clonal differences in latex composition: RRIM600 displayed larger rubber particles and higher neutral lipid content, while RRIT251 showed higher levels of phospholipids and proteins. Despite these differences, the tapping system had minimal impact on latex biochemical properties, highlighting the role of hormonal stimulation in maintaining rubber biosynthesis. These findings emphasize the importance of clone-specific strategies in optimizing yield and resource efficiency. Furthermore, this study provides a basis for the subsequent analysis of how tapping systems and clonal variations influence the properties of latex-derived materials, including latex films and technically specified rubber samples (TSR5 and TSR10), as detailed in Part 2 of this study (Liengprayoon et al.). This research contributes to developing sustainable latex tapping practices tailored to specific clones and tapping systems.