Ethephon-mediated regulation of latex production, biosafety, and quality attributes in Hevea brasiliensis clone CATAS 73397 under a four-day tapping system

In response to the challenges of relatively low natural rubber (NR) quality in China and the lack of suitable tapping techniques for major rubber tree ( Hevea brasiliensis ) clones to enhance yield while maintaining quality, this study systematically evaluated the effects of three concentration gradients of ethephon (ET) stimulation (0.0 %, 1.0 %, and 1.5 %) on latex yield, physiological characteristics, tapping panel dryness (TPD) incidence, and raw NR quality of CATAS 73397 mid-aged rubber trees under a conventional low-frequency tapping system (S/2 d4). The results demonstrated that 1.0 % ET stimulation significantly increased dry rubber yield (DRY) by 88.26 % without compromising raw NR quality and elevating TPD risk. However, higher concentration stimulation elevated TPD risk and reduced rubber quality. This indicates that to balance yield, quality, and safety, appropriate ET stimulation is permitted to meet the actual needs of production. Under the S/2 d4 tapping system, a 1.0 % ET concentration proved more suitable for mid-aged CATAS 73397 rubber trees than 1.5 %, as it effectively boosted yield while ensuring safety and quality retention. Correlation analysis revealed that latex parameters such as nitrogen (N) content, total solids content (TSC), inorganic phosphorus (Pi) content, and sucrose (Suc) content exhibited significant (or highly significant) negative correlations with raw NR indicators including initial plasticity values (P 0 ) and Mooney viscosity (V R ), but highly significant positive correlations with plasticity retention index (PRI). These findings suggest that latex physiological characteristics are closely linked to raw NR quality, indicating their potential as predictive markers for quality assessment. This study establishes an optimized tapping protocol for CATAS 73397 to achieve both quality preservation and yield increase. Additionally, it provides a theoretical foundation for the scientific selection of stimulant concentrations and real-time monitoring of raw NR quality in production practices. • Appropriate ET stimulation is permitted to balance yield, quality, and safety, thereby meeting actual production needs. • Application of 1.0 % ET increase dry rubber yield by 88.26 % without compromising quality. • Higher concentrations of ET elevate the risk of TPD and reduce raw rubber quality. • Latex physiological parameters show a strong correlation with raw rubber quality indicators.