Seasonal variation in rubber yield, physio-biochemical parameters and sucrose metabolism-related genes in two rubber tree cultivars

Sucrose metabolism is essential for the biosynthesis of natural rubber in the para rubber tree (Hevea brasiliensis), but its seasonal regulation remains poorly understood. Here, over a two-year period, we conducted a comprehensive investigation of seasonal fluctuations in rubber yield, physio-biochemical parameters, and sucrose metabolism-related genes in high-yielding Reyan7–33–97 and low-yielding PR107 rubber tree cultivars. Our results showed that rainfall exerted a stronger influence on seasonal rubber yield fluctuations than temperature, and that Reyan7–33–97 was more sensitive to rainfall variation. Comparative analyses uncovered distinct seasonal patterns in sucrose metabolism-related physiological, biochemical, and molecular parameters in both latex and trunk bark tissues, which likely underlie the yield divergence between the two cultivars. Of the 15 physio-biochemical parameters examined, latex dry rubber content (DRC), latex inorganic phosphate (Pi), and latex sucrose synthase activity in the cleavage direction (SSC) were significantly positively correlated with yield, whereas bark reducing sugar (RS) showed a significant negative correlation. These four parameters may thus serve as reliable indicators for rubber yield prediction under fluctuating seasonal conditions. Moreover, the expression levels of several sucrose metabolism-related genes also exhibited associations with rubber yield. Among them, HbSus3 emerged as a key candidate for evaluating yield variations in rubber tree cultivars. These findings deepen our understanding of seasonally regulated rubber biosynthesis and provide valuable indicators for yield assessment under seasonal variation, as well as candidate genes for breeding high-yield rubber trees.