Dynamics of long-term adaptive responses in growth and rubber yield among Hevea brasiliensis genotypes introduced to a dry sub-humid climate of Eastern India

The twentieth century has witnessed a transformation of Para rubber (Hevea brasiliensis) from a wild tree species to a major plantation crop of South and Southeast Asia. In India, rubber cultivation was started in Southern India because of agro-climatic suitability, but pressure on land resources has necessitated further expansion to neighbouring areas. Earlier attempts to afforest isolated pockets of Central and Eastern India have met with limited success due to various factors. This paper reports a long-term evaluation (sixteen years) of niche adaptation of twelve rubber clones introduced to Eastern India. The growth and survival pattern indicated good adaptability for certain clones such as RRII 430 that recorded the highest girth and tappability. Early yield pattern identified RRII 429, RRII 430, and RRII 422 as higher yielders having 20-30% yield advantage over the control clone RRIM 600. The clones PB 217, RRIM 600, RRIC 100, and RRII 203 showed better stability and moderate yield rankings. There was individual clonal dominance for yield components such as dry rubber content (RRIC 100, RRII 417), bark thickness (RRII 203), and number of latex vessel rows (RRII 430, RRII 417). This is the first report on the performance of the latest Indian rubber clones of the RRII 400 series from the region. The clonal adaptability in this region that can be translated into commercial benefits included rising trend in latex yield and desirable secondary traits. Due to the uncertainty of stress occurrence in the non-traditional regions, planting of genetically variable clones (multiclones) in commercial plantings is important to impart adaptive plasticity. The results assume prominence in the context of expansive rubber cultivation and improving productivity in non-traditional areas and for international multilateral clone exchange aimed at improving global rubber productivity.