Selection of pipeline clones of para rubber tree ( Hevea brasiliensis ) for two divergent environments with cold and drought stresses

Forty-five superior genotypes (or “ pipeline clones ”) of Para rubber tree ( Hevea brasiliensis ) were screened for their adaptability to sub-optimal environments of India viz. Agartala (Tripura State) and Dapchari (Maharashtra State), which experience cold and drought stresses, respectively. The clones were evaluated for their growth and yield in clonal nurseries at the above two sites along with a comparative trial in a traditional environment (Chethackal, Kerala). Of the two sub-optimal environments, clones displayed better growth and yield at Agartala suggesting better adaptability of these clones to cold stress. Analysis of genetic parameters also supported this trend. The pipeline and control clones showed the lowest girth and yield in Dapchari environment which is prone to severe drought conditions. However, the clones had better girth and yield in Agartala, which is affected by cold stress, than in the conditions of Chethackal. For girth and yield, the broad-sense heritability estimated at the clonal level was lower in Dapchari than in the other two environments. Under cold-prone environment, five clones P 102 (35.8 cm), P 107 (35.6 cm), P 021 (34.7 cm), P 101 (32.1 cm) and P 059 (31.5 cm) achieved better or similar girth when compared to control clones, RRII 429 (33.9 cm), RRII 430 (32.8 cm) and abiotic stress-tolerant clone RRIM 600 (31.7 cm). Under drought stress environment, two clones P 102 (25.4 cm) and P 026 (21.8 cm) gave better girth than drought-tolerant clone RRII 208 (20.6 cm). Under traditional environment at Chethackal, control clone PB 260 (28.6 cm) along with RRII 414 (27.5 cm) achieved better girth. In terms of yield, P 107 (124.8 g/t/10t) gave maximum yield in the cold environment. In the same environment, P 057 (113.2 g/t/10t) gave a yield comparable with that of high-yielding control clone RRII 430 (114.5 g/t/10t). In the drought-prone region, control clone RRII 430 (57.1 g/t/10t) gave maximum yield. Three clones P 026 (52 g/t/10t), P 061 (47.6 g/t/10t) and P 015 (44.3 g/t/10t) also gave better yield as compared to control clone RRIM 600 (42.7 g/t/10t). Two clones P 027 (43.0 g/t/10t) and P 060 (42.7 g/t/10t) gave a yield which was comparable with RRIM 600 (42.7 g/t/10t). Eleven clones gave better yield than the region-specific control clone RRII 208 (38.2 g/t/10t). Under traditional environment, the control clone RRII 430 (130.8 g/t/10t) gave highest yield. Among clones, P 074 (112.1 g/t/10t) gave high yield as compared to control clone RRII 414 (111.9 g/t/10t). Two clones P 044 (106.0 g/t/10t) and P 026 (102.5 g/t/10t) gave better yield than control clone PB 260 (99.5 g/t/10t). Three clones P 015 (99.5 g/t/10t), P 110 (99.0 g/t/10t) and P 078 (98.4 g/t/10t) gave good yield comparable with control clone PB 260. Eleven clones gave better yield performance than control RRII 105 (66.6 g/t/10t). Twelve clones with superior growth and yield were identified as candidate clones for cold-prone environment. Similarly, twelve clones were identified as candidate clones for drought-prone environment. Eleven clones were identified as potential candidate clones for the traditional environment. Based on overall performance in terms of growth and yield under drought and cold environments, four clones P 020, P 026, P 102 and P 107 and the hybrid control clone RRII 430 were identified as having potential to evolve into climate-resilient clones. Two clones P 020 and P 026 along with the control clone RRII 430 appeared to possess multifarious adaptability for traditional as well as sub-optimal environments.