Comparative Performance of Natural Rubber (<i>Hevea Brasiliensis</i>) Polyclonal and Multiclonal Bud Grafted Population in Suboptimal Environment of Odisha, India

Abstract

The natural rubber ( Hevea brasiliensis ) yield and growth performance of polyclonal rubber seedlings was evaluated and compared with an adjacent multiclonal population comprising of three clones RRII 105, RRIM 600 and GT1 in the dry sub humid climate of Odisha state, which experiences high temperature and low rainfall as the major environmental constraints for the growth and yield of the crop. The study revealed that seedling population is highly heterogeneous with respect to yield, growth and other secondary characters. Tappable girth was attained earlier in polyclonal population as compared to multiclonal population. The Mean annual girth increment was also higher in polyclonal population (5.95 cm) as compared to multiclonal population (3.90 cm). Mean annual rubber yield of 34.02 gt -1 t -1 was recorded in polyclonal population over a five years period as compared to 25.10 gt -1 t -1 for multiclonal population. Some polyclonal seedlings genotypes are outstanding performers, which recorded even two to threefold higher rubber yield than the mean of the multiclonal population. Ten elite mother trees with high yield over the five year period were selected for further evaluation. The highest mean dry rubber yield was recorded in OR2 (75.40 gt -1 t -1 ) followed by OR3 (69.04 gt -1 t -1 ) and OR7 (64.18 gt -1 t -1 ) among the ten elite seedling mother trees. Highest yield contribution was recorded during the cold months for polyclonal as well as multiclonal population. The highest annual girth increment before and after tapping was recorded in OR1 (10.16 cm) and OR7 (4.68 cm), respectively. In addition to the yield and growth, the population was assessed for bole volume, bark thickness and incidence of tapping panel dryness and wind damage. Polyclonal population also recorded comparatively less wind damage and tapping panel dryness. Bole volume was significantly higher (0.27 m³/tree) for polyclonal as compared to multiclonal population (0.08 m³/tree). The present study, in a sub-optimal environment of Odisha of eastern India, reveals the large variation among the population and ample scope for selection of promising genotypes from poly cross progeny suited to the sub optimal environment.