Yield and related attributes of certain new generation clones of hevea brasiliensis under large scale evaluation

Twenty clones comprising 15 of the rrii 400 series,one introduced prang besar clone,one tetraploid and three clones with normal morphotype (derived from the progeny of the compact canopy type variant) were evaluated in large scale evaluation trials over a period of 16 years. the components of variance for yield in two virgin panels,growth and structural attributes,heritabilities of traits and their correlations were studied. rubber yield which stabilised by the fourth year of tapping and yield per unit girth emerged as highly heritable traits with girth,girth increment at immaturity and the number of latex vessel rows being important clonal characteristics,showing positive correlations with yield in the two virgin panels. clones rrii 430,rrii 417,rrii 422 and rrii 414 maintained superiority in rubber yield over the high yielding check,rrii 105 over eight years of tapping,justifying their release for wide scale planting in the traditional rubber growing regions of india. clones rrii 417,rrii 422 and rrii 430 were distinctly superior to rrii 105 in terms of rubber yield per unit girth. these three clones also exhibited wind fastness. among the promising yielders,clones rrii 414,rrii 422 and rrii52 maintained high summer yields. clone rrii 430 recorded a comparatively low incidence of pink disease. pb 330 proved to be a moderately high yielding clone with a rising yield trend and very high timber yield potential. clones rrii 429 and rrii 422 were superior for the number of laticifers in the bark.