Use of yield-yield correlation for early selection of newly developed Hevea genotypes

Abstract

In Hevea breeding and selection procedure, evaluation of genetic potential of newly developed genotypes under small scale clonal trials takes a minimum of 10-12 years. With the objective of shortening this period, statistical analysis of yield of thirteen years old 102 different Hevea genotypes belonging to three hand pollinated progenies established at Kalutara and Ratnapura districts was conducted. The effects of genotype, year and genotype versus year interaction were highly significant for all three progenies for girth and yield. Phenotypic correlation coefficients revealed significant yield – yield correlation between yields of 5th/7th year tapping and yields of younger tapping years. Spearman’s rank correlation coefficients were significant for all combinations tested except first year yield of progeny 90HP at Kuruwita. Starting early selection of best thirty percent of genotypes at the end of first year of tapping based on Spearman ranks of genotypes, it would be able to select successfully around 33.4% to 54.6% of genotypes, nearly 6 years earlier than the general selection procedure. Subsequent selections can be added later for further testing and nearly 90% of selections are possible before the final selection point. In two progenies tested it was possible to select nearly 81 % of the genotypes by the second year of tapping where as in the other progeny the portion selected was 46.4%. In subsequent selection steps, success of selection was increased which decreased the selection wastage. The evaluation process can be accelerated by 6 – 7 years by taking these selections to an “interim clone recommendation” for further evaluation under large scale estates in collaboration with the Rubber Research Institute. It maximizes the gain per unit time of Hevea breeding and shortens the evaluation process.