ABSTRACT

Fourteen Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. Arg. genotypes were evaluated at the experimental station of the Rubber Research Institute of Institute of Nigeria, Ntang Inya in Uyo Akwa Ibom in 2011, 2012, 2012 and 2014 cropping seasons to generate information on the extent of genetic variation, heritability and genetic advance among. Also, to identify the most adaptable genotypes among the tested entries. As the knowledge and understanding of the magnitude of genetic variability is centered for selection and development of genotypes for specific purposes. The experimental design was randomized complete block design with four replications. Data collected on twenty one quantitative agronomic and yield characters were subjected to analysis of variance, correlation analysis, to estimate the extent of genetic variability, genetic variance, broad sense heritability and relationship of rubber yield and its component. The combined analysis of variance revealed significant differences (P<0.01) among the genotypes for all the studied characters indicating the inherent genetic differences among the genotypes evaluated. Genotype x year interaction was not significant (P>0.05) for seed thickness, seed length/thickness ratio, seed volume and bark thickness relative to all the other characters assessed. This implies that the performance ofthe genotypes was not consistent in the different years of evaluation. Year effect was significant (P<0.05) fbr all the characters except stem girth and seed density. High magnitude of phenotypic and genotypic coefficient of variations as well as high heritability along with high genetic advance recorded fbr stem girth, bark thickness, leaf area provides evidence that these characters were under the control of additive gene effects and effective selection could be possible fbr improvement of these characters. While the moderate heritability associated with low genetic advance obtained fbr rubber yield, seed circumference, seed weight, seed sphericity, seed surface area, seed geometric diameter revealed greater role of non additive gene action in its inheritance. Significant correlation of seed width, seed thickness, seed geometric diameter, seed surface area, seed sphericity, seed circumference, seed surface area/ seed weight with yield and that of bark thickness, seed length, seed width ,seed geometric diameter, seed surface area with stem girth suggested that these characters possessed greater values fbr selection. However, negative correlation between yield and stem girth, bark thickness, leaf width implies no direct relationship between them. The study identified high yielding genotypes; NIG 902, NIG 901, NIG 903, NIG 905, NIG 904, NIG 907, NIG 906, NIG 908 which can be recommended fbr farmers in Uyo agro ecology.