Genetic variation in growth traits and yield of rubber trees (Hevea brasiliensis) growing in the Brazilian state of Sao Paulo

Analysis of variance and covariance was preformed on growth traits (stem girth, bark thickness, total height gain andrubber yield) of 22 open-pollinated progenies of the rubber tree Hevea brasiliensis from an Asian Hevea collection introduced to Agronomic Institute (Instituto Agronomico, Campinas, Sao Paulo, Brazil; IAC) in 1952. This progeny trial was replicated at three sites in Sao Paulo state and it was found that at three years from sowing there was statistically significant variation for girth, bark thickness, height and rubber yield. An individual test sites, values of individual plant heritability for girth ranged from (h) over cap (2)(i) = 0.36 to (h) over cap (2)(i) = 0.89 whereas values for heritability for progeny means ranged from (h) over cap (2)(i) = 0.77 to (h) over cap (2)(i) = 0.87. These moderate and high heritabilities suggest that a combination of progeny and within-progeny selection would be effective at increasing girth in this population at individual sites. Across sites, values of individual-plant heritability for girth ranged from i 2 = 0.36 to i 2 = 0.47, whereas values for heritability of progeny means girth ranged from (h) over cap (2)(x/) = 0.77 to (h) over cap (2)(x/) = 0.87. There were high positive genetic correlations between increased girth and bark thickness suggesting that breeding aimed at increasing girth would also increase bark thickness and possibly height.