Genetic parameters and genotype-by-environment interactions for pulp-yield predicted using near infrared reflectance analysis and pulp productivity in Eucalyptus globulus

Near infrared reflectance analysis was used to predict kraft pulp yield of open-pollinated progenies from 70 families collected from six populations (subraces) across the natural distribution of E. globulus: West Otways, Strzelecki Ranges, Furneaux Islands, King Island, north east Tasmania and south east Tasmania. Three sites were sampled and all sample trees were also assessed for diameter and wood basic density. Genetic parameters for predicted pulp yield, pulpwood productivity (basic density multiplied by predicted pulp yield) and pulp production index (pulpwood productivity multiplied by tree diameter) were estimated together with the degree and practical importance of genotype by environment interactions for each trait Predicted pulp yield was under moderate genetic control (h2 ranging from 0.33 to 0.58), pulpwood productivity was under strong genetic control (h2 ranging from 0.33 to 0.58) and pulp production index generally under weak genetic control (h2 ranging from 0.80 to 0.84). Genetic correlations between diameter and predicted pulp yield were variable (ranging from -0.16 to -0.43) as were genetic correlations between basic density and predicted pulp yield (range 0.00 to 0.74). Genotype by environment interaction was not considered a major problem for predicted pulp yield and pulpwood productivity. Although significant interaction between the subraces and sites was found for predicted pulp yield there were no significant differences among subraces at one site and the range of subrace means was small. For predicted pulp yield the family by site interaction was not significant, genetic correlations between the sites were very high and the heritability estimated for the combined data set was similar to the average of the individual site estimates. Combining tree diameter, basic density and predicted pulp yield data into a single variable (pulp production index) is not recommended as the heritability was generally low and it was subject to significant genotype by environment interaction.