Breeding against dothistroma needle blight of radiata pine in Australia

Pine needle blight, caused by Dothistroma septosporum (Dorog.) M. Morelet, is one of the most serious foliar diseases of Pinus spp. in Australia and New Zealand. In 16 Pinus radiata (D.Don.) progeny trials in northeastern Victoria, Australia, Dothistroma-caused defoliation varied widely among trials and assessment years, ranging from 5% to 65%. The estimated narrow sense heritability ranged from nonsignificant to as high as 0.69 with a median of 0.36. Spatial autocorrelation of residuals accounted for a significant proportion of residual variance, and that increased heritability estimates. Genetic correlation between defoliation scores at an early age and growth at a later age was negative with a median value of –0.39. Phenotypic correlation between defoliation and survival was low and negative with a median value of –0.11. Economic analyses indicated that at sites with a high risk of infection, the effect of reducing defoliation on profitability was comparable with that of increasing growth at sites free from infection. The genetic parameters and economic impacts of Dothistroma were used to derive selection indices and include resistance to defoliation into the current breeding objective for radiata pine.