Clonal selection for resistance to Dothistroma needle blight in Pinus radiata.

Fifty-two clones in twenty-two full-sib families were represented in a field trial. All cuttings were taken from hedged ortets which were four years from seed, but had been cut back periodically to one metre high since age two. One-year-old seedlings, from a seed orchard, where most of the parents of the clones were represented, were used as controls. The trial was assessed for Dothistroma needle blight infection six years after planting. The mean infection level of all the cuttings was 21.1%, compared to 29.8% for the seedlings. This difference was attributed to the greater maturation age of the cuttings. It was calculated that if the best 10% of the clones were selected, infection could have been further reduced to 12%, a level where other disease control measures would be considered unnecessary. [ABSTRACT FROM AUTHOR]