3 SELECTING PINUS RADIATA FOR RESISTANCE TO DOTHISTROMA NEEDLE BLIGHT

Dothistroma needle blight caused by Dothistroma pini Hulbary was assessed on Pinus radiata D. Don in New Zealand in nine progeny trials ranging in age from 2 to 10 years. Resistant families could be identified from all assessments and rankings were consistent over sites and years. Heritabilities were moderately high, specific combining ability (SCA) was very small compared to general combining ability (GCA), and there was no indication of substantial genotype x location interaction. The greatest net gain in volume from resistant progeny will result from placing as much selection emphasis on Dothistroma resistance as on improved growth rate and stem form. Genetic gain expected from seed orchard progeny from performance-tested first-generation parents is calculated from progeny test data to be about 11-12%. The actual reduction in disease with disease-resistant stock may be greater because of the epidemiological effect which occurs when all trees in a stand are resistant