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Maturation-Related Resistance of Pinus radiata to Western Gall Rust. D. Zagory, Graduate research assistant, Department of Plant Pathology, University of California, Berkeley 94720, Present address of senior author: Department of Environmental Horticulture, University of California, Davis 95616 ; W. J. Libby, professor, Departments of Genetics and of Forestry & Resource Management, University of California, Berkeley 94720. Phytopathology 75:1443-1447. Accepted for publication 28 June 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-1443.

Pinus radiata (common name, radiata pine) propagated from juvenile (hedged) and more mature (nonhedged) donor plants of the same set of clones were compared to determine the effects of maturation on resistance to western gall rust, which is caused by the fungus, Endocronartium harknessii. The more mature plants had significantly fewer stem and branch galls than did the more juvenile ones during 2 yr following exposure to heavy natural inoculum. Clonal heritabilities were generally high and interactions between clones and maturation states were near zero. The use of selected clonal planting material and the manipulation of the maturation state of those clones may be useful in reducing the impact of western gall rust on P. radiata.

Additional keywords: clonal forestry, disease resistance, ontogenetic ageing, Peridermium.