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Resistance

Testing of Pinus pinea and P. pinaster Progenies for Resistance to Cronartium flaccidum. P. Raddi, Geneticist, Centro di studio per la Patologia delle specie legnose montane, Consiglio Nazionale delle Richerche, Presso l’Instituto di Patologia Forestale e Agraria, delle Università, Piazzale delle Cascine, 28, 50144 Firenze (Florence), Italy; L. Mittempergher(2), and F. Moriondo(3). (2)Geneticist, Centro di studio per la Patologia delle specie legnose montane, Consiglio Nazionale delle Richerche, Presso l’Instituto di Patologia Forestale e Agraria, delle Università, Piazzale delle Cascine, 28, 50144 Firenze (Florence), Italy; (3)Associate professor of Forest Pathology, University of Florence, 50144 Florence, Italy. Phytopathology 69:679-681. Accepted for publication 18 January 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-679.

Seedlings of 33 half-sib maritime pine (Pinus pinaster) families and 40 Italian stone pine (P. pinea) families were artificially inoculated with basidiospores of Cronartium flaccidum produced on rusted white swallowwort leaves. Italian stone pine was highly susceptible; 99.9% of tested seedlings had needle spot symptoms of the blister rust disease. No rust resistance was found in this species; 93% of the seedlings died. Maritime pine was less susceptible than the first species. Significant differences were observed among families for the amount of infection of the needles and for survival of seedlings with needle spots. In as many as 22% of the spotted seedlings the pathogen failed to become established in the stem. The heritability values for the needle infection character (0.124 ± 0.039) and the survival of “spotted-only” seedlings (0.156 ± 0.046) suggested that a breeding program for resistance of maritime pine to blister rust is feasible.