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A Rapid Axenic Assay for Hypersensitive Resistance of Pinus lambertiana to Cronartium ribicola. Alex M. Diner, Department of Botany, North Carolina State University Raleigh 27650; Ralph L. Mott, Department of Botany, North Carolina State University, Raleigh 27650. Phytopathology 72:864-865. Accepted for publication 19 November 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-864.

Axenic cultures of Cronartium ribicola were used as inocula for young embryos of Pinus lambertiana from seed lots expressing either blister rust susceptibility or hypersensitive resistance to the disease in the seedling or mature tree. Light-microscopic examination of both groups 14 days after inoculation showed characteristic expression of progressive disease in the embryos of susceptible genotypes and tissue necrosis with limitation of the disease in embryos of the hypersensitive genotype. This rapid in vitro display of resistance characteristics is independent of both the “natural” mode of host penetration via stomates and the ontogenic state of the inoculum. The assay should prove useful in breeding for host resistance and in studies of host-parasite biology.