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Histopathology of Fusiform Rust-Inoculated Progeny from (Shortleaf Slash) Shortleaf Pine Crosses. F. F. Jewell, Sr., Professor, School of Forestry, Louisiana Tech University, Ruston 71272; Phytopathology 78:396-402. Accepted for publication 3 September 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-396.

Progeny from (shortleaf slash) shortleaf pine crosses, inoculated at age 6 wk with fusiform rust, were sampled and examined histologically 1 yr following treatment. Similar uninoculated progeny were used as controls. No consistent reaction of the host progeny to the rust pathogen was observed. In general, three distinct host-parasite relationships were identified: typically susceptible, with host characteristics typical of the rust gall anatomy of a susceptible pine-fusiform rust interrelationship; pseudoresistant, with the host expressing normal tissue deposition and anatomical features (resistance zones) considered limiting to the advance of the pathogen, but from which it egressed to establish typical gall-forming tissue in the host; and resistant, with evidence of pathogen establishment in the pith area of the host followed by the formation of normal-appearing tissues through the xylem to the cortex area and no indication of pathogen viability evidenced in the affected host tissue. This third type of host reaction suggests that reliable resistance to fusiform rust can be obtained by backcrossing certain southern pines.