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Histopathology of One- and Two-Year-Old Resisted Infections by Cronartium fusiforme in Slash Pine. F. F. Jewell, Professor, Forest Protection, School of Forestry, Louisiana Tech University, Ruston 71270; Daphne C. Speirs, Research Assistant, School of Forestry, Louisiana Tech University, Ruston 71270. Phytopathology 66:741-748. Accepted for publication 4 December 1975. DOI: 10.1094/Phyto-66-741.

Anatomical resistance to Cronartium fusiforme 1 and 2 years after artificial inoculation of slash pine seedlings 5-7 weeks of age was expressed by localized zones of dark-staining living and nonliving tanninized host cells. Resistance-zones were delimited by atypical vertical (reaction) parenchyma. Extent of zones depended on age of the host sample, with greatest expression occurring in 1-year-old infected seedlings. A regression of zones in 2-year-old samples, in some cases to only remnants remaining deep in the xylem next to the pith, indicated the probability of complete recovery with increased host age and growth. Hyphae of C. fusiforme were limited to the resistance-zones and were considered viable in bordering reaction parenchyma. Although hyphae were common in the tanninized cells of the resistance-zone, hyphae appeared to be nonfunctional.

Additional keywords: pathological anatomy, Pinus elliottii var. elliottii, rust resistance.