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Comparative Anatomy and Host Response of Two Peach Cultivars Inoculated with Leucostoma cincta and L. persoonii. A. R. Biggs, Research scientist, Agriculture Canada Research Station, Vineland Station, Ontario L0R 2E0; Phytopathology 76:905-912. Accepted for publication 11 March 1986. Copyright 1986 Department of Agriculture, Government of Canada. DOI: 10.1094/Phyto-76-905.

Stems of 2-yr-old peach cultivars, Candor (susceptible) and Sunhaven (relatively resistant), were inoculated in the greenhouse with mycelium of either Leucostoma cincta or L. persoonii, and sampled for histological study and pathogen reisolation at 14, 28, and 56 days postinoculation. Additional plants were wounded and sampled at 6, 8, 10, 14, 28, and 56 days postwounding. The cultivar Candor was initially colonized by both fungi more extensively than the cultivar Sunhaven. With time, cultivar differences were less important than differences in fungal virulence. Discontinuities or points of weakness in new periderms were detected in both wounded and inoculated samples. Sites of periderm circumvention and ingress by fungi into previously healthy tissues included the juncture of wound periderm with healthy periderm and with primary phloem fibers, and the nonsuberized centripetal surface of juvenile callus tissue. The expansion and coalescing of gum ducts caused the rupture of suberized xylem parenchyma boundaries, thus providing entry sites for the pathogens. Suberization of extant xylem ray parenchyma internal to wounds was observed in all wounded samples but in only one of nine inoculated samples. The results suggested that peach cultivars varied in their ability to establish anatomical barriers in bark and xylem and that Leucostoma spp. inhibited suberin deposition in xylem barrier zones.