VIEW ARTICLE

Sucrose and Cell Walls as Factors Affecting Phoma Storage Rot of Sugar Beet. W. M. Bugbee, Research Plant Pathologist, Plant Science Research Division, ARS, USDA, Fargo, North Dakota 58102; Phytopathology 63:480-484. Accepted for publication 26 September 1972. DOI: 10.1094/Phyto-63-480.

Sucrose concentration and resistance of sugar beet storage roots to Phoma betae increased with age. Growth of P. betae on isolated cell wall material in culture also increased with the age of roots, but the production of endopolygalacturonate trans-eliminase (endoPGTE) decreased up to 142 days, then increased. Cell walls from a fodder cultivar induced more endoPGTE than cell walls from two sugar cultivars. Commercial cultivars that were higher in sugar remained resistant, whereas the low sugar, fodder cultivar became more susceptible. There was a significant negative correlation between the sucrose percentage and disease rating of defoliated and nondefoliated plants. Phoma betae produced more endoPGTE when cultured on cell wall material from defoliated than from nondefoliated plants. Enzyme production was not affected by sucrose percentage of root tissue or cultivar. Individual roots that expressed a resistant reaction to P. betae usually had a high sucrose percentage. But the association of resistant roots with resistance to maceration by culture filtrates and the production of endoPGTE on isolated cell wall material suggest that the properties of cell walls as well as sucrose content affect pathogenesis and the activity of endoPGTE.