Effect of Photoperiod and Container Size on Sugar Pine Seedling Growth and Infection by White Pine Blister Rust

摘要

Continuous illumination of sugar pine seedlings promoted early secondary needle formation and increased foliar symptoms of white pine blister rust after artificial inoculation at the end of one growing season. The greater intensity of symptoms expressed by seedlings grown under continuous illumination, compared with those grown under natural and extended 16-hour photoperiods, appeared to be an effect of predisposition. The hypersensitive response to infection on seedlings of known resistant genotype was expressed under both long and natural photoperiods. Container size did not significantly affect infection intensity. Seedlings weight, height, and diameter varied directly with container size. Seedlins grown under extended photoperiods had greater dry weights than those under a natural photoperiod, but only seedlings grown under the 16-hour photoperiod grew taller.