%0 Journal Article
%T Effects of Pythium Species and Time in Cold Storage on the Survival of Bareroot and Container-Grown Southern Pine Seedlings
%A D. Paul Jackson
%A Scott A. Enebak
%A David B. South
%J ISRN Ecology
%D 2012
%R 10.5402/2012/874970
%X Cold storing bareroot southern pine (Pinus spp.) seedlings for greater than one week after lifting in the fall can lead to poor outplanting survival when compared to seedlings that are lifted and stored in winter. In contrast, container-grown seedlings typically do not experience adverse effects from storing for periods greater than one week. The practice of lifting bareroot seedlings can cause wounds to root systems, which could allow soil-borne pathogens such as Pythium species to be used as infection sites. Once seedlings are placed in storage, the cool, moist environment may be conducive for zoospore activity, leading to root disease and outplanting failure. Bareroot and container-grown longleaf pine (Pinus palustris), loblolly pine (Pinus taeda), and slash pine (Pinus elliottii) and container-grown shortleaf pine (Pinus echinata) were inoculated with either Pythium dimorphum or Pythium irregulare, cold-stored for 3, 4, 6, or 12 weeks, and outplanted. Both Pythium species reduced survival of bareroot longleaf pine but not bareroot slash pine. Length of storage decreased survival for both seedling stock types. Pythium species did not affect the survival of container-grown seedlings. These results suggest that P. dimorphum and P. irregulare are more virulent to bareroot longleaf pine than the other pine species tested. 1. Introduction In the southern USA, forest tree nursery managers commonly hold pine (Pinus spp.) seedlings in cold storage (<5¡ãC) after lifting when transplanting operations are stopped due to adverse weather. Bareroot seedlings lifted and held in long-term cold storage (>1£¿wk) in the fall (before the winter solstice) can result in poor seedling survival compared to when seedlings are lifted and stored during winter months. For example, Kahler and Gilmore [1] reported loblolly pine (Pinus taeda) seedling survival to be less than 60% when lifted and cold-stored in the fall and greater than 90% when lifted and cold-stored after the winter solstice. In another study, loblolly pine seedlings lifted in the fall and stored for two weeks had less than 3% survival, while survival without storage ranged between 66 and 92% [2]. Two theories exist to explain why bareroot pine seedling survival is poor following lifting and cold storage during the fall season. The first theory involves the lifting of seedlings that have nondormant buds or that have not been exposed to a certain number of chilling hours. Chilling hours is defined as the exposure of seedlings to above-freezing temperatures (<8¡ãC) for a specific period of time, and after this time
%U http://www.hindawi.com/journals/isrn.ecology/2012/874970/