02673nas a2200181 4500008004100000022001400041245006700055210006700122260001200189300001400201490000700215520210700222100002002329700001602349700002802365700002002393856007802413 2008 eng d a0282-758100aIrrigation water and Phytophthora cactorum in a forest nursery0 aIrrigation water and Phytophthora cactorum in a forest nursery c10/2008 a404 - 4110 v233 a

Phytophthora cactorum (Lebert and Cohn) J. Schröt is known to cause stem lesions on Betula pendula Roth in Finnish nurseries. It has been suggested that irrigation water may be one source of infection. Therefore, P. cactorum was baited from pond water used for irrigation and direct isolations were made from necrotic stem lesions in a forest nursery during the years 2004–2006. Morphological characteristics, as well as sequencing of the β-tubulin gene and ITS1 region, confirmed the isolates as P. cactorum. The pathogen was present in the pond every year, but no diseased seedlings were found in 2005. The cultural and morphological characteristics showed high variation among the isolates, but it was not possible to identify the origins of the isolates according to them. In random amplified microsatellite (RAMS) analysis and DNA sequencing, the isolates from the pond and from the stem lesions were genetically similar, and the tested isolates were pathogenic. The results indicate that irrigation water is one source of stem lesion disease, and the microbe can overwinter in the pond. Two separate forms of the β-tubulin gene were detected in all the studied isolates, suggesting that the P. cactorum here carries two β-tubulin gene loci in its genome.

1 aRytkönen, Anna1 aLilja, Arja1 aPetäistö, Raija-Liisa1 aHantula, Jarkko uhttp://www.tandfonline.com/doi/abs/10.1080/02827580802419034#.UqfxDo25Ibg