116 DOI: 10.1002/jpln.200520562 J. Plant Nutr. Soil Sci. 2006, 169, 116–117 Short Communication Root border cells from Picea abies stimulate the germination of Fusarium sp. and Cylindrocarpon sp. conidia Toril D. Eldhuset 1 *, Isabella Børja 1 , and Berit Swensen 1,2 1 Norwegian Forest Research Institute, Høgskoleveien 8, N-1432 Ås, Norway 2 Present address: Herumveien 33, N-1430 Ås, Norway Accepted November 20, 2005 Key words: border cells / spore germination / Norway spruce / Fusarium / Cylindrocarpon PNSS P05/62P 1 Introduction Border cells are living cells sloughed off from the root cap. They have their own metabolism and are supposed to play roles in defense mechanisms against, e.g., nematodes and fungal pathogens, and in protection of roots to aluminum (Al) toxicity (Hawes et al., 2000; Zhu et al., 2003). Border cells from Norway spruce (Picea abies) have not been studied ear- lier. In this work, we studied the effect of Norway spruce bor- der cells on germination of Fusarium sp. and Cylindrocarpon sp. conidia, two soilborne fungi that are considered to be root pathogens on Norway spruce seedlings. 2 Material and methods 2.1 Plant material Aseptic Norway spruce seeds were germinated on moist filter paper in the presence or absence of 1.5 mM AlCl 3 until the roots were about 15 mm long. A border-cell suspension was prepared by vortexing five root tips in 1 mL of sterile water for 30 s. 2.2 Fungi Cultures of Fusarium sp. (culture No. 87–1225/3) and Cylin- drocarpon sp. (culture No. 87–672/2), both originally isolated from the roots of Norway spruce seedlings with root-dieback symptoms, were used. Fungi were cultivated on malt-extract agar medium until the dish surface became covered with mycelium. On the mycelial mat in each Petri dish (two dishes per each fungal culture), 2 mL of sterile MilliQ H 2 O were pipetted. Dishes were stirred in order to gather the conidia. The conidial suspension (4 mL) was pipetted again into a Falcon tube and filled with MilliQ H 2 O until 7 mL. 2.3 Germination of conidia The treatments are shown in Tab. 1. Eppendorf tubes were placed in a rack in a transparent moisture chamber. Into each tube, we pipetted 250 lL conidium suspension. We added 250 lL MilliQ H 2 O (treatment 1) or malt extract (treatment 2). In treatments 3–4, we added 250 lL border-cell suspension. In treatments 5–9, we added five roots or seedlings in 250 lL MilliQ H 2 O. There were four repetitions of each treatment. Extent of conidial germination was evaluated visually using light microscope at 400x magnification 2, 5, 12, 22, 28, and 96 h after inoculation. 3 Results and discussion In both species, conidia in water without border cells began to germinate within 5 h (treatment 1 in Fig. 1). At 96 h, about 35% of the Fusarium and 50% of the Cylindrocarpon conidia had germinated. The presence of border cells, either sloughed off (treatment 4) or still attached to the cut-off root tips (treatment 9), clearly stimulated the germination of fungal conidia in suspension and lead to 90%–100% germination within 12 h. Addition of malt extract (treatment 2) caused a similar stimulation as border cells. By contrast, border cells from seedlings grown in the presence of Al (treatment 3) had no stimulating effect in Fusarium and led to decreased germi- 0 20 40 60 80 100 120 0 2 5 12 22 28 96 Hours after inoculation Germination of conidia (%) 1 2 3 4 6 9 0 20 40 60 80 100 120 0 2 5 12 22 28 96 Hours after inoculation Germination of conidia (%) 1 2 3 4 6 9 A B Fusarium Cylindrocarpon Figure 1: Germination of Fusarium sp. (A) and Cylindrocarpon sp. (B) conidia. For an explanation of treatments see Tab. 1. Results from treatments 5, 7, and 8 are not shown. * Correspondence: Dr. T. D. Eldhuset; e-mail: toril.eldhuset@skogforsk.no