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O23 Nechwatal

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Information about O23 Nechwatal

Published on November 24, 2008

Author: bongsoopark

Source: slideshare.net

Description

2008 Phytophthora Workshop in Italy
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Flooding events and rising water temperatures increase the significance of the reed pathogen Pythium phragmitis Jan Nechwatal, Anna Wielgoss, Kurt Mendgen Universität Konstanz, Phytopathology, Konstanz, Germany

Reed (Phragmites australis) Perennial grass Worldwide distribution Littoral sites, up to 2m deep water Economic value Ecological value www.BioLib.de

Reed (Phragmites australis) Lake Constance (Bodensee) Surface area 536 km² Max. depth 254 m Shore length 273 km Max. length 63 km Max. breadth 14 km

Reed Decline Lake Constance reed belt area loss 1998-2000: approx. 24 % (Germany) from: Dienst & Schmieder, www.bodensee-ufer.de Hypotheses: - mechanical damage (recreation, boats, floating debris) - water eutrophication - animal feeding (insects, birds) - reed damage shown to be related to flood duration, time and depth - oxygen deficiency, anaerobic metabolism „flood-induced reed dieback“ (Ostendorp, Dienst & Schmieder, 2003)

The Reed Pathogen: Pythium phragmitis Nechwatal et al., 2005 sporangia oospores

The Reed Pathogen: Pythium phragmitis Grass-associated clusters B1d and B1e (Lévesque & de Cock, 2004) Van der Plaats-Niterink, 1981 Nechwatal et al., 2005 P. arrhenomanes Drechsler (1928)

P. phragmitis: The Damage it Causes oospore © J.N. … to seedlings … to mature leaves … no damage to roots and rhizomes infection mainly via leaves

P. phragmitis: The Role of Flooding Events 20 cm + P. phragmitis – P. phragmitis 2000 ml + P. phragmitis – P. phragmitis 25 plants (6-8 wks. old) per treatment

P. phragmitis: The Role of Flooding Events 1. plants fully submerged, all leaves below water line, 3 weeks 100 control 80 % live plants 60 40 20 Pythium 0 11 13 15 18 20 22 days post inoculation Regeneration shooting, 2 wks. after harvesting (= 36 dpi) Control: 5-8 cm per plant Pythium: 0

P. phragmitis: The Role of Flooding Events 2. plants partly submerged, 50 or 75% of plant height, 4 weeks 50 Mean shoot length (live shoots) 40 30 [cm] 20 10 a b a b 0 % % 0% 5% 50 75 l5 l7 50 % dead shoots um um tro tro i i on on th th Py Py C C 40 % dead shoots 30 20 10 0 % % 0% 5% 75 50 l5 l7 m m ro ro hiu hiu nt nt t co Py co t Py

P. phragmitis: The Role of Flooding Events 3. plants clipped before flooding to 6 or 12cm above soil line, 4 weeks 14 Mean regenerative shoot length, after 4 wks. 12 10 8 [cm] 6 4 a b a b 2 0 12 6 2 l6 l1 m tro m tr o iu iu on th on th Py C Py C Plant death, after 4 wks.: Control 6: 0 Control 12: 0 Pythium 6: 36% Pythium 12: 40%

P. phragmitis: The Role of Flooding Events 3. plants clipped before flooding to 6 or 12cm above soil line, 4 weeks water level 12 cm water level 6 cm Nechwatal et al., 2008 control Pythium control Pythium

P. phragmitis: The Role of Flooding Events flood Schmieder et al., 2002: Limnologica 32, 131-146 Mean water level 1951-2000 - Reed damage shown to be related to flood duration, time and depth - High susceptibility of submerged leaves to P. phragmitis - No damage in the absence of the pathogen P. phragmitis as a contributing factor in „flood-induced reed decline“

P. phragmitis: The Influence of Temperature growth rate 35 30 25 20 mm/ d 15 10 5 0 Straile et al., 2003: Limnol. Oceanogr. 48, 1432–1438 6 15 19 25 30 33 37 40 temperature [°C] 10 20 leaf necrosis size zoospore production Nechwatal et al., 2008: Hydrobiologia 613, 109-115 8 No. of infected bait ends 15 Lesion length [cm] 6 10 4 5 2 0 0 15 18 20 25 15 20 25 Temperature [°C] Temperature [°C]

P. phragmitis: The Influence of Temperature 30 young leaves flooded wind-bent, mature plants flooded Logger 4 TÜ Logger 8 Ü 25 Logger 1 T Logger 2 T Logger 3 T 20 Logger 6 Ü °C 15 10 5 0 August August August Nov Nov Nov Juni Juni Juni Juli Juli Juli März März März Dez Dez Dez Jan Jan Jan Jan April April April Sept Sept Sept Okt Okt Okt Mai Mai Mai Temperature logger data 2005 (littoral water and sediment) Mean temperature above 15°C ≈ mean highest lake water line (June – Sept.) optimum infection conditions

Flooding events and rising water temperatures increase the significance of the reed pathogen Pythium phragmitis - Pythium phragmitis as an aggressive pathogen of common reed - seedlings as well as mature leaves are susceptible - negative impact of flooding on reed only in the presence of the pathogen - flooding periods often equal periods of optimum temperature for the pathogen - optimum infection conditions - loss of plant vigour - losses in reed belt area - symptoms of reed decline -`climate change`: effect on flooding events (earlier in the year – younger plants!) -`climate change`: temperature effect on pathogen (growth, sporulation, virulence)

Thank you … ‚Littoral Zone of Lake Constance‘ The role of fungi during development and decay of reed (Phragmites australis)

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