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Suppression of Fusarium Patch by Phosphite in Cool Season Turfgrasses

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Suppression of Fusarium Patch by Phosphite in Cool Season Turfgrasses Centre for Research in Biosciences Suppression of Fusarium patch by Phosphite in cool season turfgrasses John Dempsey BSc(Hons) Centre for Research in Biosciences, Bristol, UK Greenkeeper since mid 1980’s Course manager at Curragh Golf Course since 1993 BSc in Turfgrass science – Myerscough college, UK Currently carrying out postgraduate research for a PhD in turfgrass pathology – The mechanism by which phosphite reduces susceptibility to Microdochium nivale Todays talk- • Phosphite - what is it, its history and current usage • Does phosphite suppress Microdochium nivale in turfgrasses? • By what means does suppression occur? • Microdochium infection process • Turfgrass responses Two components of this research Microdochium nivale Phosphite What is Microdochium nivale? Ascomycete fungus - Fusarium patch or Pink snow-mould Most common pathogen in cool-season turfgrass Microdochium active on Poa annua Microdochium active on turfgrass Reliance on fungicides- Expensive Inhibition of beneficial organisms Legislative controls Scope for alternative means of disease control Phosphite is one possible method Phosphite? Form of Phosphorous (P) a major nutrient of plant growth Taken up as Phosphate - Phosphoric acid (H3PO4) Phosphite - Phosphorous acid (H3PO3) Phosphite use • Phosphite derived from Phosphorous acid – (H3PO3) pH 2.2 - has to be modified with an alkali salt to usable pH • First used in 1980’s - Rhone- Poulenc fosetyl Al (aluminum tris (O- ethyl phosphonate)) • Potassium hydroxide (KOH) - Forms Potassium dihydrogen phosphite (KH2PO3) or dipotassium hydrogen phosphite (K2HPO3) Potassium phosphite Ammonium Hydroxide, Magnesium phosphites and Calcium phosphites Phosphite not metabolised in plants Phosphite should not be applied to plants in sub-optimal phosphate conditions Phosphite only converts to phosphate by means of soil organisms Bacteria can metabolise Phosphite to Phosphate - Escherichia coli, Pseudomonas stutzeri, Alcaligenes faecalis and Xanthobacter flavus Half-life for oxidation in soil is approximately 12–16 weeks (Adams and Conrad 1953). Suppresses phytopathogens Pythium and Phytophthora Oomycete pathogens Anthracnose Microdochium in cereals Improved turf quality No research into Phosphite and Microdochium nivale Performance of Phosphonate Fertilizers and Fungicides on Pythium Blight Development on a Perennial Ryegrass Golf Course Fairway. — 2007. Horvath, B.J. and D.S. McCall, Virginia Tech University In vitro mycelial growth rate of Microdochium majus measured on PDA amended with potassium phosphite solution – Hofgaard et al 2010 BSc Study at Myerscough Dr. Andy Owen • Establish Agrostis stolonifera swards • Apply a range of phosphite treatments • Assess treated and untreated controls Growth Turf quality Disease occurrence Methodology Agrostis stolonifera established in Greenhouses Trial plots Treatments • 0.35g/m2 Phosphite • 0.525g/m2 • 0.70g/m2 • 0.35g/m2 Phosphate • 0.525g/m2 • 0.70g/m2 Control • Nil Applied every 3 weeks - Replicated 6 times Assessments - Growth Shoots Crowns Collected dried and weighed Results - shoot Growth Results – shoot and crowns Control Phosphite December 2008 Assessments –Turf Quality Turf quality- greenhouse and trial plots Visually assessed 2 weekly intervals Scale of- 1 – 10 Results – Turf quality Turf quality –Trial plots Assessments –Disease Occurrence Disease assessments- Greenhouse and trial plots Visually assessed 2 weekly intervals Rated on percentage of disease occurrence Results –Greenhouse Results –Trial plots Control Phosphite January 2009 Phosphate Phosphite November 2008 Control Phosphite December 2008 Phosphite treated plants – January 2009 Control plants – January 2009 Conclusions of the Myerscough Study Not metabolised Improved Phosphite turfgrass quality treatment- Reduced disease European Turfgrass Society 2nd Conference Angers, France 2010 Centre for Research in Biosciences PhD Research objectives - Phosphite reduce Microdochium? Means of reduction? Field trials Laboratory studies Curragh golf course –field trials Three turfgrass species • Agrostis canina canina • Agrostis stolonifera • Poa annua Range of phosphite treatments and assessments Published Trials – Griggs and Turfcare PK Plus 20L ha-1 3- -2 (PO3 0.37g/m ) -1 PK Plus 20L ha +Ultraplex 10L ha-1 Trials running since Sept 2010 Chipco 20L ha-1 Treatments applied bi-weekly Iprodione 20L ha-1 Disease incidence assessed monthly -1 Chipco 20L ha -1 +PK Plus 20L ha NPK Control (3:7:18 20l ha-1) Untreated Control Disease Assessments –Poa Plots Poa annua plots - mean disease incidence over two years (n=5), letters indicate significant differences at p< 0.01 Agrostis stolonifera plots mean disease incidence over one year (n=5), bars represent standard error, letters indicate significant differences at p< 0.01 Agrostis canina canina plots Agrostis canina canina plots mean disease incidence over two years (n=5), bars represent standard error, letters indicate significant differences at p< 0.01 Mean disease incidence over two years (n=5), bars represent standard error, letters indicate significant differences at p< 0.01 PK Plus Chipco Chipco NPK Control Control +Ultraplex +PK Plus Assessment of Turf quality – 2010 to 2012 Turf quality average over two years 10.00 P. annua A. canina canina 9.00 a a a a a a 8.00 7.00 6.00 b 5.00 b b b 4.00 b b 3.00 2.00 1.00 0.00 PK Plus Pk Plus + Ultraplex Chipco Green Chipco Green + PK NPK control Control Plus Agrostis canina canina plots – January 2012 Agrostis canina canina plots – January 2012 Poa annua plots – January 2011 Poa annua plots – October 2011 CONTROL PHOSPHITE Poa annua plot 5 – Phosphite Poa annua plot 16 - Control Agrostis stolonifera plot 7 – Phosphite Agrostis stolonifera plot 5 – Control Agrostis canina plot 9 – Phosphite Agrostis canina plot 3 - Control Field trial conclusions • Sequential applications of phosphite significantly reduced Microdochium nivale incidence • The addition of phosphite to iprodione significantly enhanced suppression of Microdochium nivale • Significant improvement in turfgrass quality Means of suppression Direct • Inhibits pathogen Indirect • Stimulates plants defences Combination of both In Vitro Study- Assess the effect phosphite has on the mycelial growth of Microdochium nivale Microdochium propagated from infected turfgrass Grown on and used for in vitro study To assess inhibition of mycelial growth Amended growth media Amended PDA Range of phosphite and phosphate From 0.5 μg/ml to 1000 μg/ml Compared with unamended controls Control + 4 days Phosphate - 100 μg/ml + 4 days Phosphite - 100 μg/ml + 4 days Mycelial Growth on Amended PDA Phosphite 100µg/ml Phosphate 100µg/ml Control Hyphal morphology Unamended 75µg/ml Phosphite Hyphal morphology Unamended 75µg/ml Phosphite Fungicide or Fungistat? Does phosphite kill the pathogen? Or just inhibits the growth? Immersed the mycelium in a range of phosphite and phosphate concentrations for 10 days Extracted, washed and placed them on fresh PDA Observed the effects on re-growth Mycelial growth after immersion for 10 days M. nivale mycelial growth - four days post inoculation 100 90 80 70 mm - 60 50 40 Radial Radial growth 30 20 10 0 Control 50µM 100µM 500µM 1mM 5mM Control PO4 PO3 In vitro conclusions • Inhibits mycelial growth and conidial germination • Disrupts hyphal morphology In the plant – • Slows the growth of the pathogen • Causes release of stress metabolites • Allows for increased time for the plant to initiate defence responses What happens when phosphite is applied to turfgrass? • Measure assimilation rate • Track translocation Targets • Determine accumulation amounts • Assess the fate • Treat turfgrass • Collect samples Methods • Six week period • Analyse using HPIC ppm Phosphite accumulation in Agrostis stolonifera 6000 4889 5000 4205 3876 4000 3334 3193 3000 2561 2000 1000 715 639 492 393 376 338 265 111 120 116 126 0 55 0 0h 1h 6h 12h 24h 48h 1wk 2wk 4wk 6wk Time post-application Leaf phosphite Root phosphite HPIC Results –Phosphate ppm Phosphate accumulation in Agrostis stolonifera 12000 10000 8000 6000 4000 2000 0 0h 1h 6h 12h 24h 48h 1wk 2wk 4wk 6wk Time post-application Leaf phosphate Root phosphate Leaf phosphate -Control Root phosphate -Control HPIC Results –Phosphite +Phosphate Long term results – 4 weeks post application ppm 1250 ppm in first study 1600 1493 1400 715 ppm in first study 1200 1104 1055 1000 802 800 600 338 ppm in first study 400 183 200 156 0 Leaf Crown Root 6 months 4 wks pa 12 months 4 wks pa Samples taken – January and July 2012 Long term results – 8 weeks post application ppm 500 450 400 350 300 250 200 150 134 119 126 100 42 44 50 34 0 Leaf Crown Root 6 months 8 wks pa 12 months 8 wks pa Samples taken – January and July 2012 HPIC Conclusions • Phosphite is rapidly assimilated by turfgrass • Translocates throughout the plant • Accumulates in the leaf tissues • 3-4 week application period maintains levels within the leaf • Long term applications show metabolic rate effects accumulation period in tissue • Slight increase in meristematic areas • Effect on soil P amounts yet to be calculated Does Phosphite enhance the defence responses in infected turfgrass? Need to understand the infection process and turfgrass responses Using pot samples and infected greens Fluorescent microscopy and stains • Inoculum in the soil – conidia, mycelium • Infection first in the crown and sheath area • Moves to the leaf and enters plant through stomata • The plant recognises the pathogen, this leads to induction of defence responses • Hydrogen peroxide • Nitric oxide
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