Measuring plant response to virus infection and water stress

Transcription

1 Measuring plant response to virus infection and water stress van den Brink RC, Austin PT, Arthur KR, MacDiarmid RM, Hedderley DI Valmonte G, Immanuel T, Fagaloa-Time M, Higgins C

2 Introduction can we quantify symptom severity?

3 Data experiment overview 6 viruses CMV PVA TRSV TuMV TVCV TYMV 3 host species Arabidopsis thaliana (wild type + t-dna lines) Nicotiana benthamiana Nicotiana glutinosa 9 experiments (PFR + AUT) 830 plants 26,000 observations

4 Data a wide range of plant variables measured Petiole length Plant or 1º inflorescence height Branch or 2º inflorescence length Internode length Number of symptomatic leaves (virus- or drought-affected) Virus symptom severity score Leaf width Plant rosette diameter Fresh weight (28dpi) Dry weight (28dpi) Number of leaves Number of branches Number of flowers

5 Composite indices for growth, health, reproduction 1. Growth variables Vegetative Vigour Index Petiole length (mean, n=5) Plant height Branch length (mean, n=5) Leaf width Fresh weight (28 dpi) Shoot dry weight (28 dpi) 2. Symptom variables Plant Health Index Virus symptom score Drought stress score 3. Reproduction variables Reproductive Effort Index Leaf count Visible branch count Flower count

6 Composite indices measuring symptoms 1. Growth variables Vegetative Vigour Index Petiole length (mean, n=5) Plant height Branch length (mean, n=5) Leaf width Fresh weight (28 dpi) Shoot dry weight (28 dpi) 2. Symptom variables Plant Health Index Virus symptom score Drought stress score 3. Reproduction variables Reproductive Effort Index Leaf count Visible branch count Flower count

7 Calculations Vegetative Vigour Index 1. Growth variables Petiole length Plant height Branch length Leaf width Fresh weight (28 dpi) Shoot dry weight (28 dpi) where x xmax = variable measuring plant size j = number of variables used = expected maximum value for variable (species-specific)

8 Calculations Plant Health Index 1. Growth variables 2. Symptom variables Virus symptom score Drought stress score where z zmax = quantitative scores of plant health l = number of variables used = expected maximum value for variable

9 Calculations Reproductive Effort Index 1. Growth variables 2. Symptom variables 3. Reproduction variables Leaf count Visible branch count Flower count where y ymax = variables for reproductive development k = number of variables used = expected maximum value for variable

10 An example using indices reduces complexity 8 variables 2 treatments 3 indices 2 treatments

11 An example taking ratios simplifies things further DPI

12 Result Response indices make analysis simpler 8 variables 2 treatments 3 index ratios + Can include variables specific to any plant + Indices can be calculated in a spreadsheet + Allows comparison across researchers & sites

13 Application comparison across experiments How can we use our indicies? 1. Comparing one host with different viruses 2. Comparing two hosts & two viruses 3. Including response to drought

14 Case 1 comparing Nb with different viruses Nicotiana benthamiana 5 viruses 3 experiments Plant Health Index

15 Case 2 comparing two hosts & two viruses At +CMV Nb +TuMV 2 experiments Veg. Vigour Index, as a ratio to the control

16 Case 2 a similar effect on host reproductive effort At +CMV Nb +TuMV 2 experiments Repro. Effort Index, as a ratio to the control

17 Case 3 including response to drought Ng +/-TRSV, tolerance to two periods of water stress Plant health before imposing drought

18 Case 3 including response to drought Ng + TRSV, tolerance of two periods of water stress Plant health over whole time-course

19 Conclusion the value of composite indices It s a combined approach Uses symptom observations and plant measurements Complements molecular approaches And a tool for quantitative hypotheses How much of an effect does genotype have? How strongly do viruses influence plantenvironment interactions?

20 Credits Data collection Gardette Valmonte, Tracey Immanuel, Mariah Fagaloa-Time, Kieren Arthur, Roy van den Brink Data preparation Paul Austin Index development Paul Austin, Duncan Hedderley Statistical analysis Duncan Hedderley Project leader Kieren Arthur Research direction Robin MacDiarmid Colleen Higgins

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