Audpc

AREA UNDER PROGRESSIVE CURVE

1. WELCOME

2. Contents: Introduction Why we use ? How to calculate AUDPC ? Advantages of AUDPC rAUDPC Conclusion References

3. How plant pathogens affect their hosts ? Effects on host physiology Effects on host development Effects on yield quantity Effects on yield quality

4. Time Disease intensity Time Yield Loss prediction For making decision that need of disease management (cost/effective calculations ). For identifying the time when the control is needed and assisting to develop effective management procedures . To know the level of resistance of cultivar against disease Why we need to evaluate diseases or assess yield loss?

5. Methods for evaluating disease Horsfall-Barrant Scale: a numeric value are assigned to the plant according to the percentage of leaf area infected by the disease. Direct Estimation: Estimate percentage of disease severity directly.

6. Evaluation of diseases or quantification It is one of the most important tasks and usually more difficult to perform. A adequate evaluation method should give exact, accurate and reproducible results Bulky and Laborious to maintain the data.

7. Area under disease progress curve (AUDPC)

8. Introduction The area under the disease progress curve ( AUDPC) is a useful quantitative summary of disease intensity over time, for comparison across years, locations, or management tactics. The most commonly used method for estimating the AUDPC, the trapezoidal method, is to discretize the time variable (hours, days, weeks, months, or years) and calculate the average disease intensity between each pair of adjacent time points (Madden   et al.  2007 ).

9. We can consider the sample time points in a sequence   { t i }, where the time interval between two time points may be consistent or may vary, and we also have associated measures of the disease level { y i }. We define   y (0) =  y  as the initial infection or the disease level at t = 0 (i.e., the first disease severity observation in our study). A( t k ).

10. Procedure for Computing the AUDPC SL NO NO OF DAYS PERCENTAGE OF DISEASE INCIDENCE 1 20 5 2 40 15 3 60 30 4 80 40 5 100 45

11. % of DI No of Days

12. % of DI No of Days

13. No of Days % of DI

14. AUDPC is estimated by: Where, n = total number of observations, yi = injury intensity (usually incidence in crop health data) at the i th observation, t = time at the i th observation.

15. Result and Interpretation Audpc = (0+5/2)*(20-0)+(5+15/2)*(40- 20)+(15+30/2)(60-40)+(30+40/2)*(80- 60)+(40+45/2)*(100-80) AUDPC=2250% AUDPC estimates the area under the disease progress curve. This value is expressed as % Highest values will correspond to more susceptible varieties and lowest values will correspond to more resistant varieties.

16. Advantages and Disadvantages The AUDPC is simple to assess because it uses multiple evaluations and does not need data transformation. It is very useful to carry out comparative analysis among varieties, genotypes or treatments in the same experiment and in the same crop season . AUDPC is that it cannot be used to compare results from different experiments . The values are not comparable for different seasons

17. How to measure resistance to LB AUDPC : has been used for a long time as a single measure to quantify the amount of disease (LB ), But we can not compare the AUDPCs of a clone in different locations , so we seek standardized measure called relative AUDPC ( rAUDPC ) rAUDPC : is calculated dividing the AUDPC of clone by AUDPC maximum potential.

18. The scale of susceptibility : Late blight is a polycyclic disease because the causal agent is able to reproduce and re-infect other plants in the same crop season. In 2009 Dr. Forbes et al., established a scale of susceptibility to LB using the numbers 1 to 9 . This scale allows us to compare resistance of a clones in different years and locations . This scale from 1 to 9 (resistant to susceptible) , gives numbers that are easier to remember and interpreted

19. Evaluation of late blight resistance To evaluate resistance of particular genetic material AUDPC The assessment of this parameter is based on the percentage of leaf area affected by late blight, which is determined visually and registered several times during the occurrence of the epidemic .

20. Assessment of AUDPC, a Microsoft Excel example Evaluations of the percentage of diseased foliar area corresponding to each genotype according to the date of evaluation should be recorded. Number of days after planting in which evaluation was per formed must also be recorded. In the example, nine varieties (a, b, c, d, e, f, g, h, and i ) were evaluated at 7, 14, 21, 28, 35, 42 and 49 days after planting . Place the cursor over cell I4, which corresponds to clone “a” area, and calculate the AUDPC by using the following formula: = ((C4+B4)/2)*($C$3-$B$3)+((D4+C4)/2)*($ D$3- $ C$3)+((E4+D4 )/2 )*($E$3-$D$3)+((F4+E4)/2)*($F$3 $ E$3)+((G4+F4)/2)*($ G$3 - $F$3)+((H4+G4)/2)*($H$3-$G$3) Press ENTER, and the AUDPC value “2765.00” will be displayed in cell 14 Copy cell I4 to the other cells (I5 to I12) and press Edit. Select PASTE SPECIAL, select FORMULAS and click OK. Values of AUDPC will be displayed in every copied cell

21. Results can be shown in graphics

22. The relative AUDPC ( rAUDPC ) should be used to compare data from different experiments. This value is better than AUDPC it may introduce SOME BAIS as when comparing experiments. To calculate the rAUDPC divide the AUDPC by N, where N=( The total number of days between the first and last evaluation) multiply by100 .

23. Considerations in evaluating resistance Evaluations of the percent of leaf area blighted must be initiated at the beginning of the epidemic . Time intervals for registering should not be long ; ( 1 week) if climate conditions are favourable to disease development . Evaluations should stop when susceptible genotypes are near total destruction . Since susceptible materials cannot get more infected, the more resistant ones will tend to catch up . The date of each evaluation must be recorded .

24. Uses of the AUDPC models The AUDPC models are used in both broad-leaf and cereal crops . In most cases, a very good relationship exist between AUDPC values and yield. The AUDPC models are used mainly for “after-season” loss assessment .

25. Conclusion Statistical models have been used extensively for summarizing and comparing plant disease epidemics. AUDPC was used to illustrate models and to summarize disease progress over time, in terms of population growth models and disease progress in a locations. AUDPC will help for developing methods to manage plant disease, such as developing forecasting models to .. Selecting an optimal planting date to reduce disease impacts To select the planting material . Determining the optimal time to apply a fungicide spray . OR To control disease in upcoming days.

26. References ARPN Journal of Agricultural and Biological Science DISEASE PROGRESS CURVES IN THE RICE BLAST PATHOSYSTEM COMPARED WITH THE LOGISTIC AND GOMPERTZ MODELS -N. K. Mohapatra Google.com

27. THANK YOU……