Hi Ahmed,

Did you use a rating scale for leaf turgidity and leaf color? When did you score frost stress on the leaves? Was it at specific days after treatment application or days after transplanting/sowing. I am attaching a pdf file which I prepared for a training on how to compute area under injury progress curve. In your case, the x values are the ratings for leaf turgidity or leaf color and the y values are days after treatment application or transplanting/sowing. I think that your computed values should be termed as area under leaf turgidity progress curve or area under leaf color progress curve.

Cheers,

Nancy

Hi Nancy

Thank you very time for  the info. Your  file, indeed, the best source I have read to know how to get AUDPC "Thanks again". As I understood from your file , we have two scores "score of trait" and "score of days number". But in my case, instead of "scores of days number" I have treatments which are freezing temperatures. Because, freezing temperatures had the effect of the  symptoms (the symptoms of frost increases by the increasing of freezing temperatures" in leaves. I applied three freezing temperatures -16, -18, 19 for three consecutive nights (one night for each treatment. So according to your great explain

Treatment        Loss of torridity

0                         0

-16                      2

-18                       6

-19                       9

So, here I have mins (-), should I deal with positive value? and if so I will get huge differences in treatment (16, 2, 1). But in your example I have noticed the number of  days was 20 (20-0, 40-20,.. and so on)

What is your recommendations?

You can get the curve under increasing freezing temperature by the way of calculating the surface below each midpoint of the given temperature.

between 2 point of freezing temperature (dt) the surface will be: (Somme of loss of torridity /2)x dt and you each data calculate between 2 freezing point.

result will be area under loss of torridity = [((0+2)/2)x16] + [((2+6)/2)x2]+[((6+9)/2)x1]

Thank you very much for confirming what I expected ....

Hi Ahmed,

I think that you should  have AULT values for each treatment.  How many times or when do you assess loss of torridity for each temperature? I assume that for each temperature, you assess torridity at different periods.

Best,

Nancy

Hi Nancy

The freezing temperature was applied in the night and I visually scored the symptoms of frost (loss of leaf turgidity and loss of leaf color) during the day and before the next night. As I described above. So I give one score for leaves in each treatment.

You can use the same principle for AUDPC. 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). We can consider the sample time points in a sequence {ti}, where the time interval between two time points may be consistent or may vary, and we also have associated measures of the disease level {yi}. We define y(0) = y0 as the initial infection or the disease level at t = 0 (i.e., the first disease severity observation in our study). A(tk), the AUDPC at t = tk, is the total accumulated disease until t = tk, given by . To illustrate this concept, the exercise below shows the rectangular area Si as the increase in accumulated disease during the time interval from ti-1 to ti, S1 = A1 and Ai = Ai-1 + Si, i ≥ 2.