Dear Eman Khalaf is the hypersensitive response appeared in cucumber leaves resulted from powdery mildew or from the endophytic bacteria? have you got control with out powdery mildew infection (just inoculated with(endophytic bacteria)?. Thank you

Have you looked at the lesion under a dissecting scope?  If the powdery mildew is involved in the brown lesion, you will see mycelium on the surface, even if it is not sporulating.  A hypersensitive response to the mildew will only take place if a haustorium is triggering it.

Please, take a look on the attached photo and let me know. Thanks for sharing knowledge

I don't think it is due to neither pathogen nor endophyte interaction as I performed other trials using the same solutions and conditions without experiencing this problem.

I spent many years rating cucurbit leaves for powdery mildew!  I can't possibly say what that lesion is; it could be something completely unrelated to your experiment.  I see your mildew colonies on that leaf, small and clearly delimited.  I think you should exclude such leaves from your analysis.

Much thanks. Also, I have a new greenhouse trial and I found some foliar symptoms developed in three treatments. I think it is a disease. Also, do you have any idea if lactic acid bacteria can change the pattern or the color of the leaf? I will attach the photos 

Selected photos

Dear Eman 

The photos you displayed are not shown any powdery mildew symptom, it is also seems like downy mildew infection. You have to show us the lower surface of cucumber leaves that should reveal the conidiophores, mycelium and conidiospores, otherwise, this is not powdery mildew infection. I attached cucumber leaves infected with powdery mildew infection (upper and lower surfaces) 

Thank you

I know this is not powdery mildew infection and it is an extra infection I experienced in some replicates during the greenhouse trial. 

If your experiments with powdery mildew disease, I have a long experience with this disease and many research papers were published in different journals. so you feel free to ask me about this disease.

Have you examined the downy mildew? it could be Pseudoperonospora cubensis

 You mean molecular identification of the pathogen?

I doesn't  matter whether molecular or morphological identification

I recommend Eman's answer

Best Regards