We want to check the effect on DNA due to infection of Plant Pathogen. What could be proper procedure to isolate DNA from an infected Plant? Is the procedure of isolation of DNA same for both healthy as well as disease Plants?
You say you want "to check the effect on DNA due to infection of Plant Pathogen". At the level of DNA you will not see any difference between infected or healthy plants. The DNA of the host is always there, independently if the plant is infected or not. (If the host has resistence genes, for example, these DNA is there before and after infection).
But what changes after infection is the pattern of transcription of DNA. That means that you have another pattern of messenger RNA before and after infection. And that means that you have to study the transcriptome before and after infection of the host. To study the transcriptome, you need RNA extraction.
I recommend you to read about changes of the transcriptme as much as you can (in the last 10 years a plenty of papers have appeared about this subject) to understand how does genetic of infected plants works. Which kind of genes are activated (= transcribed into mRNA) after infection? And to know which is the challange of working with RNA and transcriptome. I have attached a revue which gives an overview of the "effector" system between pathogens and plants. But please read more about transcriptome before you continue with this investigation line.
Thank You, Madam, for your valuable comments. I will read about transcriptome. You have talked about effect system, r gene of plant in infected plant corresponds with a gene of plant pathogen. I will have to focus on R/r genes which are vertical host resistance genes of Plants.
What do you mean by structural interface between algae and fungi?? Is not there any such kind of structural interface between plant pathogen and plants??