try young leaf first. Try CTAB method for extraction. About the tissue depends on how much quantity of DNA you want. For routine SSR and others 25 mg tissue is enough but if you want to do other works then you need a bit more 

1. How pure do you need for your DNA samples to be? Is it for a sensitive experiment later or just for a quick PCR to identify such as a transgenic gene?

2. I would suggest using leaf first as mentioned by Padder if you still have those plants. Potato tuber tissue contains a lot of starch which complicates genomic DNA isolation.

Dear Islam,

I have done DNA extraction for Kiwi fruit as follow:

You will need:

A kiwi fruit (or another fruit or vegetable of your choice), a peeler/knife, a fork, methylated spirit (chilled in a freezer for 30 minutes), a fine sieve or filter paper, a couple of bowls, salt, water, washing-up liquid, teaspoon, measuring beaker, a couple of glasses, a paper clip.

Instructions:

1. Put your alcohol in the freezer half an hour before you start the experiment.

2. Peel the skin off your fruit or vegetable. Discard the skin, and chop up and then mash the rest in a small bowl.

3. Mix 2g of salt with 100ml of water in a beaker and slowly add 5g of washing up liquid.

4. Add this mixture to your fruit and vegetable and continue mashing.

5. Place your bowl in a larger bowl or warm water for 15 minutes.

6. Strain your mix into a glass through a strainer.

7. Gently add the alcohol to your glass of kiwi DNA.

8. Use a paper clip to remove the DNA, which has appeared at the join between the two liquids.

 So, you may get an idea to extract DNA in potato as well.

Best regards,

Arshad Yaseen

Thank you everyone for giving a excellent idea of DNA isolation from potato. Actually, I was looking for methods of DNA isolation which could give me gDNA in a quick time with significant number of lines/genotypes at a time so that I can isolate DNA in a short time from huge number of genotypes.

You can use genogrinder for that it is very efficient and time saver. We normally use it in our lab. We can do 500 samples extraction in the single day itself.

http://www.labmanager.com/products-in-action/2012/11/the-2010-geno-grinder-?fw1pk=2#.VHhEf9KUdc0

Sir,

You can go with Qiagen company people who are doing multiple samples( around 250 at a time with good yield) . Recently we were tried install the machine here but we postponed it. Even for old insect specimens it worked well .However, you may give your samples to them who can do it for you. If you want to do in regular basis you may install the robotic machine at your lab on lease basis also. . It surely works..!!