For the samples with smear, it looks like you are using too much of DNA as template. Reduce the amount of DNA to ~20-30 ng in a 25 µl PCR reaction. For the samples/wells which did not give smear, they were not amplified, might be due to some sort of inhibition.

I think that the smearing is typical of post pcr contamination getting into your reaction from previous pcrs. Tiny amounts of contamination amplify very well and huge amounts ( 1000 times more in every 10 cycles) and eventually the amplified product self anneals and generates longer concatamers of product.The contamination could be in the pipettes,in dust on working areas or on plasticware. Are you running no template controls in your pcr assays and do you ever get these effects in the wells that have no added sample?

You can get a similar effect when only one primer is working and extending to random lengths but the smear is not usually as strong as yours but check the sequence of both primers is correct just in case but run 3 or 4 no template controls to see what they look like.

As Abhijeet Singh says it does look like degraded genomic dna so also check the amount of dna that you are adding

What is your template dna and how much are you adding per reaction?

Dear Paul and Abhijeet sir,

I am taking 2 ul genomic DNA of mycobacterium in 50ul Reaction having 24ng/ul concentration. also, I have used 1ul (20ng/ul conc.) of a previously amplified PCR product as a template. but the result was the same.

If you are re amplifying then you must heavily dilute the amplified template...use about 1ul of a 1:1000 dilution and only run 15-20 cycles. All amplified product is template so a tiny amount is a huge number of copies for pcr template.

What do your no template controls look like please?

Thank you so much Mr. paul and Mr. Abhijeet sir, today i was changed genomic DNA and diluted it and used in pcr reaction mixture and surprisingly i got the result.

Thank you so much..,,🙏