How to calculate the quantification of qPCR to the equivalent of the number of nuclei in fungi?
From your comment:


  "As few as 148 fg of Verticillium dahliae DNA were detected and quantified (through qPCR), which is equivalent to five nuclei". How is possible to make this convertion?


The Verticillium dahliae JR2 genome is 36.2 Mb.  Assuming this organism is haploid and dsDNA has an average mass of 660 g/mol per base pair, that means the molar mass of the genome is 2.40 × 1010 g/mol.  Therefore, 5 nuclei will contain 8.30 × 10-24 mol of your genome.  Multiplying the molar mass by the number of moles gives us a mass of 1.99 × 10-13 g, or 199 fg, which is close to your cited value.