Agriculture Reference
In-Depth Information
Figure 10.18. Schematic diagram of a DNA hybridization procedure.
Figure 10.19. Schematic diagram of a polymerase chain reaction (PCR) procedure.
Polymerase Chain Reaction (PCR).
PCR seed health testing involves ampliication of a DNA
region of the pathogen genome that is unique to the target pathogen. Primers that consist of short single-
stranded DNA sequences deine the region (Fig. 10.19). The DNA of the pathogen genome is irst extracted.
DNA polymerase, deoxyribonucleotides and primer DNA are mixed in an appropriate buffer. The double-
stranded target DNA is irst unwound to produce single stranded templates; this is usually achieved by
heating. Primers then anneal to the templates and daughter strands are synthesized in the 5' to 3' direction.
Enzymatic ampliication goes through repeated cycles that can give one million copies of each target strand
in 20 cycles. The ampliied DNA is detected by southern blot electrophoresis. The sensitivity of the test for
