A novel detection method for the soybean cyst nematode Heterodera glycines Ichinohe using soil compaction and real-time PCR

The primers SCN44f and SCN124r were designed for the quantitative detection of the soybean cyst nematode (SCN) Heterodera glycines using real-time PCR. An andosol naturally infested with SCN was put into a 100 ml core and compacted to various degrees, i.e. 0.93 to 1.4 g cm-3, using a manually-operated compactor. Then, DNA was extracted from the compacted soils as well as non-compacted soil (0.66 g cm-3) and used as templates for real-time PCR. Ct values were the lowest at 1.4 g cm-3, the maximum physical compaction of the andosol in the compactor, and the difference in the Ct values between compacted and non-compacted soil was four cycles at the largest, suggesting that 16 times more DNA derived from SCN was detected by the compaction. Then, different numbers (10 to 3,000) of SCN eggs were added to 20 g of a non-infested andosol and the soils were compacted to 1.4 g cm-3. There was a significant correlation (r2 = 0.8615, P < 0.001) between the Ct values and the number of eggs added. These results demonstrated that the present method using a combination of soil compaction and real-time PCR enabled rapid and sensitive quantification of SCN eggs in soil.