Genetic variability among and within races of Heterodera glycines Ichinoheassessed by RAPD markers

Heterodera glycines Ichinohe, the soybean cyst nematode (SCN) was detected in Brazil in 1992 and since then it has been causing losses to Brazilian so ybean crop yields. SCN populations have great genetic diversity which makes it difficult to manage this disease. The objectives of this research were to investigate the genetic variation of 16 SCN populations sampled in middl e western and southeastern Brazil, utilizing random amplified polymorphic D NA (RAPD) techniques, and to establish useful and specific RAPD markers for SCN race 3. RAPD markers demonstrated genetic variability among and within SCN populations, and they could be used for monitoring nematode population dynamics. The OPA-07 primer was a reliable molecular marker for race 3, wh ile electrophoretic profile analysis of DNA fragments amplified with OPA-10 primer detected slight variation within those populations identified as ra ce 3. The SCN population from Chapadao do Ceu, GO - sample 2 - was the most genetically distant from the other populations.