Molecular characterization of soybean cyst nematode populations with different parasitism index to the Hartwig cultivar

Recently, a new race of soybean cyst nematode (SCN) (Heterodera glycines) w as discovered, which breaks the resistance of cultivar Hartwig, resistant t o all known races of SCN. This population was obtained from soybean plants collected in the Sorriso county, state of Mate Grosso, Brazil, and is chara cterized as race 4. To verify if this isolate was different from others cla ssified as races 4 and 9, their genetic diversity was analyzed by using the RAPD technique. Nine populations of SCN were analyzed, and only four popul ations were able to parasitize soybean plants cultivar Hartwig. Based on th is study, it was verified that the populations that break Hartwig resistanc e were different from the other populations. Based on cluster analysis, the populations were separated into three groups. Race 4 populations were plac ed in the first group, while the race 9 population was placed in the second group and those capable of breaking cultivar Hartwig's resistance were pla ced in group three. This work confirms that the SCN population found in Sor riso is different from other isolates classified as race 4, and was called race 4(+).