Correlation of female indices from virulence assays on inbred lines and field Populations of Heterodera glycines

A lack of diversity and durability of resistant soybean varieties complicates management the soybean cyst nematode (SCN), Heterodera glycines exemplified overdependence on the PI 88788 source of resistance. Of interest is the effect of adaptation of a SCN population to it source of resistance oil its subsequent ability to develop on others. Female indices (FI) from virulence assays (race, HG Type and SCN Type tests) for SCN Field populations and inbred lines were analyzed. Female indices on PI 88788, PI 209332 and PI 548316 were highly correlated, its were those PI 548402, PI 90763, PI 89772 and PI 438489B. Previous studies on resistant SCN-infected soybean roots indicated that the cellular resisitance response was similar within these two groups of soybean genotypes. In field populations, highly significant correlations were also found between FI oil 111 88788 and 111 548,102 and those on PI 89772 and PI 437654. In Inbred fines, FI oil 111 4.17654 were correlated with PI 90763 and PI 438189B. To avoid further adaptation, rotation of cultivars with resistance from these groups should be carefully monitored, including those from the most promising source of resistance , PI 437654, such as CystX. In a separate test, 10 soybean varieties developed from CystX were tested against HG Type 0, AG Ty 2.5.7 and HG Type 1-7. Female development occurred in all tests but one. Although identification and deployment of unique is needed, management strategies to prevent and detect adaptaiion should be emphasized.