Evaluation location: Arkansas, United States
Soybean seeds were germinated in flats of vermiculite, and single seedlings were transplanted at the cotyledon stage into 10-cm-diam. clay pots containing 500 cm 3 fine sandy loam (91% sand, 5% silt, 4% clay; < 1% O.M.). The soil in each pot was inoculated with ca. 1,000 vermiform reniform nematodes placed in three 1-inchdeep depressions. The R. reniformis population was from an Arkansas isolate obtained from a Jefferson County, Arkansas cotton field in 1986, maintained in a greenhouse on cotton cv. DP-50, and increased on soybean cv. Braxton for these studies. Greenhouse ambient air temperature ranged from 28 to 34?C. All test pots were watered twice daily (8 am and 4 pm) and fertilized once a week with soluble 20- 20-20 (N-P-K). Final nematode populations for each pot were determined by combining the soil (sieving, sucrose centrifugation extraction) and root (sodium hypochlorite shaker extraction) populations. A reproductive index (RI = final population/ initial population) was calculated for each entry.