Race Comparisons of Heterodera glycines Using Crossed Immunoelectrophoresis.

Four races of soybean cyst nematodes (SCN), Heterodera glycines, have been described in tile United States (2), and many other variations have been demonstrated (4). T h e races have been reported to be morphologically and serologically identical (5). However, since the races interact differently when inoculated to different cultivars of soybeans, there should be some biochemical differences. This study was nndertaken in an a t tempt to identify differences between the different races of SCN. Nematodes were reared on 'Lee' (Race 3) or 'Pickett ' (Races 2 and 4) soybean cultivars in a greenhouse. White females were sieved out by the roil ing and sieving method, separated from extraneous debris, and maintained frozen unti l used. T h e packed cysts were homogenized in a Teflonglass homogenizer in two volumes of distilled water and centrifuged at 700 Xg for 15 rain. T h e supernatant (about 10 mg protein/ml) was withdrawn and used as a source of antigens. Four rabbits were injected subcutaneously with 0.4 ml of supernatant mixed with an equal volume of Freund's Complete Adjuvant. Injections of antigen in Freund's Incomplete Adjuvant were continued every few days for one month until distinct precipitin bands were found with crossed immunoelectrophoresis. An injection of antigen was given one week prior to any additional antiserum collections. Blood obtained from each rabbit 's ear was allowed to clot, centrifuged at 600 ×g for 10 rain, and the antiserum withdrawn and frozen. Crossed immunoelectrophoresis was run in a 1% agarose gel in a barbital-glycine/ Tris buffer, pH. 8.8, ionic strength 0.08 (1) using 5 or 10 tA of each antigen solution. In the second dimension, the separated