SEASONAL BIOCHEMICAL-CHANGES IN EGGS OF HETERODERA-GLYCINES IN MISSOURI

Changes in the carbohydrate (glucose, trehalose, and glycogen) and tot al protein contents of eggs retained with Heterodera glycines cysts we re monitored monthly in a field microplot experiment conduced from Mar ch 1993 to March 1995. Treatments included two near-isogenic lines of soybean cv. Clark differing for date of maturity, and one corn hybrid. The soybean lines were planted in microplots infested with H. glycine s at a high average initial population density (Pi) (23,810 eggs/100 c m(3) soil). and the corn was planted in microplots infested at high (2 4,640) and low (5,485) Pi. Soil temperatures at 15 cm depth and rainfa ll were monitored. Carbohydrate contents varied in the same pattern, w ith the highest levels measured before planting (may) and after harves t (October) in both years. Neither Pi nor soybean isoline had an effec t on any measured response, but the carbohydrate contents of eggs from corn and soybean microplots differed during the overwinter (October-M ay) periods (P < 0.0001). Trehalose accumulation was negatively correl ated with soil temperature (r = -0.78 and r = -0.84, P = 0.0001, July through November 1993 and 1994, respectively), which reflects its role as a cryoprotectant. In contrast to the pattern for carbohydrates, to tal protein wa slowest before planting and after harvest, and highest (>20 mu g/1,000 eggs) June through October. Protein content was unaffe cted by plant cultivar or species. Protein and carbohydrate levels in H. glycine eggs showed seasonal changes that appeared to be primarily temperature-dependent.