Abstract
Wainwright, L.L. and G.L. Tylka. 1995. Embryological development of Heterodera glycines on soybean cultivars of different maturity groups in Iowa. Journal of Nematology 27:523.
Embryogeny of Heterodera glycines was studied in 1994 on an indeterminate, maturity group (MG) II and a determinate, MG VII soybean cultivar in replicate H. glycines-infested field microplots. Plants were sampled every 10 days through the growing season beginning 32 days after planting. Females and cysts were dislodged from roots, and eggs were extracted, fixed in 3% formaldehyde, and stored at 4 C until analyzed for stage of development by flow cytometry. A maturity index (MI) was calculated by dividing the number of mature eggs containing vermiform juveniles by the total number of eggs in each sample. Vegetative shoot development of the cultivars was similar throughout most of the growing season, but the MG II cultivar began flowering about 50 days before the MG VII cultivar. MI of the egg populations was similar (P > 0.05) between cultivars at most sampling dates. Eggs recovered from both cultivars were mostly mature by late September, yet the MG VII cultivar remained actively growing. Two H. glycines generations likely occurred during the 123-day experiment.