The distribution of Heterodera glycine and Heterodera sojae was surveyed and charicterized with respect to geographical and spatial distribution in soybean field soils from Gangwon- and Chungchungbuk-do provinces, Korea.
In Gangwon-do Heterodera glycine was detected in one soil and both H. glycine and H. sojae in another soil out of 2 soils sampled from Hoengseong during harvest time(2017). During the growing season(2018) H. glycine was detected in 12 soils and H. sojae in 5 soils out of 53 soybean field soils.
In Chungcheongbuk-do, among 46 soybean field soils taken during the harvest time, Heterodera glycine was detected in 13 soils(32% of detection rate) and H. sojae was present in 3 soils(7.9% of detection rate). H. glycine and H. sojae co-existed in 2 soybean field soils.
Of soil samples collected during the growing season, H. glycine was detected in 14 soybean fields (30.4% of detection rate) and H. glycine and H. sojae co-exist in 3(6.5% of detection rate) soil samples.
The detection rate of H. sojae was significantly lower than that of H. glycine, and rates of soils that H. sojae and H. glycine were detected were 4.6% and 32.1%, respectively, that of H. glycine being 6 times higher than H. sojae in Chungcheongbuk-do. In Gangwon-do, the rates were 7.5% and 19.4% for H. sojae and H. glycine, that of H. glycine being about 2.5 times higher.
From soybean field samples collected during the harvest time, 5 families and 6 genera of Soybean cyst nematode were detected in 14 surveyed sites of Gangwon-do and 8 families and 10 genera in 29 sites of Chungcheongbuk-do. In samples from Gangwon-do genus Pratylenchus (7 sites, 50%) and genus Meloidogyne (4 sites) were dominant and subdominant genera, respectively, and in those from Chungcheongbuk-do Heterodera (12 sites) and Pratylenchus (11 sites) were shown to be dominant genera and Hoplolaimous (7 sites) was subdominant genus.
Genus diversity and dominancy of plant parasitic nematodes between soybean field soils with and without soybean cyst nematode in Gangwon- and Chungcheongbuk-do were not significantly different, but both groups had high dominance index and low diversity index, showing soybean fields supported high density of particular plant parasitic nematodes.
Relationship between soybean cyst nematodes and soil chemical properties showed low value of coefficient of determination and the density of soybean cyst nematodes tended to increase as pH and available phosphate content in soil samples increased. The soil texture of cyst-detected fields were mostly sandy soils which amount to about 60%. As the content of clay and silt increased, the density of soybean cyst nematodes tended to decrease, and as the sand content increased, the density of cyst nematodes tended to increase. Soybean cyst nematodes in Hongcheon showed contagious distribution pattern in specific area, and populations of soybean cyst nematodes from soils during the growing season and during the harvest time were similar to each other. The population of soybean cyst nematodes in soybean fields surveyed in Gangwon-do was low in almost all soil samples and was not detected during the harvest time.
In upland-cultivated soybean fields, as the higher contents of sand and silt generally resulted in the higher density of soybean cyst nematodes as compared to the lower density in paddy soybean fields soils with higher clay content, measures should be taken to diminish the number of cysts nematodes.