LOCATION OF HETERODERA-GLYCINES-INDUCED SYNCYTIA IN SOYBEAN AS AFFECTED BY SOIL-WATER REGIMES

Locations of syncytia induced by the soybean cyst nematode (SCN), Hete rodera glycines race 3, were compared in roots of 'Essex', a susceptib le soybean (Glycine max (L.) Merr.) cultivar, at three soil water regi mes. The plants were grown in wet (- 5 to - 20 kPa), moderately wet (- 30 to - 50 kPa), and moderately dry (- 60 to - 80 kPa) autoclaved Cap tina silt loam soil (Typic Fragiudult). In the moderately dry soil, sy ncytia were found only in the stele, but in moderately wet and wet soi ls, syncytia occurred primarily in the cortex and occasionally in the stele. The location of syncytia in the cortical tissue of roots growin g in wet and moderately wet soils may account for the tolerance of sus ceptible soybean cultivars grown under well-irrigated conditions where there is less interference with water transport through roots. Cell-w all perforations and dense cytoplasm were characteristic of syncytial cells observed in root tissues of all treatments.