MACRONUTRIENT UPTAKE, TRANSLOCATION, AND TISSUE CONCENTRATION OF SOYBEANS INFESTED WITH THE SOYBEAN CYST-NEMATODE AND ELEMENTAL COMPOSITIONOF CYSTS ISOLATED FROM ROOTS

The soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is a maj or pest of soybeans (Glycine max L. Merrill) in the central and southe rn United States. Soybean cyst nematode causes stunted top growth, roo t pruning and symptoms of mineral element deficiency in soybeans. The objective of this study was to determine the effect of two selections of SCN (I selected on PI209332 and IV selected on PI 89772) on macronu trient uptake, translocation, and tissue concentrations of soybean and to determine the elemental composition of cysts isolated from roots. Soybeans were grown in plastic tubes in the greenhouse where the middl e one-third of the Hedge fine sand (Typic Udipsamment) contained 0, 25 ,000, or 50,000 SCN eggs. After 35 days, plants were harvested and tis sue nutrient element concentrations were determined. Plants infested w ith both SCN selections were smaller and had much less root volume tha n controls. Dry weight of each plant tissue decreased as SCN populatio n was increased. Root concentration of potassium (K) and magnesium (Mg ) was decreased, whereas root calcium (Ca) and phosphorus (P) concentr ations were increased with SCN treatments. Leaf Mg and Ca concentratio ns increased with SCN treatment. Magnesium uptake per unit root volume was decreased, but Mg translocation (% of total plant content in aeri al portion) was increased with SCN treatment. Calcium uptake per unit of root volume was increased, but translocation was unchanged by SCN t reatment. The Ca and P concentration of cysts isolated from the soybea n roots was high. This high concentration of Ca in cysts is interestin g based on the greater root Ca concentration and uptake per unit of ro ot volume in SCN infested plants. Since total uptake and root concentr ations of both K and Mg were decreased by SCN treatment, infested soyb eans might require very high levels of K and Mg fertilization. These r esults indicate that K and Mg fertility should be followed closely in SCM-infested soybean fields.