Potassium and cyst nematode effect on nutrition of soybean cultivars with resistance to cyst nematode

Abstract

Greenhouse and laboratory research studied K and CI nutrition of four soybean [Glycine max (L) Merril] cultivars with differential resistance to Soybean Cyst Nematode (SCN, Heterodora glycines Ichinohe). The cultivars: Forrest (Group V, resistant to races 1 and 3), Bradley (Group VI, resistant to races 1, 3 and 4), Essex (Group V, susceptible), and Davis (Group VI, susceptible*) were used. Potassium treatments were zero K, K₂SO₄ and KCI, and SCN treatment was zero and 500 eggs/100 g of previously sterilized soil. Single plants were grown for 30‐days in 400 g of soil in 3.5 cm pots maintained at 23°C. Plants were separated into roots and shoots for analysis. Post harvest SCN cyst counts were completed to evaluate cultivar‐K treatment effect on SCN population dynamics and treatment effects on root and shoot K, Ca, Mg and CI.

Cyst counts were a function of cultivar resistance and inoculation, and were not affected by K treatment. Root and shoot weights of all cultivars were lower In the SCN inoculated pots. Potassium treatments did not alter the SCN negative effect on root weight, but KCI appeared to reverse the negative effect that SCN inoculation had on shoot weight of Bradley. SCN Inoculation appeared to reduce CI concentration in the roots of all cultivars, increase root K of Bradley and no effect on root K of Davis, Essex and Forrest. Transiocation of K from roots to shoots was not adversely affected by SCN inoculation. The KCI treatment increased shoot CI concentration of cultivars in order Essex > Davis > Forrest > Bradley. The order of correlation of root CI concentration with shoot CI concentration was: Essex (r = 0.80**) > Bradley (r = 0.70**) > Davis (r = 0.54**) > Forrest (r = 0.40**) suggesting difference in root CI adsorption characteristcs and CI translocation characteristis to the shoots. Additional research is needed to determine to what extent root and shoot CI accumulation characteristics are related to SCN resistance and if the shoot CI accumulation characteristics is independent of root CI adsorption characteristics.