Potassium Level Suitable for Screening High Magnesium Containing Grass Seedlings Under Solution Culture

Abstract

There is a continued need for breeding high-Mg grass cultivars with low grass tetany risk. Since interaction between magnesium (Mg) and potassium (K) exists, there is a possibility that genotypes characterized for higher Mg concentration may exhibit contrasting behavior for nutrient uptake with K application. A solution culture experiment was conducted to find a suitable K level for individual selection of high-Mg plants. Three K treatments of 1.0, 5.0, and 25 mM were superimposed. The uptake pattern of Mg, calcium (Ca), and K for approved high-Mg cultivars of Italian ryegrass (Magnet), orchardgrass (Mgwell), and tall fescue (HiMag) were compared with that of control cultivars. The seedlings were evaluated for shoot dry weight, amount of nutrient uptake, and average shoot nutrient concentrations. There was an increase in shoot dry weight grown with higher nutrient solution K levels. The effect of K on the trend of Mg uptake was paralleled among the high-Mg cultivars of the three species. The high-Mg cultivars showed higher Mg uptake and average shoot Mg concentrations than the control cultivars. Potassium uptake and average shoot K concentrations of high-Mg cultivars was always lower than the control cultivars. The greatest difference between the controls and high-Mg plants for average shoot Mg and K concentrations was observed in the plants grown under 5.0 mM level of K. This indicates the effectiveness of screening high-Mg grass seedlings using 5.0 mM level of K under solution culture condition. Methodology introduced in this experiment is aimed at expediting the term necessary for screening high-Mg plants.

Acknowledgments

The authors thanks to Dr. H. F. Mayland at the Northwest Irrigation and Soils Research Laboratory, Idaho, USDA, for providing the seeds of the high-Mg cultivars of tall fescue and Italian ryegrass used in this study, and also for his valuable suggestions. The authors are also grateful to Susan Byatt, Purdue University, for reading the manuscript critically.