Calcium Nutrition of Peanut Grown in Solution Culture. I. Genetic Variation in Ca Requirements for Vegetative Growth

ABSTRACT

Calcium (Ca) deficiency is an important problem in peanut (Arachis hypogaea L.) production, with lines from the sub-species A. hypogaea hypogaea (Virginia type) being considered more susceptible to Ca deficiency than those of A. hypogaea fastigata (Spanish and Valencia types). Fifteen peanut lines comprising five Virginia bunch, one Virginia runner, six Spanish, two Valencia types, and one Valencia × Spanish cross were grown for 30 d in continuously flowing solution culture at constant external Ca concentrations ranging from 9 to 2500 μM. Two lines required <9 μM Ca for near-maximum growth, whereas 5 lines required 15–20 μM, six lines required 25–50 μM, and two lines required >75 μM Ca for maximum growth. The Ca concentration in the youngest fully expanded leaves required for maximum growth also differed considerably among the lines, ranging from <5.7 g kg^?1 in ‘SH-2’ to 17.3 g kg^?1 in ‘Red Spanish’). The differences in solution and tissue Ca requirement for growth did not coincide with the broad botanical groupings despite that Virginia type peanut lines had consistently lower Ca concentrations in youngest fully expanded leaves than Spanish or Valencia lines at all solution Ca concentrations. Leaf magnesium (Mg), potassium (K), phosphorus (P), iron (Fe), and manganese (Mn) concentrations in the leaves decreased as the solution Ca concentration increased and it seemed probable that growth reductions observed at above-optimum Ca concentrations were due to induced deficiencies of P, Mg, or possibly Fe.