Physiology and Inheritance of Efficiency in Potassium Utilization in Tomatoes Grown under Potassium Stress1

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Abstract
Genetic control of efficiency in K utilization was investigated by screening 156 lines of tomato (Lycopersicon esculentum Mill.) in nutrient culture solution (one plant per container) at a stress level of K (5 mg per plant). Efficiency in K utilization was defined and expressed as the mg of dry weight produced per mg of K absorbed by a plant (KER). Under K stress, an efficient line produced an average of 79% more dry wt than an inefficient line. Yields of the lines were comparable under adequate K (200 mg per plant). The efficient lines contained 39% less K and 29% more Na in their tissues when grown at the low levels of K. Differences in K uptake or translocation of K from roots to shoots could not explain variations in efficiency of K utilization. Partial substitution of K by Na was important in high K efficiency. However, part of the efficiency was associated with K functions for which Na could not substitute. One line responded favorably to Na even at moderate levels of K. Additive gene effects made the major contribution to variation in efficiency of K utilization. Dominance and epistatic gene effects were important only in 1 of the 4 inefficient × efficient families and in families derived from parents of similar efficiency. No evidence for maternal control of efficiency in K utilization was observed.

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