A soil-based method to screen for zinc efficiency in seedlings and its ability to predict yield responses to zinc deficiency in mature plants

Nutrient efficiency measures the ability of a plant to grow and produce grain when the availability of a nutrient is low. Seedling tests for nutrient efficiency will be most useful if the results correlate well with grain yield responses. In two experiments, a diverse range of barley genotypes was screened for zinc (Zn) efficiency at the seedling stage and the relationship between vegetative and grain measures of Zn efficiency was examined. In Expt 1, 54 barley and 4 wheat genotypes were grown at 2 levels of Zn (0.02 and 0.8 mg/kg soil) for 21 days. Zinc efficiency ranged from 18% to 52%. The visual symptoms of Zn deficiency varied considerably between genotypes and was significantly correlated with Zn efficiency. Root:shoot ratio was increased by Zn deficiency and varied between genotypes, but these differences were not related to Zn efficiency. Zinc concentration and especially Zn content at 0.02 mg Zn/kg were significantly related to Zn efficiency. In Expt 2, 15 genotypes, selected on the basis of their response in Expt 1, were grown to maturity at either 0.1 mg Zn/kg or 2.4 mg Zn/kg. Zn efficiency, based on relative grain yield, ranged from 5% to 54%. High efficiency was associated with a large number of grains per plant and high kernel weight. Rankings of Zn efficiency in the experiment were significantly correlated with the rankings for visual scores in Expt 1. The 2 experiments suggested that deficiency symptoms at the seedling stage can identify efficient genotypes and could be useful for routine screening for Zn efficiency. Independent data from multisite comparisons over 8 years were used to examine the long-term performance of efficient and inefficient genotypes in the field. Hierarchical cluster was used to define efficient and inefficient groupings within the 56 genotypes examined in Expt 1, based on their responses to Zn. The Zn-efficient genotypes tended to yield more than the Zn-inefficient genotypes. The data provide prima facae evidence that high Zn efficiency may contribute to improved adaptation of barley in South Australia