Environmental Effects on Associations among Nitrogen Use Efficiency Traits in Wheat

Nitrogen use efficiency parameters of twelve bread wheat cultivars were studied in nine environments comprised of three nitrogen applications tested over three years. An environment-by-trait association biplot and a trait-association by environment biplot were applied to understand environmental effects on these traits and relationships among them. The following trait associations were relatively stable across environments: negative associations of straw nitrogen content vs. nitrogen remobilization efficiency, straw nitrogen content vs. nitrogen harvest index and a positive association of nitrogen remobilization efficiency vs. nitrogen harvest index. The selection of genotypes with a high nitrogen harvest index and nitrogen remobilization efficiency could be used in the development of cultivars with desired nitrogen use efficiency. A low straw nitrogen content can also be used as a reliable and cost-effective indicator in the selection of genotypes with high nitrogen use efficiency.