Genotypic Response to Multiple Abiotic Stresses: Functional Relationships Among Nutrients

Abstract

Macro- and micro-nutrients estimated in leaves, stems and seed of eleven genotypes of five physiologically diverse crop species (chickpeas, corn, safflower, soybean, and wheat, respectively producing protein, carbohydrates, oil, protein-oil, and carbohydrates-protein, as main seed storage macromolecules) were used in assessing species and genotypic responses to multiple, long-term abiotic stresses. Crops were subjected to two phases, three years each, of multiple abiotic stresses by manipulating length of the growing season and population density under typical management practices of each crop in the upper Midwest, USA. In Phase II, crops were rotated to release the additional edaphic stress of no-rotation in Phase I. Nutrient densities were estimated using LECO analyzer (Carbon and Nitrogen) or ICP instrument (Calcium, Copper, Iron, Manganese, Magnesium, Phosphorus, Potassium, Sulfur and Zinc). Comparisons of functional relationships among nutrients were based on statistics (α, β, and R2) derived from 1000-permutations using reduced major axis (RMA) regression analyses. Genotypic differences in nutrients functional relationships were modulated, in decreasing order, by Carbon:Nitrogen ratio, stress treatments, and storage macromolecules. Comparisons between the β statistics for each nutrient in Phases I and II suggested that differences in nutrient functional relationships between crop species were significantly larger than differences between genotypes within species. Nitrogen, rather than Carbon content, followed by plant density, but not short growing season, influenced some (Phosphorus, Potassium, Sulfur, and Zinc) nutrient relationships and their allocations to leaves, stems and seed of crop species. Functional relationships between Copper, Iron, Sulfur and Zinc, at the seed storage macromolecules level in Phase I and II indicated that oil and protein producing crop species are more prone to larger adverse effects of abiotic stresses than those producing carbohydrates alone or in combination with protein. A thorough understanding of these relationships is critical for screening genetic diversity and designing nutritionally-balanced crop genotypes under abiotic stress.