Abstract
Food insecurity is a looming threat for the burgeoning world population. Phosphorus (P), which is absorbed from soil as inorganic phosphate (Pi), is an essential macronutrient for the growth of all agricultural crops. This study reports phenotype analysis for P responses in natural field and greenhouse conditions, using 54 genotypes of foxtail millet (Setaria italica) representing wide geographic origins. The genotype responses were assessed in natural field conditions in two different seasons (monsoon and summer) under Pi-fertilized (P+) and unfertilized (P-) soil for eight above-ground traits. Enormous variations were seen among the genotypes in phenotypic responses for all the measured parameters under low P stress conditions. Variations were significant for plant height, leaf number and length, tillering ability and seed yield traits. Genotypes ISe 1234 and ISe 1541 were P+ responders, and the genotypes ISe 1181, ISe 1655, ISe 783 and ISe 1892 showed tolerance to low P for total seed yield. Genotypes that performed well under P- conditions were almost as productive as genotypes that performed well under P+ conditions suggesting some genotypes are well adapted to nutrient-poor soils. In the greenhouse, most of the genotypes produced changes in root architecture that are characteristic of P- stress, but to differing degrees. Significant variation was seen in root hair density and root hair number and in fresh and dry weight of shoot and root under P- stress. However, there was not much difference in the shoot and root total P and Pi levels of five selected high and low responding genotypes. We noticed contrasting responses in the greenhouse and natural field experiments for most of these genotypes. The leads from the study form the basis for breeding and improvement of foxtail millet for better Pi-use efficiency.
Highlights
As a component of biomolecules such as nucleotides, phospholipids and phosphorylated intermediates of several processes including photosynthesis and respiration, phosphorus (P) plays several important functions in living systems
Plants take up P from the soil in the form of inorganic phosphate (Pi) and the process is affected by several external factors such as soil pH, microbial activity, cationic abundance and the presence of mycorrhizal fungi [1]
We examined the phenotypic responses of 54 foxtail millet genotypes (Setaria italica) to phosphate under phosphate fertilized and unfertilized conditions
Summary
As a component of biomolecules such as nucleotides, phospholipids and phosphorylated intermediates of several processes including photosynthesis and respiration, phosphorus (P) plays several important functions in living systems. P is an irreplaceable, essential element for crop production. Plants take up P from the soil in the form of inorganic phosphate (Pi) and the process is affected by several external factors such as soil pH, microbial activity, cationic abundance and the presence of mycorrhizal fungi [1]. Even where soils are rich, P uptake remains a limiting factor for plant growth, due to chemical fixation in organic or inorganic form. Limiting Pi in soil leads to poor soil health and can be a major impediment for crop growth. Pi-deficiency significantly hampers crop production, affecting 5.7 billion hectares of land worldwide [2]. To sustain crop production in continuous cropping systems, replacement of depleted nutrients is carried out through the external application of fertilizers. The sustainable use of phosphate is an important requirement
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