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Soil bioavailability of phosphorus (P) is a major concern for crop productivity worldwide. As phosphatic fertilizers are a non-renewable resource associated with economic and environmental issues so, the sustainable option is to develop P use efficient crop varieties. We phenotyped 82 diverse wheat (Triticum aestivum L.) accessions in soil and hydroponics at low and sufficient P. To identify the genic regions for P efficiency traits, the accessions were genotyped using the 35 K-SNP array and genome-wide association study (GWAS) was performed. The high-quality SNPs across the genomes were evenly distributed with polymorphic information content values varying between 0.090 and 0.375. Structure analysis revealed three subpopulations (C1, C2, C3) and the phenotypic responses of these subpopulations were assessed for P efficiency traits. The C2 subpopulation showed the highest genetic variance and heritability values for numerous agronomically important traits as well as strong correlation under both P levels in soil and hydroponics. GWAS revealed 78 marker-trait associations (MTAs) but only 35 MTAs passed Bonferroni Correction. A total of 297 candidate genes were identified for these MTAs and their annotation suggested their involvement in several biological process. Out of 35, nine (9) MTAs were controlling polygenic trait (two controlling four traits, one controlling three traits and six controlling two traits). These multi-trait MTAs (each controlling two or more than two correlated traits) could be utilized for improving bread wheat to tolerate low P stress through marker-assisted selection (MAS).

Low phosphorus (P) availability induces changes in root architectural traits thereby enabling the root to enhance P acquisition. We investigated the response of 89 diverse wheat genotypes to low (5 µM) and sufficient (500 µM) P in terms of root traits at seedling stage. Results revealed a large genetic variation in root traits under low P. Significant enhancement in total root length (TRL), surface area (TSA), volume (TRV), total root tips (TRT), total root forks (TRF) and crossings (TRC), root dry weight (RDW) and root-to-shoot ratio (RSR) were observed at low P as compared to sufficient P. Low P resulted in significant reduction in total P uptake and average root diameter. Analysis of genotype and genotype × trait showed that the principal components (PC) 1 and 2 governed 69.2 and 70.7% variability at sufficient P and low P, respectively. Among traits, average root diameter contributed 38.7% variability at sufficient P and 49.5% at low P. Under low P, significant correlations were observed between TRL and TSA (r = 0.94), TSA and TRV (r = 0.91), TRL and TRC (r = 0.90). The higher percentage distribution for root traits (TRL, RSA, RV and RT) was recorded in 0–0.5 mm diameter class under both P concentrations. Clustering of genotypes based on relative values revealed that in cluster III and IV, all root traits were enhanced in comparison to cluster I and II. Good performers in cluster III included BABAX, CARAZINHO, HD 2891, MARINGA and SUNCO. Genotypes grouped under cluster IV included BT-SCHOMBURGK, BWL 5200, KYPO 328 and OLYMPIC. Results of the current study could be used to develop P efficient genotypes with reduced dependency on P fertilizers.

Phosphorus (P) is one of the limiting factors for plant growth and productivity due to its slow diffusion and immobilization in the soil which necessitates application of phosphatic fertilizers to meet the crop demand and obtain maximum yields. However, plants have evolved mechanisms to adapt to low P stress conditions either by increasing acquisition (alteration of belowground processes) or by internal inorganic P (Pi) utilization (cellular Pi homeostasis) or both. In this review, we have discussed the adaptive strategies that conserve the use of P and maintain cellular Pi homeostasis in the cytoplasm. These strategies involve modification in membrane lipid composition, flavanol/anthocyanin level, scavenging and reutilization of Pi adsorbed in cell wall pectin, remobilization of Pi during senescence by enzymes like RNases and purple acid phosphatases, alternative mitochondrial electron transport, and glycolytic pathways. The remobilization of Pi from senescing tissues and its internal redistribution to various cellular organelles is mediated by various Pi transporters. Although much efforts have been made to enhance P acquisition efficiency, an understanding of the physiological mechanisms conserving internal Pi and their manipulation would be useful for plants that can utilize P more efficiently to produce optimum growth per unit P uptake.