Efficient Mineral Nutrition: Genetic Improvement of Phosphate Uptake and Use Efficiency in Crops

Abstract

Phosphorus (P) is an essential macronutrient for plants, the lack of which can be a major constraint for agricultural productivity. Economic, political and environmental factors have prioritized the need for research on P acquisition efficiency (PAE), P utilization efficiency (PUE) and P fertiliser uptake efficiency in crops. P has critical functions in plants and complex interactions in soils. Appropriate screening approaches and implications of improvement in crop production are discussed. P acquisition is mediated by members of phosphate transporter families and the roles of these phosphate transporters as well as enzymes involved in P partitioning and re-translocation are complex. There is also a critical importance of regulatory genes including transcription factors, signalling pathways and apparently other P-responsive genes with unknown function. Furthermore, morphological and biochemical responses enhance P solubility in the soil and facilitate uptake and include root plasticity, secretion processes and symbioses. Exploitation of genetic variation, classical breeding and biotechnological gene modification of target genes are future routes for crop improvement. There is a need for selection not just for uptake but also focussing on P storage pools within cells and tissues, and additionally a consideration of crop P requirements during the different growth stages of crops. The review concludes with a summary giving an outlook to future questions related to crop PAE/PUE improvement.