Shoot and root responses to low phosphorus and their genotypic variability in selected cultivars of Japanese core collections of maize and soybean

Abstract

ABSTRACT Low phosphorus (P) stress in agricultural soils is a global problem in crop production. A greater understanding of the genotype-specific responses under low P stress is imperative for producing P-efficient genotypes. This study first evaluated Japanese core collections of maize (86 landraces) and soybean (94 landraces) to low P under hydroponic conditions. Ten cultivars of each species were further evaluated in a pot experiment with two P supply rates: low P (10 mg P kg−1) and high P (50 mg P kg−1). Root morphology, acid phosphatase (ACP) activity, and rhizosphere soil pH were characterized 30 days after planting. A sufficient genotypic variation was found in both species under both P conditions. A significant decrease in biomass, except in maize cultivar JMC 76 and soybean cultivar GmJMC033, and increased phosphorus use efficiency (PUE) under low P conditions were observed. The maize cultivars: JMC 76, JMC 57, JMC 58, and JMC 8 and soybean cultivars: GmJMC033, GmJMC040, and GmJMC085 showed distinctive root modifications characterized by the high root-to-shoot ratio (RRS), total root length (TRL) and specific root length (SRL) under low P stress indicating their low P tolerance. Maize had more significant ACP activity compared to soybean under low P stress. The maize cultivars, which showed low P tolerance, were highly dependent on root morphological traits rather than physiological traits (ACP activity, rhizosphere acidification, and PUE), whereas soybean cultivars were dependent on both traits. In conclusion, the plasticity of the root system is crucial in both maize and soybean to tolerate P deficiency. These genotype-specific adaptations could be combined with agronomic strategies to enhance the overall P-use efficiency in cropping systems.