Topsoil foraging and phosphorus acquisition efficiency in maize (Zea mays)

Abstract

In soybean and common bean, enhanced topsoil foraging permitted by shallow root architectures is advantageous for phosphorus acquisition from stratified soils. The importance of this phenomenon in graminaceous crops, which have different root architecture and morphology from legumes, is unclear. In this study we evaluated the importance of shallow roots for phosphorus acquisition in maize (Zea mays L.). In a field study, maize genotypes with shallower roots had greater growth in low phosphorus soil than deep-rooted genotypes. For physiological analysis, four maize genotypes differing in root shallowness in the field were grown in solid media with stratified phosphorus availability in a controlled environment. Of the four genotypes, one shallow and one deep genotype were also inoculated with arbuscular mycorrhiza (AM). Shallower genotypes had significantly greater growth and phosphorus accumulation compared with deeper genotypes at low phosphorus availability. Mycorrhizal colonisation altered root shallowness under low phosphorus conditions, increasing shallowness substantially in a deep-rooted genotype but slightly decreasing shallowness in a shallow-rooted genotype. Mycorrhizal colonisation increased phosphorus acquisition under low phosphorus availability. Respiration costs of roots and shoots of phosphorusefficient genotypes were significantly lower under low phosphorus conditions compared with inefficient genotypes. The physiological efficiency of phosphorus acquisition, expressed as root respiration per unit of phosphorus acquisition, was greater in shallow rooted genotypes. Our results demonstrate that genetic variation for root shallowness exists in maize, that phosphorus and AM can modulate root shallowness independently, and that a shallower root system is beneficial for plant performance in maize at low phosphorus availability. We propose that root architectural traits that enhance topsoil foraging are important traits for improved phosphorus acquisition efficiency of annual grain crops such as maize in addition to legumes.

Root Phenes for Enhanced Soil Exploration and Phosphorus Acquisition: Tools for Future Crops

“…Cosegregation of QTL controlling a phene with phosphorus acquisition is strong evidence that the phene is important for phosphorus acquisition in a range of phenotypes. Analysis of maize and bean RILs varying in RGA shows that this phene has a dominant influence on phosphorus acquisition, accounting for up to 6-fold variation in phosphorus acquisition and 3-fold variation in yield of bean in low-phosphorus soil (Lynch and Brown, 2001), and 2-fold variation in phosphorus acquisition in maize (Zhu et al, 2005b). QTL associated with RGA in bean cosegregate with yield under phosphorus stress .…”

Plasticity of the Arabidopsis Root System under Nutrient Deficiencies

“…When grown under limited phosphorus (P) availability, roots exhibit a shallower architecture that results from the inhibition of PR elongation and the concomitant increase in LR formation (Williamson et al, 2001;López-Bucio et al, 2002;Sanchez-Calderon et al, 2005). Such an architectural rearrangement of the root is thought to improve the plant's ability to forage P from the usually P-enriched topsoil horizon (Lynch and Brown, 2001;Rubio et al, 2003;Zhu et al, 2005). In contrast to low P, reduced nitrogen (N) availability stimulates PR and particularly LR elongation but not LR initiation (Linkohr et al, 2002;López-Bucio et al, 2003).…”

Three-Dimensional Root Phenotyping with a Novel Imaging and Software Platform

“…Previous studies have shown that external factors can affect root morphology and architecture and that root systems have an innate ability to respond and adapt to their rooting environment (Malamy, 2005). Additionally, many reports indicate that certain root qualities in crop plants can help enhance productivity in resource-limited environments due to improved nutrient and water scavenging abilities (Liao et al, 2001;Zhu et al, 2005;Ribaut et al, 2009). Identifying, evaluating, and selectively introducing both intrinsic and environmentally responsive root architectural characteristics into breeding programs may be a promising area for improving crop production on resource-limited agricultural systems (de Dorlodot et al, 2007).…”