ARS | Publication request: A role for root morphology and related candidate genes in P acquisition efficiency in maize

Submitted to: Functional Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 28, 2012
Publication Date: June 28, 2012
Citation: Desousa, S., Clark, R.T., Mendes, F., De Oliveira, A., De Vasconcelos, M., Parentoni, S.N., Kochian, L.V., Guimaraes, C.T., Magalhaes, J.V. 2012. A role for root morphology and related candidate genes in P acquisition efficiency in maize. Functional Plant Biology. DOI: org/10.1071/FP12022.

Interpretive Summary: There is a growing understanding about how important root systems are to crop traits such as nutrient and water acquisition. For example, with regards to tolerance to low phosphorous (P) in the soil, it is now known that root system architecture (RSA), or where the plant places different roots in the soil within the entire root system, plays a key role in the ability for the plant to efficiently acquire P from low P environments. In this study we grew a diverse panel of corn lines on low and sufficient P soils in the field to identify P efficient (good yield under low P conditions) and P inefficient lines. Subsequently, these two lines were grown in a paper pouch system that allowed us to supply low or sufficient P nutrient solution and maintain root system architecture, and then a novel root imaging system we was used to digitally image the entire root system, and then quantitatively analyze images to determine root system architecture traits such as total root growth, the total volume the root system explores, and root angle. Statistical analysis of these root traits allowed us to identify root traits that are positively correlated with P efficiency. We also investigated the root expression of a number of genes that are candidates for controlling root growth and architecture and found several of these genes that were expressed much more highly in roots of the P efficient corn line. These findings may help to identify early molecular and physiological markers for P efficiency in corn, and may also provide the basis for identifying molecular determinants of P efficiency for use in crop improvement.

Technical Abstract: Phosphorus (P) is an essential nutrient for plants and is acquired from the rhizosphere solution as inorganic phosphate. P is one of the least available mineral nutrients particularly in highly weathered, tropical soils, substantially limiting plant growth. This work aimed at studying a possible effect of root morphology and the expression pattern of related candidate genes on P efficiency in maize. Our field phenotyping results under low and high P conditions enabled us to identify two contrasting genotypes for P acquisition efficiency that were used for the root traits studies. Root morphology was assessed in a paper pouch system to investigate root traits that could be involved in P acquisition efficiency. The genes, Rtcs, Bk2 and Rth3, that are known to be involved in root morphology, showed higher expression in the P efficient line relative to the P inefficient line. Overall, root traits showed high heritability and a low coefficient of variation. Out of the 24 root traits analyzed, 10 pair-wise comparisons yielded correlation coefficients exceeding 0.9. In conjunction with a principal component analysis we found that only four root traits were needed to adequately represent the diversity among genotypes. The information generated by this study will be useful for establishing early selection strategies for P efficiency in maize, which are needed to support subsequent molecular and physiological studies.