Acquisition Efficiency by Maize Landraces in Acid Soils of Mexico

摘要

Amain constraint to agricultural productivity in the central Mexican highlands is low available soil phosphorus (P) exacerbated by high P sorption capacity of the Andisols. Therefore, substantial amounts of P fertilizers must be applied to obtain optimum crop yields. One cost-effective strategy for this type of soil is to enhance the plant's efficiency to acquire inorganic phosphorus (Pj) from soil and/or to use P more efficiently. The present study was conducted to evaluate genotypic variation in both root architecture and plant growth traits associated with P acquisition efficiency (PAE) and/or P utilization efficiency (PUE) of maize landraces in a P-deficient soil. The results showed that genotypes differed greatly in plant growth, grain yield, root morphology, P uptake, PAE, PUE, and P efficiency defined as growth with sub-optimal P availability. Phosphorus-efficient genotypes not only had greater biomass per unit of absorbed P, but also developed larger root systems, produced more nodal and lateral roots, and had greater root hair density and P uptake per unit root weight than did the P-inefficient genotypes under P deficiency. Genotypes with enhanced nodal rooting and dense root hairs had greater P uptake and growth under low P. The 32P isotope dilution technique was employed to assess the ability of the genotypes tested to utilize P from different P sources. The P-responsive genotypes showed increased P acquisition from fertilizer, whereas P-efficient genotypes accessed soil P not available to P-inefficient ones. These results indicate that maize landraces exhibit variation for several root traits that may be useful for genetic improvement of P acquisition efficiency in maize.