Phytic acid is an available phosphorus source for maize plants in juvenile phase belonging to two populations with different breeding backgrounds.

Abstract

Background: Applying animal effluent/digestate to forage crops can improve the sustainability of intensive livestock husbandry. Organic phosphorus (P) forms, in particular phytic acid (InsP₆) present in animal effluent/digestate, would benefit from an effective uptake and assimilation by crops thus representing an alternative to mineral P fertilization and controlling P losses in water system. A maize (Zea mays L.) traditional Italian population (VA572), bred before the widespread diffusion of crop chemical fertilization, and a modern commercial hybrid (P1547) were used in this study to investigate their ability of growing in soilless medium using phytic acid (Po) vs phosphate P (Pi) as P sources in a 28-day experiment. The hypothesis was that the different agronomical context in which the two varieties were selected could have brought to different abilities in exploiting P sources for plant growth.

Results: Quantitative and qualitative growth parameters, root enzymatic phosphatase activities and root transcriptome by RNA-seq analysis were analyzed in this study. Both maize populations were able to grow using phytic acid as the sole P source but organic P utilization was less efficient than Pi; a significant root-released phytase activity, induced by the presence of InsP₆, was detected in Po treatment. The RNA-seq analysis showed different expression patterns induced by organic P treatment (Po) in the two populations. The upregulation in Po treatment of a Purple Acid Phosphatase (PAP) gene and of genes involved in inositol transport indicate that both phosphate hydrolysis from InsP₆ by root-secreted PAPs and a direct uptake of myo-inositol at various degrees of phosphorylation could be involved in maize phytic acid exploitation. Root system development and the relationship of P sources with other macro and micro nutrient uptake (N, K, metal ions) were also implied in the response to Po treatment.

Conclusions: This study indicates that phytic acid is a bioavailable P source for maize seedling growth. A wider mobilization of genes/pathways was induced by Po treatment in VA572 with respect to P1547 hybrid. The physiological responses to Po treatment were similar in both populations but the patterns of genes involved often differed being specific to each one.