Chasing drought stress in lpa1-1 maize mutant: Evaluation of the root system architecture and photosynthetic parameters

Phytic acid (PA) represents the major storage form of phosphate (P) in the seeds. It is accumulated as phytate salts with different cations, reducing their bioavailability. Only ruminants can degrade PA due to the presence of phytases in the digestive tract, while monogastrics assimilate only 10% of phytate in feed and 90% is excreted, contributing to P pollution and water eutrophication. Hence, many low phytic acid (lpa) mutants have been isolated: in maize, lpa1-1 is characterized by a 66% reduction in PA, followed by a proportional increase in inorganic P. Unfortunately, PA decrease is followed by negative pleiotropic effects on the seed and on plant performance. One of these agronomic defects observed on lpa1-1 is a greater susceptibility to drought stress, which could be caused by an alteration in the Root System Architecture (RSA). With the aim to assess the effect of drought stress on the mutant, we have compared the RSA of lpa1-1 to a wild phenotype in a two-replicates greenhouse experiment. In this work we present the results obtained. They clearly show that a variety of morphological changes have occurred in the aerial part of the mutant plant rather than in the root system. Drought stress in the mutant seems to be caused by a different photosynthetic efficiency and not by a shallower root system. Studying and overcoming the pleiotropic effects affecting lpa mutants would determine numerous potential benefits for the nutritional quality of food and feed and for the environmental P sustainability in agriculture.