Low-Phytate Grains to Enhance Phosphorus Sustainability in Agriculture: Chasing Drought Stress in Lpa1-1 Mutant

Phytic acid (PA) is an anti-nutritional factor for monogastrics and contributes to phosphorus pollution. The low phytic acid (lpa) trait can provide several benefits to the nutritional quality of foods/feeds and to environmental sustainability. In maize, four lpa1 mutants have been isolated, and lpa1-1 is the most promising. Nevertheless, these mutations are frequently accompanied by many negative pleiotropic effects affecting plant performance. One of these is a greater susceptibility to drought stress, probably caused by an alteration in the root system. In this work, we set up an experiment in hydroponics and two in mesocosms, where pots were built using transparent PVC sheets to better access the roots. The results suggested that neither root architecture nor root depth are limiting factors in mutant plants. In hydroponics, the dry weight of the mutant and the root area per unit of length were twice that of B73. However, lpa1-1 exhibited a reduced efficiency of photosystem II (Fv/Fm, 0.810 vs. 0.800) and a reduced leaf temperature (−0.5 °C compared to wild-type), probably due to increased water loss. Furthermore, molecular analysis performed on genes involved in root development (rtcs, rtcl, rum1, and BIGE1) revealed the abundance of rtcs transcripts in the mutant, suggesting an alteration in auxin polar transport.