Natural phosphate and plant growth-promoting microorganisms mitigate water deficit stress in landrace maize

Abstract

The present study aimed to evaluate the biochemical responses of creole maize plants subjected to water deficit (wd), fertilized with reactive natural phosphate (rnp), and inoculated with plant growth-promoting microorganisms (pgpm). The experiment was conducted in pots in a completely randomized design, arranged in a 2 × 7 factorial scheme, with five replicates per treatment. The first factor corresponded to water conditions: 100% of pot capacity (pc), characterizing absence of water deficit, and 50% of pc, characterizing water deficit (wd). The second factor consisted of seven treatments: control (without inoculation and without RNP), RNP alone, Azospirillum brasilense (Az), Bacillus subtilis + Bacillus megaterium (BsBm), efficient microorganisms (em), rnp + Az, and rnp + BsBm. The microorganisms were applied to the seeds before sowing and directly to the soil and plants on a weekly basis until 35 days after sowing (das). At 35 DAS, at the V6 stage, protein contents, guaiacol peroxidase (gpod) enzyme activity, proline, and malondialdehyde (mda) were determined in leaves and roots. The average protein contents in the roots of plants subjected to wd were 66% higher than those of plants not subjected to wd. wd increased gpod activity but reduced proline and mda contents in the roots. The highest proline accumulation was observed in plants that received rnp+BsBm; however, under wd, the BsBm treatment induced greater proline accumulation in the leaves (3.7-fold). mda levels (a product of lipid peroxidation) were higher in the leaves of control, Az, BsBm, or rnp+BsBm plants without wd. The bioinputs were able to mitigate the biochemical alterations caused by wd in creole maize plants.