The Mexican giant maize of Jala landrace harbour plant-growth-promoting rhizospheric and endophytic bacteria

Abstract

The giant landrace of maize Jala is a native crop cultured in Nayarit and Jalisco States in the occident of México. In this study, after screening 374 rhizospheric and endophytic bacteria isolated from rhizospheric soil, root, and seed tissues of maize Jala, a total of 16 bacterial strains were selected for their plant-growth-promoting potential and identified by 16S rRNA phylogenetic analysis. The isolates exhibited different combinations of phenotypic traits, including solubilisation of phosphate from hydroxyapatite, production of a broad spectrum of siderophores such as cobalt, iron, molybdenum, vanadium, or zinc (Co²⁺, Fe³⁺, Mo^{2 +}, V⁵⁺, Zn²⁺), and nitrogen fixation capabilities, which were detected in both rhizospheric and endophytic strains. Additional traits such as production of 1-aminocyclopropane-1-carboxylate deaminase and a high-rate production of Indoleacetic Acid were exclusively detected on endophytic isolates. Among the selected strains, the rhizospheric Burkholderia sp., and Klebsiella variicola, and the endophytic Pseudomonas protegens significantly improved the growth of maize plants in greenhouse assays and controlled the infection against Fusarium sp. 50 on fresh maize cobs. These results present the first deep approach on handling autochthonous microorganisms from native maize with a potential biotechnological application in sustainable agriculture as biofertilizers or biopesticides.

Keywords: Indoleacetic acid; Maize; Nitrogen fixation; Phosphate solubilisation; Plant-growth-promoting bacteria (PGPB); Siderophore.

Fig. 1

Phosphate-solubilizing activity of bacteria isolated from Jala maize landrace. Production of clear halo zones of solubilization on NBRIP agar plates by Pantoea sp. E2K4. Weak halos formed by Pseudomonas protegens E1BL2 and Phytobacter diazotrophicus Z2WL1 strains, and no halo was observed with Rhizobium pusense E2K3, which was used as the negative control

Fig. 2

Detection of siderophore production by colour change on CAS-blue agar supplemented with five different ions (Co²⁺, Fe³⁺, Mo²⁺, V⁵⁺, Zn²⁺) after 48 h of incubation by the strains (clockwise sense) (1) Klebsiella variicola R3J3HD7, (2) Achromobacter xylosoxidans Z3AD5a, (3) Pseudomonas japonica Z2K3, (4) Achromobacter xylosoxidans Z2K8, (5) Pseudomonas protegens E2HL9, (6) Pseudomonas protegens E1BL2, (7) Pantoea sp. Z2WD2 and (8) Chryseobacterium gleum Z1HL3

Fig. 3

Growth kinetics of the utilization of ACC as a sole nitrogen source by bacteria isolated from Jala maize landrace. Panels A1 to 4 LGI medium supplemented with ACC as the sole source of nitrogen. Panels B1 to 4 show bacteria growing on LGI medium without any source of nitrogen (nitrogen fixation control)

Fig. 4

Growth promotion assay on maize plants from the landrace “Conejo” inoculated individually with either endophytic or rhizospheric PGPB isolated from Jala maize. A Maize plants of 50 days inoculated with PGPB under the following scheme (from left to right): non-inoculated plant, K. variicola R3J3HD7, P. protegens E2HL9, P. protegens E1BL2, Burkholderia sp. R3J3HD10, and H. seropedicae E2WL3. B Dry weight of the maize plants on 50th day. C Stem and root length of treated plants after 50 days. Data analysis was performed using GraphPad PRISM statistics program. Differences between treatments and control means were determined using two-way ANOVA with multiple comparison (*p < 0.05)

Fig. 5

Antagonistic interaction of Fusarium sp. 50 with the bacterial isolates Burkholderia sp. R3J3HD10, K. variicola R3J3HD7, and two strains of P. protegens E1BL2 and E2HL9. A Growth of Fusarium sp. 50 in potato dextrose agar (PDA). B Inhibition of fungal growth by P. protegens E1BL2 and E2HL9. C Inhibition of fungal growth by Burkholderia sp. R3J3HD10 and K. variicola R3J3HD7. D Maize cob protection assay on “Conejo” maize cobs inoculated with PGPB, after 7 days of infection with Fusarium sp. 50. Toothpicks mark the inoculation point of Fusarium sp. 50