Salt stress inhibited the growth of maize. B46 and NC236 were chosen as materials and NaCl concentrations (0, 55, 110, 165, and 220 mmol L⁻¹) were set. We found the activities of SOD, POD, CAT, APX, GR, MDHAR, and DHAR decreased under NaCl stress. Compared with NC236, the contents of AsA and GSH, AsA/DHA and GSH/GSSG of B46 decreased. The content of O₂⁻, H₂O₂, MDA, and EL of B46 increased. The contents of NO₃⁻ and NO₂⁻ decreased, while the content of NH₄⁺ increased under high NaCl concentration. The activities of NR and NiR decreased, while the activities of GS and GOGAT increased first and then decreased. For B46 and NC236, the maximum of NADH-GDH and NAD-GDH appeared at 165 and 110 mmol L⁻¹ NaCl concentration, respectively. Compared with B46, and the GOT and GPT activities of NC236 increased first and then decreased. With the increase of NaCl concentration, the contents of proline, soluble protein, and soluble sugar were increased. The Na⁺ content of B46 and NC236 increased, and the K⁺ content and K⁺/Na⁺ decreased. Compared with NC236, B46 had higher IAA content in leaf, higher Z + ZR content in leaf and root, and lower ABA content in leaf and root.

Soil salinization is currently one of the main abiotic stresses that restrict plant growth. Plant endophytic bacteria can alleviate abiotic stress. The aim of the current study was to isolate, characterize, and assess the plant growth-promoting and saline and alkaline stress-alleviating traits of Peribacillus simplex M1 (P. simplex M1) isolates from maize. One endophytic bacterial isolate, named P. simplex M1, was selected from the roots of maize grown in saline–alkali soil. The P. simplex M1 genome sequence analysis of the bacteria with a length of 5.8 Mbp includes about 700 genes that promote growth and 16 antioxidant activity genes that alleviate saline and alkaline stress. P. simplex M1 can grow below 400 mM NaHCO₃ on the LB culture medium; The isolate displayed multiple plant growth-stimulating features, such as nitrogen fixation, produced indole-3-acetic acid (IAA), and siderophore production. This isolate had a positive effect on the resistance to salt of maize in addition to the growth. P. simplex M1 significantly promoted seed germination by enhancing seed vigor in maize whether under normal growth or NaHCO₃ stress conditions. The seeds with NaHCO₃ treatment exhibited higher reactive oxygen species (ROS) levels than the maize in P. simplex M1 inoculant on maize. P. simplex M1 can colonize the roots of maize. The P. simplex M1 inoculant plant increased chlorophyll in leaves, stimulated root and leaf growth, increased the number of lateral roots and root dry weight, increased the length and width of the blades, and dry weight of the blades. The application of inoculants can significantly reduce the content of malondialdehyde (MDA) and increase the activity of plant antioxidant enzymes (Catalase (CAT), Superoxide Dismutase (SOD), and Peroxidase (POD)), which may thereby improve maize resistance to saline and alkaline stress. Conclusion: P. simplex M1 isolate belongs to plant growth-promoting bacteria by having high nitrogen concentration, indoleacetic acid (IAA), and siderophore, and reducing the content of ROS through the antioxidant system to alleviate salt alkali stress. This study presents the potential application of P. simplex M1 as a biological inoculant to promote plant growth and mitigate the saline and alkaline effects of maize and other crops.

Maize (Zea mays L.) stalk rot, caused primarily by the soilborne fungal pathogen Fusarium spp., reduces maize quality and yield worldwide. This study was undertaken to develop and utilize a rapid continuous injection inoculation technique to evaluate maize inbred lines for resistance to Fusarium spp. under field conditions, which could facilitate the identification and development of new sources of host resistance to manage the disease. Continuous injection inoculation is a rapid, stable, and simple method that can evaluate the resistance of maize inbred lines to Fusarium stalk rot (FSR) within 20 days. To verify the feasibility and reliability of the inoculation method, Fusarium graminearum, F. proliferatum, and F. subglutinans were isolated, identified, and inoculated into maize at the six-leaf stage (V6) by a veterinary adjustable bottle continuous vaccination syringe. Our results showed that, of a total of 97 inbred maize lines, 6 (6.2%) showed high resistance to maize stalk rot, 20 showed resistance (20.6%), 32 were susceptible (33.0%), and 39 were very susceptible (40.2%). Based on simple sequence repeat markers, an analysis of molecular variance indicated a significant correlation between population of the inbred maize line and resistance to FSR (P = 0.001). Overall, this study provided a systematic, rapid, stable, and simple identification method for maize inbred lines resistant to FSR in the field. At the same time, this method was also suitable for genetic diversity analysis of maize inbred lines resistant to FSR.

Background Soil alkalization inhibits plant growth and yield, the endophytic plant growth-promoting bacteria (PGPB) can alleviate salt stresses for plant. Methods: Isolate a NaHCO₃-tolerant Bacillus amyloliquefaciens strain (ZmBA DSM7), characterize its PGP traits, elucidate the physiological and biochemical mechanisms by which it enhances maize growth. Results: A ZmBA DSM7 strain was isolated from the root of maize growing in a mildly alkaline soil (pH 8.8). The strain exhibited high tolerance to 500 mM NaHCO₃ and maintained its PGP traits, ZmBA DSM7 had a positive effect on maize seed germination and alkaline stress tolerance by enhancing seed vigor under normal or alkaline growth conditions. The maize seedlings inoculation with ZmBA DSM7 markedly improved chlorophyll content and reduced oxidative damage by lowering malondialdehyde (MDA) content and enhancing the antioxidant enzymes activities in the pots. In the field, ZmBA DSM7-inoculated plants showed a increase in yield (such as the ear length, the number of kernels row number, average spike weight, the 100-grain weight, and so on). Conclusion: The ZmBA DSM7 promotes maize growth and mitigates NaHCO₃-induced alkaline stress in maize by a multifaceted mechanism involving enhanced nutrient acquisition (N, P and K) and antioxidant status and improved soil quality.