Isolation of endophytic fungi from the roots of maize in the saline-alkaline land in Huanghua and screening of strains improving salt tolerance and growth of maize

Abstract:

[Background] Soil salinity is one of the main factors affecting maize yield, and endophytic fungi can significantly improve the resistance and growth of plants. Studying the endophytic fungi of maize is of great significance to increase maize yield. [Objective] To study the growth-promoting effects of endophytic fungi isolated from the roots of maize growing in the saline-alkaline land in Huanghua and the growth-promoting effects of the fungi on maize plants, so as to provide a theoretical basis and material support for increasing the maize yield in saline-alkaline land. [Methods] The tissue culture method was used to isolate endophytic fungi from the roots of maize. The seed soaking experiments were carried out to screen out the strains capable of promoting the germination of maize seeds under NaCl stress. The strains screened out were identified by morphological observation and molecular biological methods and characterized for the growth-promoting properties such as phosphorus- and potassium-solubilizing, indole-3-acetic acid (IAA)-secreting, and siderophore-producing abilities. Pot experiments were conducted to evaluate the effects of the strains on the biomass, plant height, root length, SPAD value, superoxide oxidase (SOD) activity, peroxidase (POD) activity, and malondialdehyde (MDA) content of maize plants under NaCl stress. [Results] A total of 25 strains of endophytic fungi were isolated from the roots of maize, among which the strains DYM7 and DYM11 significantly promoted the germination of maize seeds exposed to 0.15 mol/L NaCl, with the germination rate reaching 90%. DYM7 was identified as Setophoma terrestris and DYM11 as Exserohilum rostratum, both of which had the abilities of solubilizing potassium, producing siderophores, and secreting IAA. Under NaCl stress, strains DYM7 and DYM11 increased the plant height, root length, and SOD and POD activities and reduced the MDA content of maize. Moreover, strain DYM11 increased the aboveground dry weight and underground dry weight of maize plants by 16.43% and 22.17%, respectively, compared with the control. [Conclusion] The endophytic fungal strains capable of improving the salt tolerance and growth of maize by increasing the antioxidant enzyme activities, root length, and plant height, and decreasing the MDA content were screened out in this study. This study provides a theoretical basis and material support for the application of beneficial microbial in coastal saline-alkaline areas in improving the salt tolerance and yields of crops.