# Study on the colonization changes with different dark septate endophytes and their regulation of the growth and physiological mechanisms of Pinus sylvestris var. mongolica under drought stress

## TL;DR

This study explores how different dark septate endophytes affect the growth and drought tolerance of a pine species.

## Contribution

The study identifies specific endophyte strains that improve drought tolerance in pine seedlings through morphological and physiological changes.

## Key findings

- Inoculation with J09 and A065 improved plant growth and physiological indicators under drought stress.
- DSE colonization morphology changes, such as thicker hyphae and more microsclerotia, correlate with improved drought tolerance.
- J09 and A065 show potential for use in microbial fertilizers in drought-prone areas.

## Abstract

This study aimed to understand the colonization effects of dark septate endophytes (DSE) on Pinus sylvestris var. mongolica under drought stress.

With the pot experiment in the greenhouse, the seedlings of P. sylvestris var. mongolica were inoculated with J09, J32, J35, A065, and the sterile PD medium. Under well-watered (WW) (80% field water capacity), moderate-watered (MW) (60% field water capacity), and low-watered (LW) (LW) conditions (40% field water capacity), the difference in the colonization morphology of DSE, the growth index of seedlings, physiological indexes of seedlings, physical and chemical properties of rhizosphere soil, and enzyme activities of rhizosphere soils were studied.

The effects of different DSE strains on drought tolerance of annual seedlings of P. sylvestris var. mongolica were determined by indoor weighing and water supplement methods. With the strength of drought, the diameter of hyphae became thicker, the septum became shorter, and the number of microsclerotia increased. The change of DSE colonization morphology may be one of the mechanisms to improve the drought tolerance of host plants, and the type of DSE colonization significantly affects the drought tolerance of host plants. Inoculation of J09 and A065 can alleviate the adverse effects of moderate and severe drought stress on host plants by improving plant growth indicators, increasing physiological indicators, enhancing rhizosphere soil physicochemical properties, and maintaining higher rhizosphere soil enzyme activity, respectively. Two-way analysis of variance (ANOVA) results indicated that the interaction between DSE and drought stress significantly affected the growth and physiological indexes of the plants, enzyme activities, and physicochemical properties of rhizosphere soil (P < 0.05).

J09 and A065 have the potential to be applied in the microbial fertilizer for seeding in a drought area.