Abstract: Oxytropis glabra is a poisonous plant widely distributed in grassland and desert area of Inner Mongolia, its main toxic compound is an alkaloid (swainsonine, SW). Livestock is poisoned or even dead after feeding, resulting in a major loss of grassland animal husbandry in serious cases. This research explored the relationship between SW from Oxytropis glabra in diffe-rent populations and endophytic fungi in Inner Mongolia. One hundred and twenty plants of Oxytropis glabra from 8 populations in Inner Mongolia were collected, and the SW from indivi-dual plant and mycelia were isolated and purified by extraction, centrifugation and ion exchange chromatography. The SW levels were determined by GC-MS. The endophytic fungi were isolated from stems and leaves, and the total DNA of plants and fungi was extracted. The fungal specific sequences were amplified, and the fungus was identified both by microbiological characteristics and DNA sequence comparison. Results showed that SW was detected in 111 plants from 8 popula-tions of Oxytropis glabra with the highest level 369.05 μg·g^-1 and the average level 32.78 μg·g^-1. Endophytic fungi were isolated from 38 planets. Under pure culture condition, mycelia showed loose white villous, and the colonies were round, upheaval with neat edge and radial growth. The color of colonies gradually showed gray, dark gray or brown to dark brown. SW was detected in all endophytic fungi samples with the level range of 0.83-2 573.24 μg·g^-1. The endophytic fungus was identified as Alternaria by microbiological study and 5.8S rDNA/ITS sequence comparison. The plants with Alternaria endophytic fungi contained SW, while the plants without Alternaria endophytic fungi did not contain SW. The cultured Alternaria endophytic fungi synthesized SW.

Key words: Oxytropis glabra, populations, swainsonine, endophytic fungi