Endophytic association between Alternaria oxytropis and Oxytropis kansuensis affected by nutritional conditions and temperature

Abstract

Alternaria oxytropis has been reported as an endophyte of species in the genera Astragalus and Oxytropis (Fabaceae) in the USA and China. Infected plants contain the alkaloid swainsonine produced by the fungus, and this causes poisoning of grazing animals. Therefore, ecological investigations are important to clarify the extent of this endophytic association. Seeds of O. kansuensis were collected from a locality known for indigenous A. oxytropis in China and were cultured on artificial media under controlled conditions for about two months. Less than 50% of seeds germinated with colonies of A. oxytropis, however, germination and seedling growth were influenced by the type of culture media used as well as temperature. Seedling growth with colonies of the fungus was significantly better on low nutrient media at low temperature (20 °C) than that on a high nutrient media at high temperature (25 °C). Seedlings with colonies of the fungus on a high nutrient media were eventually killed by the fungus. It is suggested that the endophytic association between the fungus and plants is affected by nutritional conditions and temperature.