Abstract
Leguminous locoweeds cause toxicosis to grazing animals in western China and western USA. Swainsonine, a toxic alkaloid, is produced by the endophytic fungus Alternaria section Undifilum sp. living within the locoweed plants. Nothing is known of the other endogenous fungi associated with locoweed and it is unknown if the presence of Alternaria sect. Undifilum sp., a potential mutualist, in a locoweed influences the fungal microbiome associated with the plant. To help address these questions, endogenous fungi associated with three locoweed species (Oxytropis glabra, Sphaerophysa salsula, and Astragalus variabilis) collected from grasslands from western China were evaluated. Fungi were isolated from the tissues and identified by morphological features and sequencing of the internal transcribed spacer (ITS) regions. A total of 1209 fungal isolates were obtained from 1819 tissues for an isolation rate of 66.5%. Alternaria sect. Undifilum oxytropis, Alternaria spp. and Fusarium spp. were most commonly isolated. Plant host species, plant part, and environment influenced the endogenous fungal communities isolated from the locoweed plants. There were significant differences in the diversity of fungal species isolated from O. glabra from two sites, and no differences between the diversity of fungi isolated from A. variabilis from two sites. Alternaria sect. Undifilum was found most frequently associated with toxic locoweeds. Plants or plant parts that did not yield this endophyte had more plant pathogenic fungi associated with them. This is the first report of the diversity of fungi associated with these locoweeds and the first to suggest a beneficial role for Undifilum. Key words: Fungal endophytes, Undifilum sp., locoweeds.
Highlights
One hundred sixty-eight fungal isolates were obtained from 211 tissues from O. glabra from BayanHot with an isolation rate of 79.6%, and 417 fungal isolates were obtained from 642 tissues from O. glabra from Yinchuan with an isolation rate of 65.0%
The diversity of fungi associated with locoweeds, the sampling sites, plant part and isolation rates were considered in this study
Location/environment, plant species, and presence/absence of the fungal endophyte Alternaria sect Undifilum all had strong impacts on the diversity of fungi associated with the locoweed plants
Summary
James et al.,1981; Allred, 1991; Cook et al, 2009b). Locoweeds are primarily species of Astragalus and Oxytropis genera and have been reported from the Americas (western USA and South America) and Asia (Allred, 1991; Robles et al, 2000; Yu et al, 2010). Swainsonine is an indolizidine alkaloid that was first identified from Swainsona, a toxic legume that is found in Australia (Colegate et al, 1979). Losses due to locoism depend on the severity of poisoning, but have been estimated at $300 million annually in the western United States due to poisoned cattle, sheep, and horses (Torell et al, 2000; Turner et al, 2012)
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