Localization of endophyticUndifilumfungi in locoweed seed and influence of environmental parameters on a locoweed in vitro culture system

Abstract

Endophytic Undifilum oxytropis (Q. Wang, Nagao & Kakish) Pryor, Creamer, Shoemaker, McLain-Romero, & Hambleton found within toxic locoweeds ( Astragalus and Oxytropis spp.) produces the alkaloid swainsonine, which is responsible for locoism in grazing animals. We sought to determine the location of U. oxytropis within locoweed seed, develop endophyte free plants, and assess the influence of environmental stresses on locoweed and endophyte cultures. Undifilum was identified within the parenchyma layers in seeds of Astragalus lentiginosus M.E. Jones using light microscopy and polymerase chain reaction. Astragalus lentiginosus and Oxytropis sericea Nutt. seedlings produced in embryo culture without seed coats did not contain swainsonine or fungus. Plants produced from whole seed contained U. oxytropis in both foliage and root tissues. When the in-vitro cultured plants of O. sericea and U. oxytropis cultures were subjected to environmental stresses including high temperature, low and high pH media, nutrient deficient media, and polyethylene glycol (PEG) amended media to simulate water deficit, both dry mass and swainsonine levels were affected. Swainsonine levels were greatest for O. sericea and Undifilum cultures in PEG or hydrochloric acid amended media. Plants grown in PEG-amended media had significantly greater dry mass, while Undifilum grown in PEG-amended media had lower dry mass than other treatments.

Endogenous fungi isolated from three locoweed species from rangeland in western China

“…This colonization is consistent with transmission of A.U. oxytropis, which is maternally transmitted through seed (Oldrup et al 2010). Braun et al (2003) found that slow growing Alternaria sect.…”

“…They can be readily isolated from leaves, petioles, stems, flowers and seed (Braun et al, 2003). The fungi are vertically transmitted through seed, but found only in the seed coat and underlying layer (Oldrup et al, 2010).…”

“…The fungus does not cause any obvious disease symptoms on the plant hosts and the plant host does not show a resistance response toward the fungus even at the cellular level (Reyna et al, 2012). The fungus does not deter invertebrate feeding, or aid in plant growth under heat stress or nitrogen deficiency (Thompson et al, 1995;Oldrup et al, 2010). Does Alternaria sect.…”

Heritable symbionts in a world of varying temperature

“…Overall, seeds maintained at higher temperatures, at low relative humidity and for longer periods of time were less likely to retain the infection, presumably associated with loss of fungal viability on the seed (do Valle Ribeiro, 1993). However, the impact of temperature is not universal: Oldrup et al (2010) noted that 80% of locoweed seed maintained in uncontrolled warehouse conditions over 40 years retain Undifilum endophyte infection (Oldrup et al, 2010).…”

Plant Bioactive Metabolites and Drugs Produced by Endophytic Fungi of Spermatophyta

“…The inhibitory properties on α-mannosidase have been exploited for the development of swainsonine as an anticancer drug, which has been impaired by reason of undesirable side effects [331,332]. Finally, it is interesting to note that plants of A. lentiginosus and Oxytropis sericea germinated from the embryo, which is not colonized by endophytes, were found to be fungus free and did not contain swainsonine [333]. This evidence strongly supports the hypothesis that actually its occurrence in plants may entirely derive from biosynthesis by endophytic fungal strains.…”