|HOME SCHEDULE AUTHOR INDEX SUBJECT INDEX|
Intra- and inter-specific variation of infectivity of isolates of several species of mycorrhizal fungi in response to aluminum exposure.
Kelly, Charlene*,1, Morton, Joseph1, Cumming, Jonathan1, 1 West Virginia University, Morgantown, WV
ABSTRACT- ABSTRACT: Mycorrhizal fungi (AMF) mediate interactions between plants and soils, especially where nutrient or metal concentrations limit plant growth. Variation in fungal response to specific soil conditions may influence stress tolerance conferred to the host plants. Broomsedge (Andropogon virginicus) colonizes extreme sites, including acidic soils where aluminum (Al) is phytotoxic. Aluminum resistance in Broomsedge is associated with colonization by acid-adapted AM fungus Glomus clarum. These studies were extended by assessing inter- and intraspecific variation of several species of mycorrhizal fungi in their ability to confer Al resistance to Broomsedge. Broomsedge seeds were planted in sand culture inoculated with 5 isolates of 3 species of fungi (Glomus clarum, Scutellospora heterogama, and Acaulospora morrowiae). Plants were exposed to 0 or 400 M Al nutrient solution and grown for 4 or 9 weeks. Mycorrhizal infection percentage (MIP) and biomass were measured. Al effects on infection depended on fungal species. Isolate-dependent variation of colonization within species was detected in 4-week-old plants. Of the Glomus isolates tested, all exhibited increased colonization response to Al, yet only one Scutellospora isolate showed increased infection. All isolates of Acaulospora were negatively impacted by Al. However, this intra-specific variation was not seen in plants grown 9 weeks.Biomass response to Al in young plants was isolate-specific, whereas, plants grown for 9 weeks did not exhibit isolate-dependent responses in biomass. This variation in Al response in young plants may reflect spore germination inhibition by Al. Some Al-sensitive isolates exhibited increased tolerance in age, reflecting secondary colonization of roots by more tolerant hyphae. These patterns may be attributed to selection of Al-resistant hyphal lines under Al exposure.
Key words: variation, mycorrhizal fungi, aluminum