THE USE OF ARBUSCULAR MYCORRHIZAL FUNGI IN THE THE RESTORATION OF ENDEMIC AND INDIGENOUS HAWAIIAN PLANTS

Abstract

In Hawaii, it’s estimated that 31% of native flora is endangered due to habitat and pollinator loss, and competition from invasive species. There are widespread efforts to restore native Hawaiian plants and habitats by various organizations to mitigate this problem. These ecological restoration projects, however, often do not utilize arbuscular mycorrhizal (AM) fungi, although it is estimated that >90% of native Hawaiian plants form symbioses with them. AM fungi are a prevalent, widespread group which colonize an estimated 80% of all plant species in the world. AM fungi have been shown to benefit their host plants by increasing uptake of water and nutrients, as well as protecting against pathogens. Numerous studies have also shown their importance in ecological restoration projects outside of Hawaii. This dissertation focuses on the potential use of AM fungi in ecological restoration projects in Hawaii. I investigated the viability of AM fungal spores in 50-year-old soils collected from Hawaii Volcanoes National Park on the Island of Hawaii to inform the longevity and storage of AM fungal inoculum (Chapter 1). The viability of AM fungal spores was determined to be minimal, suggesting that 50 years is too long for storage of AM fungal inoculum. I also investigated the potential use of AM fungi and Moesziomyces aphidis, a foliar yeast, in decreasing the disease severity of Neoerysiphe galeopsidis infecting Phyllostegia kaalaensis, a critically-endangered mint native to the Waianae Mountain Range (Chapter 2). AM fungi, as well as M. aphidis and the combination of both are effective in decreasing the disease severity of N. galeopsidis infecting Phyllostegia kaalaensis, however only M. aphidis significantly so, indicating that the microbial symbionts could be used in lieu of fungicides in controlling this pathogen in the greenhouse and potentially in the wild. Finally, I sampled root tissue from 35 different native Hawaiian plants species commonly used in ecological restoration across 10 sites on the island of Oahu to detect for mycorrhizal occurrence (Chapter 3). I also calculated the percent root length colonization (PRLC) and investigated the potential effects of species and site on PRLC. Thirty-four of 35 (~97%) plant species were found to have mycorrhizal colonization, which exceeds a previous estimate of >90% of Hawaiian plants forming mycorrhizal symbioses. The presence or absence of AM fungi have been identified in 22 species of plants that were not surveyed previously. The PRLC of 5 species of plants was significantly affected by different site factors, such as mean annual precipitation and nutrient availability, that increase the root length of plants as well. Overall, these results suggest that the inoculation of AM fungi in the greenhouse should be considered in future ecological restoration projects in Hawaii.