Honey mushrooms (Armillaria gallica) are an important group of fungi that decompose and help recycle dead plant tissue from forest trees. However, they can also cause tree diseases by becoming pathogenic when hosts are weakened by environmental stress. Other investigators have shown that single honey mushroom individuals have the potential to remain genetically stable for long periods and to grow larger and live longer than almost any other known organism. Research in the Peabody lab has shown that the honey-mushroom life cycle is unusual because some genetic individuals are genetic mosaics composed of single chromosome copy (haploid) cell lines that are genetically different from one another. Other honey-mushroom individuals have been shown to be non-mosaics, composed of two chromosome copies (diploid) cell lines that are genetically similar to one another. This leads to the hypothesis that genetic mosaicism may provide individuals with an unusual mechanism for interacting with other organisms and with their physical environment. By a process of within-individual, cell line selection, individuals may have the capacity to continuously remodel themselves in response to changes in the environment. This project will combine field collections, nuclear DNA measurements, molecular markers, and quantitative-trait analysis on individual cell-lines to measure the relative frequencies of mosaic and non-mosaic individuals in nature along a 179-km transect from Princeton, MA to Plymouth, MA. A representative sample of mosaic and non-mosaic cell lines will then be compared for genetic variability in several fitness-related, quantitative traits: growth, density of fungal filaments (hyphae), plasticity, and competitive ability under controlled laboratory conditions. Broader impacts of the project include: (1) promotion of teaching, training, and learning among undergraduates, including those who belong to underrepresented groups, (2) enhancement of infrastructure for research and education at Stonehill College and neighboring institutions, and (3) improving our understanding of the biology of an organism that serves as a major recycler and occasional pathogen in forest ecosystems.
