Fungal and fungal mycorrhizal traits | Hypothesized symbiotic effects | AM fungi | Plant | Soil* | Qualitative/quantitative (unit) | References - methods on how to measure the traits | References** |
Spores | | | | | | | |
Number | -fitness/competitive ability -dispersal -carbon storage | x x x | | x | Quantitative: number of spores/g soil Spores/meter of mycelia | Spores extracted by wet-sieving ((Gerdemann & Nicolson, 1963)) and sucrose gradient centrifugation (Ba, 1982) and counted under dissecting microscope | (Bever et al., 1996), (Chaudhary et al., 2020) |
size - diameter | -fitness/competitive ability -dispersal -energy to support hyphal growth in absence of host -carbon storage -resistance to abiotic and biotic stress | x x x x x | | x x | Quantitative: size measured in µm | Spore diameter measured intact in water using a dissecting or optical microscope ((Morton, 1995, 1996)) | (Chaudhary et al., 2020; Deveautour et al., 2020) |
germination rate % of total | -fitness/competitive ability -carbon storage | x | | x | Quantitative: % of germination | (Douds & Schenck, 1991), Spores over filter paper in a soil-filled Petri plate (Koske, 1981) | (Tommerup, 1983), (Maia & Yano-Melo, 2001) |
germination timing | -fitness/competitive ability -resistance to abiotic and biotic stress | x x | | x x | Quantitative - % germination per unit of time Qualitative - stratification needed | (Koske, 1981) | (Tommerup, 1984, 1985), (Koske et al., 1996) (Douds & Schenck, 1991) (Juge et al., 2002) |
color | - dispersal - palatability - UV protection - germination duration | x x | | | Qualitative: color based on CMYK color chart Quantitative: RGB color channels extracted from digitized images (JPG, TIF), calculation of luminance and saturation | Spores observed under a dissecting microscope and compared with color chart (Morton, 1996) or imaged and analyzed using computer software (Deveautour et al. 2020) | Deveautour et al. (2020),(Zanne et al., 2020) |
ornamentation | -dispersal -resistance to abiotic and biotic stress | x x | | x | Qualitative: type of ornamentation. Quantitative: size in µm | Spores mounted on slides and observed under microscope Koske and Walker, 1985 | Chaudhary et al. (2020) |
wall thickness | - dispersal -palatability - carbon storage - resistance to abiotic and biotic stress | x x x | | x | Quantitative: thickness in µm | Spores mounted on slides and thickness measured under microscope Morton (1995, 1996) | (Pawlowska et al., 1999) (Moore et al., 1985) |
wall number | -dispersal -resistance to abiotic and biotic stress | x x | | x | Quantitative: number of walls | Spores mounted on slides and observed under microscope Morton (1995, 1996) | (Walker, 1983) |
sporocarps | -dispersal | x | | x | Size and existence of fungal peridium on the sporocarp surface. | Sporocarps are measured under a microscope for size (Redecker et al., 2007) and existence of peridium (Schüßler et al., 2011) | (Mangan & Adler, 2002) |
wall chemical receptors | - perception of host/soil environmental cues affecting germination | x | x | | | Knowledge gap (develop a method to identify specific receptors) | Knowledge gap (are there specific receptors on the spore wall that trigger germination?) |
Spore nuclear content | -spore viability and germination - colonization ability after dispersal | x x | x x | x | Number of nuclei per spore | Confocal microscopy, Flow cytometry | (Kokkoris et al., 2020, 2021) (Bianciotto et al., 1995; Marleau et al., 2011) |
Elemental composition | -Energy support for hyphal growth | x | | x | Elemental composition | Proton-induced X-ray emission | (Hammer et al., 2011) |
Extraradical Hyphae | | | | | | | |
length | – nutrient/water acquisition -carbon storage -soil aggregation -plant productivity -resistance to abiotic and biotic stress | x x x x | x x x x x | x x x x x | Quantitative: hypha length in m/g dry soil | (Miller et al., 1995) | (Wilson et al., 2009) (Johnson et al., 2015) |
architecture (branching rate, anastomoses rate, absorptive/runner hypha) | – nutrient/water acquisition -carbon storage -soil aggregation -plant productivity -resistance to abiotic and biotic stress | x x x x x | x x x x x | x x x x | Qualitative Quantitative: Using image analysis in in vitro systems | (Friese & Allen, 1991) or (Bago et al., 1998b) in monoxenic conditions (Hammer et al., 2023) | Knowledge gap (e.g., is hyphal architecture akin to root architecture for nutrient acquisition? how does hyphal architecture influence soil aggregate stability?) |
inter-host connection | - transfer of nutrient/water/signals among hosts -resistance to abiotic and biotic stress | x x | x x | x | Quantitative: amount of nutrient/signal transferred Number of hosts connected by the same fungus | (Weremijewicz & Janos, 2019) (Frey & Schüepp, 1993) | Knowledge gap (e.g., are there fungi that interconnect more hosts than others? can common mycorrhizal networks provide additional pathogen protection?) |
hyphal diameter | –carbon storage - resistance to abiotic and biotic stress - palatability | x x x | x | x | Quantitative: in µm | (Friese & Allen, 1991) | (Klironomos & Kendrick, 1996) |
growth rate | – nutrient/water acquisition - carbon storage - resistance to abiotic and biotic stress | x x x | x x x | x x | Quantitative: hyphal growth in mm/day | (Schütz et al., 2022) | (Jakobsen et al., 1992b) |
hyphal lifespan/turnover | - carbon storage - nutrient/water acquisition | x x | x x | x x | Qualitative | (Pepe et al., 2018) | (Pepe et al., 2018) |
Genetic organization/hyphal fusion (homokaryon/dikaryon) (note: also applies to spores) | -fitness – nutrient/water acquisition -carbon storage -soil aggregation -plant productivity -resistance to abiotic and biotic stress - hyphal network interconnectedness | x x x x x x x | x x x x x x | x x x | Quantitative ddPCR: number of nuclei? | (Cornell et al., 2022) | (Cornell et al., 2022) (Serghi et al., 2021) |
Exudation rate/leakiness | -carbon storage -influence soil pH and fertility -soil aggregation -resistance to abiotic and biotic stress | x x x x | x x x x | x x x | Quantitative: measure release of a molecule in µM | (Tawaraya et al., 2006) | (Tawaraya et al., 2006) |
absorptive capacity | – nutrient/water acquisition | x | x | x | Quantitative: mol m-1 s-1 or % of nutrient taken up | (Frey & Schüepp, 1993), (Jakobsen et al., 1992a) | (Frey & Schüepp, 1993) |
color | -resistance to abiotic and biotic stress | x | x | | Qualitative: color described by CMYK model | (de la Providencia et al., 2005) using transformed roots and (Koske, 1981) using spores over filter paper on soil-filled Petri plate | Knowledge gap (are darker hyphae, more melanized, more resistant to fungivores?) |
wall/membrane chemical composition | -resistance to abiotic and biotic stress -nutrient/water acquisition -fungal recognition (anastomosis) -palatability | x x x x | x | x x | Quantitative: in µg | (Bethlenfalvay et al., 1981) for chitin. (Frey et al., 1992, 1994) for chitin and ergosterol (Butler & Lachance, 1986) for melanin; (Harrison & Vanbuuren, 1995) for P transporters | (Deveautour et al., 2020) |
pattern of anastomosis | - fungal recognition - fitness | x x | | | Quantitative: number of anastomosis per hyphal length (cm) or percentage of anastomosis (%) | (de la Providencia et al., 2005) | (de la Providencia et al., 2005) |
Intraradical Hyphae | | | | | | | |
-hyphal thickness | -Resource flux/exchange -resistance to abiotic and biotic stress | x x | x x | | Quantitative: in µm | (Abbott, 1982) | Knowledge gap (e.g., are thicker hyphae more resistant to pathogens? Is there a tradeoff between nutrient transfer and biotic resistance in terms of hyphal thickness?) |
-pattern of colonization (localized / widespread) | -Resource flux/exchange -resistance to abiotic and biotic stress | x x | x x | | Qualitative | (Dickson, 2004) (McGONIGLE et al., 1990) (Abbott, 1982) | Knowledge gap (e.g., is resource exchange more/less efficient when colonization is localized or widespread?) |
-rate of root colonization | -Resource flux/exchange -resistance to abiotic and biotic stress | x | x | | Quantitative: % of root colonization over time | (Dickson, 2004) | (Campo et al., 2020) |
Arbuscules | | | | | | | |
- architecture (Paris/Arum type) | - resource flux/exchange -resistance to abiotic and biotic stress | x x | x x | | Qualitative | (Dickson, 2004) | (van Aarle et al., 2005) |
- turnover rate | -resource flux/ exchange | x | x | | Quantitative: number of days | (Alexander et al., 1989)), (Toth & Miller, 1984) | Knowledge gap (e.g., are some arbuscules more short lived than others? How does arbuscule turnover affect resource exchange?) |
-number | -resource flux/ exchange | x | x | | Quantitative: number of arbuscules | Quantification of Arbuscules Using Morphometric Cytology - (Toth, 1992) Magnified intersections method - (McGONIGLE et al., 1990) Image analysis - (Smith & Dickson, 1991) Direct count - (Menge et al., 1978) | (Koch et al., 2017) |
Vesicles | | | | | | | |
-size and form (globose/lobbed) | - carbon storage - resistance to abiotic and biotic stress | x x | x x | | Quantitative: in µm (for size). Qualitative (for form) | (Abbott, 1982) | Knowledge gap (e.g., are fungi with larger vesicles more resistant to stress?) |
-number | - carbon storage | x | x | | Quantitative: number per root length | (Abbott, 1982), (Menge et al., 1978) | (Kobae et al., 2016) |
-chemical composition (C/lipid storage) | - carbon storage | x | x | | Quantitative: % total lipids/ fatty acids | (Jabaji-Hare et al., 1984) | (Jabaji-Hare et al., 1984) |
Turnover rate | - carbon storage | x | x | x | Quantitative: number of days | Knowledge gap (adapt the method used for arbuscules) | Knowledge gap (e.g., are some vesicles more short lived than others? How does vesicle turnover affect C storage?) |
Other genetic traits | | | | | | | |
Genome size | -reproductive rate - survival | | | | | Whole genome sequencing Flow cytometry | Sperschneider et al., 2023 (Hosny et al., 1998) |
GC content of the genome | - mycorrhizal host response -host preference | x | x x | x | | Whole genome sequencing Knowledge gap (missing genomes across phylogeny) | (Malar C et al., 2022) |