Presentation Title

Linking mycorrhizal colonization to floral rewards, pollinator behavior, and reproductive success in highbush blueberry

Abstract

Linking mycorrhizal colonization to floral rewards, pollinator behavior, and reproductive success in highbush blueberry

This poster outlines the background, methods, and significance of our proposed work investigating the effects of mycorrhizal fungi on floral characteristics of Highbush Blueberry. We ask whether the degree of colonization with mycorrhizal fungi is associated with (1) pollen and nectar quantity and quality, (2) pollinator visitation, and (3) plant fitness. We hypothesize that mycorrhizal fungi may mediate the interaction between blueberry plants and their pollinators by influencing the volume and chemistry of floral rewards.

Background:

Mycorrhizal fungi colonize blueberry plant roots where they are partners in a mutualistic exchange; fungi provide nutrients and water to the plant and in return receive energy-storing photosynthetic products (Fellbaum et al. 2012). Mycorrhizal colonization impacts floral traits of their host plants, and consequently it may alter the behavior of pollinators that depend on these floral traits. Colonization with mycorrhizal fungi, which can be managed by inoculating seedlings with mycorrhizal fungi, can lead to increased effort into floral traits important to pollinators, such as flower and inflorescence number (Brody et al 2019). Inoculation also influences pollen and nectar production in summer squash and tomatoes (Lau et al. 1995, Poulton 2002). For multiple species of annual plants, pollinators prefer inoculated plants over non-inoculated plants (Gange and Smith 2005), and plants with higher rates of bee visitation produce more berries and larger berries, which increases revenues for farmers (Nicholson and Ricketts 2019, Courcelles et al. 2013).

Methods:

Study plants consist of forty highbush blueberry plants at Waterman Berry Farm in Johnson, VT, half of which were inoculated with mycorrhizal fungi in 2011. To determine fungal colonization, we will stain root samples with trypan blue dye and vinegar (Vierheilig et al. 1998) and count the proportion of cells in each sample containing fungal structures using microscopy (McGonigle et al. 1990). To measure pollinator visitation, we will observe each plant for 20 minutes per day at least three days per week and record the number and species of pollinators as well as the length of each visit. For a selected number of visits, we will count the number of pollen grains deposited as an additional measurement of visit effectiveness. To determine pollen limitation, we will hand-pollinate two branches of twenty plants per cultivar by collecting pollen into petri dishes and painting it onto floral stigmas. We will record the fruit set, berry size and sugar content, and the number of fertilized and unfertilized seeds in each berry.

Nectar and pollen samples will be collected from flowers after they have been bagged for 24 hours to block pollinator access to flowers. We will measure the volume of extracted nectar using a microcapillary tube and quantify sugar content using a hand-held refractometer (Kearns and Inouye, 1993). We will measure pollen quantity by collecting the anthers of the same bagged flowers into a microcapillary tube, vortexing them in the lab to allow pollen to be released, and counting the number of grains per flower. We will analyze the compound composition of nectar and pollen samples using liquid chromatography-Electrospray Ionization Mass Spectroscopy and UV spectroscopy (methods in Palmer-Young et al. 2019). All variables will be correlated to fungal colonization with an analysis of covariance to determine significant relationships between colonization and floral traits.

Significance:

The interaction between plants, fungi, and pollinators is relevant to many natural and agricultural systems. Evidence linking a plant's belowground fungal interactions to their pollinator rewards and thus their aboveground pollinator interactions would expand the frontiers of literature on mycorrhizal ecology. From an agricultural standpoint, a better understanding of the permanence of inoculation will inform its cost-effectiveness as a management technique, as seedling inoculation with mycorrhizal fungi may decrease the need for synthetic fertilizer. Data on pollen limitation can provide a measurement of plant response to declining bee populations, which is instrumental when planning for conservation of native bee populations. Finally, if plants with greater fungal colonization better attract pollinators, then native bee population decline may constitute a selective pressure for plants to increase investment in their fungal partnerships.

References:

  • Brody, A. et al., 2019. Am. J. Bot., 106, 1412-1422.

  • Courcelles, D. et al., 2013. J Appl Entomol, 137, 693-701.

  • Fellbaum, C. et al., 2012. Plant Signal Behav, 7, 1509-1512.

  • Gange, A. and A. Smith, 2005. Ecol Entomol, 30, 600-606.

  • Kearns, C., and D. Inouye., 1993. U of Colorado, Print.

  • Lau, T. C. et al., 1995. Plant Cell and Environment, 18, 169–177.

  • McGonigle, T. et al., 1990. New Phytol, 115, 495-501.

  • Nicholson, C., and T. Ricketts. 2019. Agric Ecosys Environ, 272, 29-37.

  • Ollerton, J. et al., 2011. Acta Oecol, 120, 321-326.

  • Palmer‐Young, E. et al., 2019. Ecological Monographs, 89, e01335.

  • Poulton, L. et al., 2002. New Phytologist, 154, 255–264.

  • Vierheilig, H. et al., 1998. Appl Environ Microbiol, 64, 5004.

Primary Faculty Mentor Name

Alison Brody

Graduate Student Mentors

Erin O'Neill

Faculty/Staff Collaborators

Dr. Alison Brody (Faculty mentor), Erin O'Neill (Graduate Student Mentor)

Status

Undergraduate

Student College

College of Arts and Sciences

Second Student College

College of Arts and Sciences

Program/Major

Biological Science

Second Program/Major

Environmental Sciences

Primary Research Category

Biological Sciences

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Linking mycorrhizal colonization to floral rewards, pollinator behavior, and reproductive success in highbush blueberry

Linking mycorrhizal colonization to floral rewards, pollinator behavior, and reproductive success in highbush blueberry

This poster outlines the background, methods, and significance of our proposed work investigating the effects of mycorrhizal fungi on floral characteristics of Highbush Blueberry. We ask whether the degree of colonization with mycorrhizal fungi is associated with (1) pollen and nectar quantity and quality, (2) pollinator visitation, and (3) plant fitness. We hypothesize that mycorrhizal fungi may mediate the interaction between blueberry plants and their pollinators by influencing the volume and chemistry of floral rewards.

Background:

Mycorrhizal fungi colonize blueberry plant roots where they are partners in a mutualistic exchange; fungi provide nutrients and water to the plant and in return receive energy-storing photosynthetic products (Fellbaum et al. 2012). Mycorrhizal colonization impacts floral traits of their host plants, and consequently it may alter the behavior of pollinators that depend on these floral traits. Colonization with mycorrhizal fungi, which can be managed by inoculating seedlings with mycorrhizal fungi, can lead to increased effort into floral traits important to pollinators, such as flower and inflorescence number (Brody et al 2019). Inoculation also influences pollen and nectar production in summer squash and tomatoes (Lau et al. 1995, Poulton 2002). For multiple species of annual plants, pollinators prefer inoculated plants over non-inoculated plants (Gange and Smith 2005), and plants with higher rates of bee visitation produce more berries and larger berries, which increases revenues for farmers (Nicholson and Ricketts 2019, Courcelles et al. 2013).

Methods:

Study plants consist of forty highbush blueberry plants at Waterman Berry Farm in Johnson, VT, half of which were inoculated with mycorrhizal fungi in 2011. To determine fungal colonization, we will stain root samples with trypan blue dye and vinegar (Vierheilig et al. 1998) and count the proportion of cells in each sample containing fungal structures using microscopy (McGonigle et al. 1990). To measure pollinator visitation, we will observe each plant for 20 minutes per day at least three days per week and record the number and species of pollinators as well as the length of each visit. For a selected number of visits, we will count the number of pollen grains deposited as an additional measurement of visit effectiveness. To determine pollen limitation, we will hand-pollinate two branches of twenty plants per cultivar by collecting pollen into petri dishes and painting it onto floral stigmas. We will record the fruit set, berry size and sugar content, and the number of fertilized and unfertilized seeds in each berry.

Nectar and pollen samples will be collected from flowers after they have been bagged for 24 hours to block pollinator access to flowers. We will measure the volume of extracted nectar using a microcapillary tube and quantify sugar content using a hand-held refractometer (Kearns and Inouye, 1993). We will measure pollen quantity by collecting the anthers of the same bagged flowers into a microcapillary tube, vortexing them in the lab to allow pollen to be released, and counting the number of grains per flower. We will analyze the compound composition of nectar and pollen samples using liquid chromatography-Electrospray Ionization Mass Spectroscopy and UV spectroscopy (methods in Palmer-Young et al. 2019). All variables will be correlated to fungal colonization with an analysis of covariance to determine significant relationships between colonization and floral traits.

Significance:

The interaction between plants, fungi, and pollinators is relevant to many natural and agricultural systems. Evidence linking a plant's belowground fungal interactions to their pollinator rewards and thus their aboveground pollinator interactions would expand the frontiers of literature on mycorrhizal ecology. From an agricultural standpoint, a better understanding of the permanence of inoculation will inform its cost-effectiveness as a management technique, as seedling inoculation with mycorrhizal fungi may decrease the need for synthetic fertilizer. Data on pollen limitation can provide a measurement of plant response to declining bee populations, which is instrumental when planning for conservation of native bee populations. Finally, if plants with greater fungal colonization better attract pollinators, then native bee population decline may constitute a selective pressure for plants to increase investment in their fungal partnerships.

References:

  • Brody, A. et al., 2019. Am. J. Bot., 106, 1412-1422.

  • Courcelles, D. et al., 2013. J Appl Entomol, 137, 693-701.

  • Fellbaum, C. et al., 2012. Plant Signal Behav, 7, 1509-1512.

  • Gange, A. and A. Smith, 2005. Ecol Entomol, 30, 600-606.

  • Kearns, C., and D. Inouye., 1993. U of Colorado, Print.

  • Lau, T. C. et al., 1995. Plant Cell and Environment, 18, 169–177.

  • McGonigle, T. et al., 1990. New Phytol, 115, 495-501.

  • Nicholson, C., and T. Ricketts. 2019. Agric Ecosys Environ, 272, 29-37.

  • Ollerton, J. et al., 2011. Acta Oecol, 120, 321-326.

  • Palmer‐Young, E. et al., 2019. Ecological Monographs, 89, e01335.

  • Poulton, L. et al., 2002. New Phytologist, 154, 255–264.

  • Vierheilig, H. et al., 1998. Appl Environ Microbiol, 64, 5004.