Progress report for GNC20-302
This study, “Effects of Ericoid mycorrhizal fungi (ErMF) on performance of V. macrocarpon under abiotic stresses related to climate change & assessment of ErMF diversity in cultivated and wild cranberry settings,” endeavors not only to encourage sustainable agricultural practices but to expand stress tolerance of cranberry crops, thereby easing challenges faced by growers. Cranberry (Vaccinium macrocarpon Ait.) growers are under increasing pressure as a result of climate change, which is affecting cranberry production through repeated cycles of water and heat stress. These climatic events are well-established and predicted to intensify. Cranberry vines have evolved in a unique ecosystem (bog) and are highly susceptible to water and heat stress. Hoping to ameliorate the effects of these abiotic stressors and reduce the negative effects on yield and fruit size, growers tend to over-fertilize and irrigate vines. However, these practices have widely-documented negative impacts on water quality of the surrounding wetlands with no benefit on fruit production. Multiple studies conducted in blueberry have shown that inoculation with ericoid mycorrhizal fungi (ErMF) have a reductive effect of abiotic stressors, improving plant vigor. ErMF are ubiquitous, with local strains already present and active in agricultural soils, such as the cranberry production system.
The identification of ErMF strains in wild cranberry, which grow under more stressful conditions than cultivated, might provide opportunities for selection of strains that could be used for inoculation in commercial production settings, with the potential to provide stress mitigation benefits.
The role of ericoid mycorrhizae in Nitrogen uptake in cranberry production is well known. However, the potential role ErMF play in Phosphorus uptake is not well understood. Although cranberry are not heavily fertilized with P, contamination from phosphorus agricultural runoff poses risk to the quality of surrounding waterways.
Inoculation with ErMF may stretch cranberry’s range of tolerance, allowing growers to lessen water and fertilizer usage in response to climate change impacts. The main objectives of this study are: (1) evaluation of ErMF biodiversity in cultivated marshes and wild cranberry across WI; (2) Establish the role of ericoid mycorrhizal fungi (ErMF) Rhizoscyphus ericae strains on organic Phosphorus uptake; and (3) Assessment of ErMF’s impact on water stress response in cranberry plants.
Upon root development in the hydroponics system, cuttings in each condition will be inoculated with mycelial strands from liquid culture of mycorrhizal fungi (ATCC 32985, consistent with the ErMF used in previous studies on N uptake). Colonization will be verified after a set incubation period. Once confirmed, we will subject ErMF (+) and (-) plants to growing conditions required for assessment of (1) organic P uptake and (2) water stress.
Project outcomes will include increased researcher understanding of how ErMF affect vine performance in cranberry and evaluation through the presentation of findings. Growers will be surveyed before and after presentations to gauge their knowledge of the direct and indirect impacts of ErMF on crops and the environment; we expect to significantly increase grower interest in this new tool for sustainability, particularly given concrete benefits for growers and the environment, lowering requisite water and fertilizer usage.
We've involved five growers in our study. We've used their commercial marshes to sample soil and root tissue for the survey of diversity in Ericoid mycorrhizal fungi. We selected these growers because of their geographical distribution and the types of soils in their respective marshes. In addition, some of these locations have wild cranberry growth nearby.
Objective 1: In order to establish a baseline for the diversity of ErMF in both cultivated cranberry beds and wild bogs, in Fall 2020, we sampled from five commercial cranberry marshes of varied soil conditions and textures across the state of Wisconsin. From these soil core samples, we surface-sterilized cranberry roots and plated select segments onto agar. This provided us with fungal growth from only the inside of the cranberry root, where ErMF and other endophytes reside. This process resulted in 76 fungal isolates, 71 of which survived the isolation process. We performed DNA extractions on these isolates, and initial Sanger sequencing data has indicated several candidates for ErMF status.
Objective 2: We developed a system of axenic root growth in cranberry cuttings using hydroponics and are currently trialing methods of inoculation. This system of root development differs from standard cranberry cutting methods in that it provides us with roots free of media entanglement, an ongoing issue with the extremely fine ericoid roots. We also developed a liquid culture protocol for fungal growth in order to streamline the inoculation process with less compacted mycelial mass. We are currently testing three distinct inoculation methods: (1) hydroponic mesh sachets; (2) test tubes of nutrient solution; and (3) germination paper on agar plates. All three inoculation methods encourage connection of developing roots and mycelia by maintaining close proximity and minimizing disruption.
Educational & Outreach Activities
Honeyball, B. and Atucha. A. 2021. Ericoid Mycorrhizal Fungi & Cranberry: Mutualisms with Potential. Cranberry Crop Management Journal. Vol. 34, Issue 4.
Honeyball, B. Zalapa, J. and Atucha. A. 2022. Super roots for super fruits? Ericoid mycorrhizal fungi in association with Vaccinium macrocarpon. Wisconsin Cranberry School (Virtual). January 19, 2022.