Location: Physiology and Pathology of Tree Fruits Research
Project Number: 2094-21220-003-012-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Aug 1, 2023
End Date: Jul 31, 2026
Objective:
Identify potentially beneficial roles of specific apple rootstock-AMF associations including acquistion of soil nutrients, protection against root pathogenic fungi, and tolerance to water stress.
Approach:
Arbuscular Mycorrhizal Fungi (AMF) have been shown to provide a spectrum of benefits to their plant hosts including improved tolerance to water stress, improved access to nutrients and disease resistance. However, these functional benefits may be fungus- and plant-species dependent. This research will assess the ability of specific (compatible) apple rootstock/AMF associations to 1) alleviate water stress in dwarfing apple rootstocks, 2) improve host plant ability to acquire nitrogen from soil, and 3) suppress infection of apple roots by Rhizoctonia solani AG-5, a soil-borne fungal pathogen involved in apple replant disease. It has been shown that water transport by mycorrhizal fungi may improve plant access to available soil water under drying conditions. In the first experiment, we will explore the ability of a commercially prepared R. irregularis AMF inoculum to provide tolerance to short-term water stress in the dwarfing apple rootstock G.11. Plants will be maintained in a water-stressed state (50% field capacity) for up to 4 weeks and plant physiological responses will be measured on a daily basis. Under water-stressed conditions, plants colonized by R. irregularis are expected to be less affected than those without R. irregularis. However, in well-watered soil (non-stressed control) plant physiological responses are not expected to be different between the two treatments. In a second experiment, the ability of specific rootstock/AMF associations to enhance plant defense against subsequent pathogen infection will be tested by challenging mycorrhizal and non-mycorrhizal tissue-cultured plantlets with the fungal replant pathogen Rhizoctonia solani AG-5. Compatible rootstock genotype/AMF combinations will be selected based on data from research previously conducted in the ARS lab. Upon harvest, the amount of R. solani DNA per gram of root tissue will be quantified using a previously developed real-time quantitative polymerase chain reaction (qPCR) assay. In order to assess the influence of AMF on soil nutrient uptake under stressful conditions, both experiments will be conducted under 15N stable isotope labeling. These experiments are expected to provide clear evidence of AMF species directly functioning in beneficial roles with commercially available apple rootstock genotypes and will provide insight into specific AMF-rootstock relationships which could be harnessed to improve disease control, drought tolerance and sustainability.
