Effect of rootstock genotype and arbuscular mycorrhizal fungal (AMF) species on early colonization of apple

Authors: COOK, CHRIS - Washington State University; Huskey, David; MAZZOLA, MARK - Stellenbosch University; Somera, Tracey

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2024
Publication Date: 5/16/2024
Citation: Cook, C., Huskey, D.A., Mazzola, M., Somera, T.S. 2024. Effect of rootstock genotype and arbuscular mycorrhizal fungal (AMF) species on early colonization of apple. Plants. 13(10). Article 1388. https://doi.org/10.3390/plants13101388.
DOI: https://doi.org/10.3390/plants13101388

Interpretive Summary: Roughly ~80% of all land plants are colonized by arbuscular mycorrhizal fungi (AMF), associations which are generally thought to be beneficial. Although these symbiotic root-fungal relationships are extremely pervasive, in apple, it is not clear whether some rootstock genotypes are more susceptible to AMF colonization than others. We hypothesized that some apple rootstock cultivars are generally more receptive to colonization (or are more dependent on AMF) than others and that certain AM fungal species will prefer certain rootstocks. Matching host genetics with compatible AMF species that influence tree growth is of importance for the application of management practices that are employed to improve tree establishment at planting. Studies addressing this issue are particularly relevant due to the broad availability of commercial AMF inoculants that have not been verified to form associations with apple or improve tree growth . The findings from our study indicate that optimal colonization of apple root systems occurs in a rootstock genotype-AMF species specific manner. In other words, individual apple rootstock genotypes can react very differently to colonization depending on the AMF species used. This study marks a significant step towards laying the groundwork for harnessing potential apple rootstock-AMF species preferences for integration into nursery and orchard management systems.

Technical Abstract: The effect of plant cultivar on the degree of mycorrhization and/or benefits mediated by arbuscular mycorrhizal fungi (AMF) has been documented in many crops. In apple, a wide variety of rootstocks are commercially available; however, it is not clear whether some rootstock genotypes are more susceptible to mycorrhization than others and/or whether AMF species identity influences rootstock compatibility. This study addresses these questions by directly testing the ability/efficacy of four different AMF species (Rhizophagus irregularis, Septoglomus. deserticola, Claroideoglomus claroideum or Claroideoglomus etunicatum) to colonize four commercially available apple rootstock genotypes (G.11, G.41, G.210 and G.890). Briefly, micropropagated plantlets were inoculated with individual species of AMF or were not inoculated. After 5 weeks, the effects of the interaction between rootstock genotype and AMF species on mycorrhization, plant growth and leaf nutrient concentrations were assessed. AMF treatment was a significant source of variation affecting the percentage of colonization. The highest levels of mycorrhizal colonization were obtained by G.41 x S. deserticola and G.890 x C. claroideum, although percent colonization did not reflect growth outcomes or nutritional status. In G.210, AMF species identity was associated with leaf nitrogen status as well as the plant growth response. Our findings suggest that matching host genetics with compatible AMF species has the potential to enhance agricultural practices in nursery and orchard systems.