Monitoring effects of rootstock genotype and soil treatment strategy on postharvest fruit quality in ‘Gala’ apple

Authors: Hargarten, Heidi; Mattheis, James; Honaas, Loren

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2022
Publication Date: 6/9/2022
Citation: Hargarten, H.L., Mattheis, J.P., Honaas, L.A. 2022. Monitoring effects of rootstock genotype and soil treatment strategy on postharvest fruit quality in ‘Gala’ apple. HortScience. 57(7):789–798. https://doi.org/10.21273/HORTSCI16407-21.
DOI: https://doi.org/10.21273/HORTSCI16407-21

Interpretive Summary: When an apple orchard is replanted with new trees, sometimes soil borne diseases harm or kill the new trees. Prior research at the Tree Fruit Research Lab identified soil amendments that are superior to traditional methods to control these soil borne disease microorganisms (fungi, bacteria, nematodes). These amendments work by suppressing the growth of harmful microorganisms. While it is clear that these new amendments promote tree health and improve crop yield, very little work has been done to investigate what effects the new soil amendments have on fruit quality. In a research orchard used in the previous studies we examined fruit quality at harvest, and then during long term storage which is typical for apple fruit grown in the Pacific Northwest region of North America. We found that there is no consistent effect, neither positive or negative, on fruit quality at harvest or during cold storage. This is important because the clear benefits of the new soil amendments are without apparent downsides related to fruit quality.

Technical Abstract: Production of high-quality tree fruit requires management of tree health and vigor during orchard establishment, especially with regards to soil borne pathogens. Available strategies for the mitigation of soil borne diseases include chemical fumigants, Brassicaceous seed meal (SM) soil amendments, and the use of disease resistant rootstock genotypes. It has been documented that superior disease suppression can be achieved using specific combinations of rootstock genotype and soil amendment which, in part, alter the soil microbiome. However, regardless of soil amendment strategy or rootstock genetics, sub-lethal levels of phytotoxic compounds are known to have negative effects on the reproductive output of plants. Yet the effects on fruit quality of SM amendments and the resultant restructuring of the soil microbiome are not well studied. Thus, our objective was to explore the effects of pathogen suppression strategies on at-harvest and postharvest fruit quality of ‘Gala’ apples (Malus domestica) by observing effects of both rootstock genetics [‘Malling 26’ (‘M.26’) vs ‘Geneva 41’ (‘G.41’)] and soil amendment strategy (fumigation vs SM). We observed that rootstock genotype generally appeared to have a stronger effect than soil amendment strategy on at-harvest fruit quality and postharvest outcomes.