Influence of rootstock genotype on efficacy of anaerobic soil disinfestation for control of apple nursery replant disease

Authors: HEWAVITHARANA, SHASHIKA - Washington State University; Mazzola, Mark

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2020
Publication Date: 5/9/2020
Citation: Hewavitharana, S., Mazzola, M. 2020. Influence of rootstock genotype on efficacy of anaerobic soil disinfestation for control of apple nursery replant disease. European Journal of Plant Pathology. 157:39–57. https://doi.org/10.1007/s10658-020-01977-z.
DOI: https://doi.org/10.1007/s10658-020-01977-z

Interpretive Summary: Soil-borne disease management without chemical fumigants remains a major challenge for many crop production systems including tree fruits. Anaerobic soil disinfestation (ASD) has demonstrated promise as an alternative to soil fumigation for the control of soil-borne diseases. ASD involves the generation of an anaerobic environment through a combination of flooding and addition of a carbon source to the soil system. The current studies demonstrated that ASD conducted using orchard grass as the carbon input effectively controlled apple nursery replant disease in both greenhouse and nursery field trials. ASD also was found to provide effective weed control over the initial growing season while pre-plant soil fumigation using 1,3-dichloropropene/chloropicrin failed to suppress weed development. Effective disease control and improved apple rootstock growth were attained at a level equivalent to that achieved in response to soil fumigation. All apple rootstocks evaluated, ranging from disease susceptible to tolerant, responded similarly to ASD indicating that this alternative treatment can be implemented effectively across a spectrum of apple rootstocks. The soil treatments resulted in significant changes in both the bulk soil and rhizosphere microbial communities, however these effects were prolonged in ASD-treated soils. These changes in soil microbiology had beneficial effects in terms of increasing nutrient availability to the plants as well as suppressing pathogens that incite nursery replant disease. This ASD treatment can be suggested as a potential method for effective control of nursery replant disease across a spectrum of rootstock genotypes varying in disease tolerance.

Technical Abstract: Apple replant disease (ARD) in production nurseries can negatively impact commercial viability by diminishing tree quality and potentially serving as a source of pathogen inoculum when planted into production orchards. In previous growth chamber studies, anaerobic soil disinfestation (ASD) provided effective ARD control. The current study was carried out to determine the potential for plant genotype to influence ASD disease control efficacy. The studies employed three apple rootstock genotypes including M.9 (susceptible), G.41 (moderately tolerant), and G.935 (tolerant). ASD was conducted using orchard grass as the carbon input at a rate of 10 t ha-1 or 20 t ha-1. Rootstock growth in ASD-treated soils was comparable to that attained in response to soil pasteurization or fumigation with 1,3-dichloropropene/chloropicrin and was superior to the no treatment control (NTC) in both greenhouse and nursery field trials. In greenhouse trials, root infestation by Rhizoctonia solani AG-5 and growth performance varied with rootstock genotype and soil treatment. ASD effectively reduced the quantity of pathogen DNA detected in roots and improved rootstock growth in the greenhouse trials irrespective of grass input rate. Rootstock genotype, but not soil treatment, influenced the relative incidence of root infestation by Pythium ultimum and R. solani in the nursery field trial, although not in accordance with reported tolerance to ARD. ASD conducted with grass input at 20 t ha-1 improved soil nutrient levels, especially NO3- N, and provided significant weed control in the nursery field trial. Treatments significantly altered composition of the bulk soil and rhizosphere microbiome in greenhouse trials and these effects were prolonged in ASD-treated soils. Modification of the microbiome may have been beneficial in terms of increasing nutrient availability and pathogen suppression in ARD soil thereby improving rootstock growth in general. ASD conducted with orchard grass as the carbon input was uniformly as effective as soil fumigation in the control of ARD and increase in trunk diameter increment, the primary determinant of apple rootstock value. This ASD treatment can be suggested as a potential method for effective control of nursery replant disease across a spectrum of rootstock genotypes varying in disease tolerance.