|WANG, LIKUN - Washington State University|
|LEISSO, RACHEL - Former ARS Employee|
|HEWAVITHARANA, SHASHIKA - California Polytechnic State University|
Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2020
Publication Date: 2/25/2020
Citation: Mazzola, M., Graham, D.L., Wang, L., Leisso, R., Hewavitharana, S.S. 2020. Application sequence modulates microbiome composition, plant growth and apple replant disease control efficiency upon integration of anaerobic soil disinfestation and mustard seed meal amendment. Crop Protection. 132. https://doi.org/10.1016/j.cropro.2020.105125.
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) and Brassica seed meal (SM) soil amendments have 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. Brassica SM amendment can provide disease control through both chemical and biological means. The current studies examined the potential to enhance overall disease control, and reduce treatment cost, by integration of these two methods. Integration of the methods in a ASD followed by SM application sequenced suppressed the generation of chemistries derived from SM that are essential for optimal levels of disease control. Although application sequence influenced the relative level of replant disease control that was achieved, independent application of ASD or SM soil amendment was as effective or superior to any of the integrated treatments in controlling this disease. When grass was utilized as the ASD carbon input, significant levels of phytotoxicity were observed indicating that a longer period between completion of the ASD application period used in this study (three weeks) and planting of apple would be required to attain effective use of this treatment. The findings indicate that under the experimental conditions employed, integration of ASD with mustard seed meal amendment is unlikely to yield additive or synergistic levels of apple replant disease control.
Technical Abstract: Anaerobic soil disinfestation (ASD) and mustard seed meal (MSM) amendments can provide effective control of soil-borne diseases including apple replant disease. These measures rely on both chemical and biological modes of action to yield effective disease control and their integration may prove beneficial or, alternatively, deleterious to overall treatment efficacy when applied in concert. Potential outcomes of integrating ASD with MSM amendments were assessed by determining the effect of treatment application sequence and ASD carbon source on generation of MSM derived allyl isothiocyanate (AITC), structure of the rhizosphere and soil microbiome, control of apple replant pathogens, and plant growth. In bioassays conducted using ‘Gala’ apple seedlings, application of ASD or MSM treatment independently was as effective or superior to all integrated treatments for the control of replant pathogens. Application of ASD prior to MSM amendment diminished the yield of AITC attained in response to soil incorporation of the Brassica juncea:Sinapis alba seed meal. Treatment application sequence had significant effect on structure of the bulk soil fungal and bacterial community. Correspondingly, treatment application sequence significantly altered plant growth performance when orchard grass was utilized as the ASD carbon input. At harvest, rhizosphere fungal but not bacterial community composition was significantly altered in treated soil relative to the control, and sequence of treatment application had significant effect on rhizosphere fungal community structure. Failure of integrated treatments to enhance disease control may have resulted from many factors including reduced generation of active metabolites, diminished activity of mechanisms functional in pathogen suppression, or the elevated accumulation and retention of phytotoxic chemistries that would require extended plant back periods. The findings indicate that under the experimental conditions employed, integration of ASD with MSM amendment is unlikely to yield additive or synergistic levels of apple replant disease control.