Brassica seed meal soil amendments transform the rhizosphere microbiome and improve apple production through resistance to pathogen reinfestation

• Published in: Phytopathology 2015-04, Vol.105 (4), p.460-469
• Main Authors: Mazzola, Mark, Hewavitharana, Shashika S, Strauss, Sarah L
• Format: Article
• Language: English
• Subjects: Allyl Compounds - pharmacology; Animals; Base Sequence; High-Throughput Nucleotide Sequencing; Hydrocarbons, Chlorinated - pharmacology; Malus - drug effects; Malus - growth & development; Malus - immunology; Malus - microbiology; Microbiota; Molecular Sequence Data; Mustard Plant - chemistry; Plant Diseases - immunology; Plant Diseases - microbiology; Plant Roots - drug effects; Plant Roots - growth & development; Plant Roots - immunology; Plant Roots - microbiology; Plant Stems - drug effects; Plant Stems - growth & development; Plant Stems - immunology; Plant Stems - microbiology; Pythium - physiology; Rhizosphere; Seeds - chemistry; Sequence Analysis, DNA; Sinapis - chemistry; Soil; Soil Microbiology; Tylenchoidea - physiology; Washington
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/PHYTO-09-14-0247-R

Brassicaceae seed meal (SM) formulations were compared with preplant 1,3-dichloropropene/chloropicrin (Telone-C17) soil fumigation for the ability to control apple replant disease and to suppress pathogen or parasite reinfestation of organic orchard soils at two sites in Washington State. Preplant soil fumigation and an SM formulation consisting of either Brassica juncea-Sinapis alba or B. juncea-B. napus each provided similar levels of disease control during the initial growing season. Although tree growth was similar in fumigated and SM-amended soil during the initial growing season, tree performance in terms of growth and yield was commonly superior in B. juncea-S. alba SM-amended soil relative to that in fumigated soil at the end of four growing seasons. SM-amended soils were resistant to reinfestation by Pratylenchus penetrans and Pythium spp. relative to fumigated soils and corresponded with enhanced tree performance. Phytotoxic symptoms were observed in response to SM amendment at one of two orchard sites, were dependent upon season of application, and occurred in an SM formulation-specific manner. After 2 years, the rhizosphere microbiome in fumigated soils had reverted to one that was indistinguishable from the no-treatment control. In contrast, rhizosphere soils from the SM treatment possessed unique bacterial and fungal profiles, including specific microbial elements previously associated with suppression of plant-pathogenic fungi, oomycetes, and nematodes. Overall diversity of the microbiome was reduced in the SM treatment rhizosphere, suggesting that enhanced "biodiversity" was not instrumental in achieving system resistance or pathogen suppression.