Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2015
Publication Date: 11/1/2015
Citation: Reed, A.J., Mazzola, M. 2015. Characterization of apple replant disease-associated microbial communities over multiple growth periods using next-generation sequencing. Phytopathology. 105:S4.117.
Technical Abstract: Replant disease in apple occurs as a result of incompletely understood and variable complexes of soil-borne pathogens that can build up over time in orchard soil. This disease limits economic viability of newly established orchards on replant sites and results in reduced productivity for the life of the orchard. Replant disease susceptible rootstock M.26 and disease-resistant rootstock G210 were planted in soil from two orchards. DNA was extracted from roots and root-associated rhizosphere soil at the end of three growing periods. The bacterial 16S rRNA gene and fungal ITS region were sequenced on the Illumina platform to characterize the microbial community, identify known and unknown potential pathogens involved and to track community changes over successive plantings. Sequencing results from the first growing period showed that potentially pathogenic Fusarium spp. were relatively rare (0.25% to 1.5% of total fungi) and contained few sequences of other known fungal pathogens. After the third growing period, the percentage of Fusarium spp. sequences was generally higher (up to >16%), and additional pathogenic species were detected including the Cylindrocarpon-like phytopathogen Ilyonectria radicicola. Agrobacterium tumefaciens was detected in root material (up to 3.5% of total bacteria) and rarely in soil. Results indicate that both rootstock genotype and rhizosphere microbiota are important factors in tolerance to replant disease.