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International Journal of Plant Genomics
Volume 2017 (2017), Article ID 8950746, 14 pages
Research Article

Comparative Transcriptome Analysis Reveals a Preformed Defense System in Apple Root of a Resistant Genotype of G.935 in the Absence of Pathogen

1USDA-ARS, Tree Fruit Research Laboratory, Wenatchee, WA 98801, USA
2USDA-ARS, Molecular Plant Pathology Laboratory, Beltsville, MD 20705, USA
3Tree Fruit Research Institute, Chinese Academy of Agricultural Sciences, Xingcheng, Liaoning 10081, China

Correspondence should be addressed to Yanmin Zhu

Received 14 October 2016; Revised 9 February 2017; Accepted 1 March 2017; Published 30 March 2017

Academic Editor: Anca Macovei

Copyright © 2017 Yanmin Zhu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Two apple rootstock genotypes G.935 and B.9 were recently demonstrated to exhibit distinct resistance responses following infection by Pythium ultimum. As part of an effort to elucidate the genetic regulation of apple root resistance to soilborne pathogens, preinoculation transcriptome variations in roots of these two apple rootstock genotypes are hypothesized to contribute to the observed disease resistance phenotypes. Results from current comparative transcriptome analysis demonstrated elevated transcript abundance for many genes which function in a system-wide defense response in the root tissue of the resistant genotype of G.935 in comparison with susceptible B.9. Based on the functional annotation, these differentially expressed genes encode proteins that function in several tiers of defense responses, such as pattern recognition receptors for pathogen detection and subsequent signal transduction, defense hormone biosynthesis and signaling, transcription factors with known roles in defense activation, enzymes of secondary metabolism, and various classes of resistance proteins. The data set suggested a more poised status, which is ready to defend pathogen infection, in the root tissues of resistant genotype of G.935, compared to the susceptible B.9. The significance of preformed defense in the absence of a pathogen toward overall resistance phenotypes in apple root and the potential fitness cost due to the overactivated defense system were discussed.