Plant Immunity to Necrotrophs Tesfaye Mengiste Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907; email: mengiste@purdue.edu Annu. Rev. Phytopathol. 2012. 50:267–94 First published online as a Review in Advance on June 15, 2012 The Annual Review of Phytopathology is online at phyto.annualreviews.org This article’s doi: 10.1146/annurev-phyto-081211-172955 Copyright c  2012 by Annual Reviews. All rights reserved 0066-4286/12/0908-0267$20.00 Keywords immune responses, molecular mechanisms, necrotrophic pathogens, innate immunity Abstract Plants inhabit environments crowded with infectious microbes that pose constant threats to their survival. Necrotrophic pathogens are noto- rious for their aggressive and wide-ranging virulence strategies that promote host cell death and acquire nutrients for growth and repro- duction from dead cells. This lifestyle constitutes the axis of their pathogenesis and virulence strategies and marks contrasting immune responses to biotrophic pathogens. The diversity of virulence strate- gies in necrotrophic species corresponds to multifaceted host immune response mechanisms. When effective, the plant immune system dis- arms the infectious necrotroph of its pathogenic arsenal or attenu- ates its effect, restricting further ingress and disease symptom devel- opment. Simply inherited resistance traits confer protection against host-specific necrotrophs (HSNs), whereas resistance to broad host- range necrotrophs (BHNs) is complex. Components of host genetic networks, as well as the molecular and cellular processes that mediate host immune responses to necrotrophs, are being identified. In this re- view, recent advances in our understanding of plant immune responses to necrotrophs and comparison with responses to biotrophic pathogens are summarized, highlighting common and contrasting mechanisms. 267 Annu. Rev. Phytopathol. 2012.50:267-294. Downloaded from www.annualreviews.org by University of Kentucky on 09/29/14. For personal use only.