Cellular and Transcriptional Responses of Resistant and Susceptible Cultivars of Alfalfa to the Root Lesion Nematode, Pratylenchus penetrans.

Paulo Vieira,Lev G. Nemchinov,Jonathan Shao,Joseph Mowery,Jonathan D. Eisenback

doi:10.3389/fpls.2019.00971

Abstract

The root lesion nematode (RLN), Pratylenchus penetrans, is a migratory species that attacks a broad range of crops, including alfalfa. High levels of infection can reduce alfalfa forage yields and lead to decreased cold tolerance. Currently, there are no commercially certified varieties with RLN resistance. Little information on molecular interactions between alfalfa and P. penetrans, that would shed light on mechanisms of alfalfa resistance to RLN, is available. To advance our understanding of the host–pathogen interactions and to gain biological insights into the genetics and genomics of host resistance to RLN, we performed a comprehensive assessment of resistant and susceptible interactions of alfalfa with P. penetrans that included root penetration studies, ultrastructural observations, and global gene expression profiling of host plants and the nematode. Several gene-candidates associated with alfalfa resistance to P. penetrans and nematode parasitism genes encoding nematode effector proteins were identified for potential use in alfalfa breeding programs or development of new nematicides. We propose that preformed or constitutive defenses, such as significant accumulation of tannin-like deposits in root cells of the resistant cultivar, could be a key to nematode resistance, at least for the specific case of alfalfa-P. penetrans interaction.

Highlights

Alfalfa (Medicago sativa L.) has recently become the third most valuable field crop in the United States of America, with an estimated worth of over $9.3 billion, $1.2 billion more than wheat, according to the National Alfalfa and Forage Alliance (NAFA1)
Primers were designed using the online Realtime PCR tool (Integrated DNA Technologies, Inc., San Diego, CA, United States10) and alfalfa sequences generated in this work. cDNA for Quantitative real-time PCR (qPCR) analyses was made using the SuperScriptTM III First-Strand Synthesis System with oligo d(T) (Thermo Fisher Scientific) and the same RNA samples that were used for RNA sequencing
Several important conclusions can be drawn from the findings of this investigation: (1) Accumulation of tannin-like deposits (TLDs) was consistently detected in the root cells of non-infected cv

Summary

Introduction

Alfalfa (Medicago sativa L.) has recently become the third most valuable field crop in the United States of America, with an estimated worth of over $9.3 billion, $1.2 billion more than wheat, according to the National Alfalfa and Forage Alliance (NAFA1). Nematodes are one of the major limiting factors in alfalfa production, inflicting significant damage to the plants (Westerdahl and Frate, 2008). Alfalfa Response to Root Lesion Nematode root lesion nematode (RLN), Pratylenchus penetrans, a migratory endoparasitic species that attacks a broad range of crops (Hafez et al, 2006; Jones et al, 2013). High levels of infection with RLN can reduce forage yields and lead to decreased cold tolerance (Baldridge et al, 1998; Samac et al, 2015). Young plants often die, because the plant’s ability to take up water and nutrients is reduced (Fosu-Nyarko and Jones, 2016; Westerdahl et al, 2017)

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