Cereal Root Interactions with Soilborne Pathogens—From Trait to Gene and Back

Patricia A Okubara,Amy B Peetz,Richard M Sharpe

doi:10.3390/agronomy9040188

Abstract

Realizing the yield potential of crop plants in the presence of shifting pathogen populations, soil quality, rainfall, and other agro-environmental variables remains a challenge for growers and breeders worldwide. In this review, we discuss current approaches for combatting the soilborne phytopathogenic nematodes, Pratylenchus and Heterodera of wheat and barley, and Meloidogyne graminicola Golden and Birchfield, 1965 of rice. The necrotrophic fungal pathogens, Rhizoctonia solani Kühn 1858 AG-8 and Fusarium spp. of wheat and barley, also are discussed. These pathogens constitute major causes of yield loss in small-grain cereals of the Pacific Northwest, USA and throughout the world. Current topics include new sources of genetic resistance, molecular leads from whole genome sequencing and genome-wide patterns of hosts, nematode or fungal gene expression during root-pathogen interactions, host-induced gene silencing, and building a molecular toolbox of genes and regulatory sequences for deployment of resistance genes. In conclusion, improvement of wheat, barley, and rice will require multiple approaches.

Highlights

Grain crops including rice (Oryza sativa L.), common or bread wheat (Triticum aestivum L.), durum wheat (Triticum turgidum L. ssp. durum), and corn (Zea mays L.) are preferred staple foods throughout many parts of the world
We focus on new genetic loci for resistance or tolerance from association mapping and genome-wide association studies (GWAS); the roles of genomics and transcriptomics in identifying specific candidate resistance and parasitism genes; advances in understanding the mechanisms by which pathogen proteins act in a susceptible host to cause the disease condition; and the difficulties of using candidate resistance genes from non-cereals to find and test the corresponding genes in small-grain cereals
Each experiment consisted of four treatments, three plants per treatment: (1) Pratylenchus neglectus only (Pn); (2) P. thornei only (Pt); (3) a 1:1 mixture of P. neglectus and P. thornei (PnPt); and (4) no-nematode control (Cont)

Summary

Introduction

Grain crops including rice (Oryza sativa L.), common or bread wheat (Triticum aestivum L.), durum wheat (Triticum turgidum L. ssp. durum), and corn (Zea mays L.) are preferred staple foods throughout many parts of the world. Durum), and corn (Zea mays L.) are preferred staple foods throughout many parts of the world. Yield enhancement of these crops poses a challenge for growers and breeders who seek to maintain production rates in accordance with consumer needs and in the face of environmental challenges. Smith) Sacc., Pratylenchus neglectus (Rensch, 1924) Filijev and Stuurmans Stekhoven, 1941, P. thornei Scher and Allen, 1953, Hereodera avenae Wollenweber, 1924, and Meloidogyne graminicola These pathogens are problems in the dryland production regions of the Pacific Northwest, USA (PNW), Australia, Europe, China, Southeast Asia, India, and other parts of the world [2,3,4,5,6,7]. A body of knowledge is accumulating about the cellular and molecular interactions between these hosts and pathogens that are helping to elucidate the basis of susceptibility and resistance, e.g., References [8,9,10,11,12,13]

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