## 8 Conclusions  
In conclusion, deploying effective genetic resistance to soilborne nematode and necrotic frungal pathogens of the small-grain cereals remains a challenge. Genetic resistance is dependent on the genotypes of the host and pathogen, and can be location-dependent, as was noted for nematode  
Figure 1: Alignment of deduced amino acid sequence of DORN1 from _A. thaliana_ (derived from GenBank NM_001085304.1) with three candidate wheat orthologiques Traes_2 BS_80806 CA5F.1, Traes_2 AS_DE/DCB294.1, and Traes_1 BS_A999A190E.3. Loops are extracellular and contain ATP binding residues (blue dots). Boxes delineate a conserved transmembrane domain (TM) and kinase domains (KD). Domain KD-X is poorly conserved and is not indicated [113; 114]. resistance [7]. Nevertheless, marker technology and linkage analysis software are screens of adapted or semi-adapted cereal genotypes. Lignin accumulation and ROS were recurring defense pathways in cereal root-pathogen interactions. A second pathway for the biosynthesis of the lignin precursor 4-coumaric acid has been described in maize and _Brachypodium distachyon_. Many other grasses, including rice, wheat, and barley, harbor one to six copies of the requisite gene in their genomes [78; 125]. It is very likely that enhancement of lignin content to the right degree and at the right time in the root could protect against a range of nematode and fungal pathogens. The use of 'omics approaches for resistance gene discovery has yielded orthologous and novel parasitism genes from plant-parasitic nematodes, and remains to be fully realized for identifying parasitism genes from the fungal pathogens. Sequencing of coding regions of the genome (exome) can be applied to move from phenotype to genotype at the single polymorphism level with development of species-specific probes [65; 126; 127; 128]. With the increasing number of genome sequences available each year, the pan-genome mining approach [18] will become feasible for more host and pathogen species. One caveat of certain roots is the potential for ectopic expression of genes normally found in other organs, such as chlorophyll- and photosynthesis-related genes [67; 76; 129]. It is not clear whether the resistance interaction provides better leads for novel gene discovery than the susceptible interaction; both are informative. Many 'omics studies produced sequences lacking functional annotation (e.g., \"hypothetical protein\"). These might be considered for HIGS approaches if species- and gene-specificity are desired. Pathogen targets that are important for growth and life cycle in the host should be better HIGS candidates than those involved in the \"arms race,\" which are continually under selection. Off-target effects of the RNAi molecule will be minimized by selecting for single copies of the RNAi molecule in the host and will need to be monitored in the recipient pathogen. In most cases, the effect(s) of each candidate gene on pathogen suppression and disease severity ultimately needs testing in the field. There is no single approach guaranteed to produce a gene, genetic locus, or trait that is easy to deploy and is effective in the field. However, a variety of approaches, each with advantages and drawbacks, are available. The following are available online at [[http://www.mdpi.com/2073-4395/9/4/188/s1](http://www.mdpi.com/2073-4395/9/4/188/s1)]([http://www.mdpi.com/2073-4395/9/4/188/s1](http://www.mdpi.com/2073-4395/9/4/188/s1)), Table S1: Properties of the RNA and RNA sample libraries used in wheat root-_Pratylenchus_ transcriptomics, Table S2: Candidate IWGSC wheat _DORN1_ orthologues of Brassica GenBank accessions. Conceptualization, P.A.O. and R.M.S. ; methodology, P.A.O., A.B.P. and R.M.S. ; software, R.M.S. ; formal analysis, P.A.O. and R.M.S. ; investigation, P.A.O. and A.B.P. ; resources, P.A.O., A.B.P. and R.M.S. ; data curation, R.M.S. ; writing--original draft preparation, P.A.O. ; writing--review and editing, P.A.O., A.B.P. and R.M.S. ; visualization, P.A.O. This research was funded by USDA CRIS Project No.