Genetics and utilization of pathogen resistance in plants

• Published in: The Plant cell 1996-10, Vol.8 (10), p.1747-1755
• Main Authors: Crute, I.R. (Horticulture Research International, Warwick, UK.), Pink, D.A.C
• Format: Article
• Language: English
• Subjects: AGENT PATHOGENE; Alleles; AMELIORATION DES PLANTES; avirulence genes; avr genes; DISEASE RESISTANCE; DOMINANCE; ENFERMEDADES DE LAS PLANTAS; Erysiphe graminis; FITOMEJORAMIENTO; GENE; gene for gene relationship; GENES; Genetic loci; GENETICA; GENETICS; GENETIQUE; LITERATURE REVIEWS; LOCI; LOCUS; MALADIE DES PLANTES; Medical genetics; Melampsora lini; Mildews; ORGANISMOS PATOGENOS; Parasite hosts; PATHOGENS; PLANT BREEDING; Plant cells; PLANT DISEASES; PLANTAS; PLANTE; PLANTS; Puccinia graminis; Puccinia recondita; Puccinia striiformis; r genes; RESISTANCE AUX MALADIES; resistance genes; resistance loci; Resistance Responses; RESISTENCIA A LA ENFERMEDAD; Rust fungi; Triticum aestivum
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.8.10.1747

Until relatively recently, knowledge of plant resistance to pathogens has resulted primarily from research associated with the selective breeding of crop species. Although resistance is well described at the cellular, whole plant, and population levels in terms of genetics, histology, and associated biochemistry, a full mechanistic understanding of how pathogen resistance is mediated in plants is only now becoming feasible as a result of the isolation and sequencing of several putatively interacting plant and pathogen genes. Nevertheless, plant resistance genes have been used beneficially in agriculture for decades, even though their effects have not always been durable. This review provides a short and selective overview of the genetics of pathotype-specific resistance in plants, its past utilization in crop improvement, and some indications of how recent advances may impact the future. Reference to data obtained from investigations with a few well-studied host-pathogen combinations is used to develop some general themes. It is becoming evident that plant genomes contain a large number of genes that are apparently involved in the detection and discrimination of potential pathogens. Furthermore, these genes are commonly clustered in complex loci, sometimes comprising genes involved in resistance to taxonomically unrelated pathogens. The genetics of specific pathogen recognition is complex. For example, in wheat >90 genes that condition isolate-specific resistance to three rust species (Puccinia striiformis, P. recondita, and P. graminis) and powdery mildew (Erysiphe graminis) have been identified. Only one of these genes (Lr20/Sr15) is thought to be involved in the recognition of more than one pathogen species. For some genes, alleles with different pathotype specificity have been identified; there is also evidence that genes expressing identical specificity are present at different loci in the same plant species as well as in different species. It seems likely, then, that resistance genes are members of substantial multigene families, potentially well conserved among taxa. Evidence is also accumulating that novel discriminating capability may be generated at these complex loci by recombination or gene-conversion events. The existence of plant genes providing resistance to pathogens was demonstrated soon after the rediscovery of Mendel's seminal studies on inheritance. Biffen demonstrated that a single locus was responsible for the resistance of some wheat