Resistance Gene Identification, Cloning, and Characterization in Plants

Various plant diseases and diverse microbial communities, including bacteria, fungi, oomycetes, viruses, and nematodes, drastically deteriorate crop quality and yield worldwide. Plant-pathogen interaction mechanisms have been extensively studied, which involve the activation of signaling events that lead to the suppression of pathogen attacks. Several R genes have been found in plants containing conserved functional domains and nucleotide-binding sites with leucine-rich repeats (NBS-LRR). So far, different experimental approaches have been used to identify resistant genes in a variety of plant species. For example, PCR-based cloning has been employed to identify putative NB-containing R genes that help to identify potential resistance gene homologs (RGHs). Besides, multiple or complicated features connected to a single or several stress responses can be studied using genome-wide association studies (GWAS). In recent years, for the cloning and mapping of resistance gene analogues (RGAs), a sequence-homology-based approach has been extensively used. In this chapter, the identification of resistant genes, their resistance, cloning types, and the identification and characterization of RGA have been discussed. Simultaneously, the mechanisms of the different resistant genes and their functions in different crops have been reviewed. Furthermore, the RGAs that have been cloned in many different crops have been suggested as a source of genetic material for cultivars that are resistant to disease for a long time in crop-breeding programs.