Involvement of nonhost resistance genes in disease resistance plausible for future crop improvement

A plant species is infected by handful of pathogenic organism despite the fact that it is constantly exposed to innumerable pathogens. The chemical anti-bio agents exploited against these pathogens were harmful to environment and human health as well. So the only alternative way is to grow disease resistant varieties of crops by introducing resistant (R) genes. However, new pathogenic races evolve constantly and are notorious for their ability to withstand race specific resistance mediated by R-genes . Plants deploy robust, broad-spectrum and durable resistance mechanisms called nonhost resistance (NHR) against most pathogenic organisms. Such disease resistance mechanisms are nonspecific and effective against all nonhost or non-adaptive pathogens. The NHR defence response includes production of phytoalexins and other antimicrobial compounds, hypersensitive response by rapid localized cell death, deposition of callose and expression of pathogenesis related genes at the site of infection that restricts further growth of pathogen. Although NHR has immense potential to improve crop production in agriculture, very little is known about the mechanism of NHR and its genetic pathways at molecular level. Detail knowledge about the NHR genes from a nonhost plant and engineering the NHR gene into the host plant will be helpful in making broad-spectrum and durable disease resistant crops. In this mini review, we report the list of NHR genes and their function against various phytopathogens. We further report a method to identify or map putative NHR gene/s in Arabidopsis against soybean pathogen Phytophthora sojae nonhost with a goal to improve disease resistance in crop species.