Rice resistance genes to leaf blight caused by Xanthomonas oryzae pv. Oryzae (review)

Abstract

Rice is the most important food crop for the world population and has been cultivated for more than 10 centuries. It is affected by various viral, fungal and bacterial diseases, the most harmful of which is leaf blight, which is caused by the bacterium Xanthomonas oryzae pv. oryzae (Xoo). The most effective way to combat leaf blight is to use resistant varieties together with good agro-technical methods. In recent years, there has been carried out an extensive genetic and genomic study to identify the molecular mechanism of rice reaction to Xoo. As a result of long-term study by the Southeast Asian farmers there were identified 42 different leaf blight resistance genes, 9 of which were isolated and cloned. Currently, complete genome sequences are available for two different rice subspecies ‘Japonica’ and ‘Indica’ and three different races of the leaf blight pathogen. Therefore, there can be estimated an interaction between rice and Xoo, which will allow establishing host responses such as innate immunity and R gene-mediated immunity. Functional analysis of resistance genes may provide clues to the development of a broad spectrum and long-term resistance to leaf blight. There has been characterized a number of resistance (R) genes and related avirulence genes and effector virulence genes. This review, based on published works has presented the latest advances in the study of correlation between rice and the pathogen through R genes and their products. There has been also discussed breeding strategies in order to develop varieties with long-term and broad resistance to Xanthomonas oryzae.