The Rice-Xoc Arms Race: Molecular Mechanisms and Genomic Strategies Against Bacterial Leaf Streak

Rice is a staple crop, serving as the primary food source for over half of the world's population, but its productivity is limited by several diseases, necessitating the development of sustainable, resistant varieties. However, breeding for pathogen-resistant rice varieties is challenged by the quantitative nature of resistance, and the accelerated evolution of pathogens under climate change. The economically important bacterial rice pathogens, bacterial leaf blight and bacterial leaf streak, are caused by different pathovars of the same species (Xanthomonas oryzae) which share significant genomic similarities, yet they have different infection mechanisms and cause distinct symptoms. As bacterial leaf streak resistance is largely governed by quantitative trait loci (QTLs), this review provides an updated synthesis of QTLs and explores the molecular landscape of Transcription Activator-Like Effectors (TALEs)-host interactions, specifically how bacteria recruits host susceptibility (S) genes to facilitate infection, virulence targets in host gene promoters, and defense-related genes that can facilitate the production of rice varieties with durable resistance to bacterial leaf streak. In addition, this review highlights the progress in bacterial leaf streak resistance breeding programs through the application of marker-assisted selection and the application of gene-editing tools. Collectively, it concludes that future breeding programs will integrate advanced genetic and computational tools to develop rice varieties with durable and broad-spectrum resistance to bacterial leaf streak and other pathogens.