It is concluded 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.
Abstract
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.
Bacterial leaf blight (BLB) is a major constraint to rice production worldwide due to its rapid spread and the high genetic variability of its causal agent, Xanthomonas oryzae pv. oryzae. The pathogen primarily enters rice plants through natural openings such as hydathodes or through wounds, subsequently colonising the xylem vessels and spreading systemically within the vascular system, leading to characteristic disease symptoms. The ability of the bacterium to infect the host depends on several virulence factors, including biofilm formation, exopolysaccharide production, quorum sensing and the secretion of effector proteins into the host. These proteins, known as transcription activator-like (TAL) effectors, play a crucial role in pathogenesis by modulating host gene expression to facilitate infection. Rice plants counter BLB through multiple defence mechanisms, including the formation of structural barriers, production of antimicrobial compounds andmodulation of gene expression. Some rice cultivars exhibit greater resistance to BLB than others, which is largely determined by genetic factors. This review examines the defence strategies of rice and provides key insights into host-pathogen interactions that inform the development of durable resistance and improved disease management strategies. Understanding these interactions provides a foundation for integrating molecular breeding with sustainable agricultural practices to mitigate yield losses caused by BLB.
M. Syed, N. Rajinimala, M. Theradimani et al.· Plant Science Today· 0 citations
More than 50% of the world's population is reliant on rice (Oryza sativa L.) as their main dietary source, but harmful fungal diseases are a constant threat to its production. Each year, significant yield losses occur due to pathogens like Rhizoctonia solani (sheath blight), Magnaporthe oryzae (rice blast) and Ustilaginoidea virens (false smut). The frequent use of chemical fungicides used to treat these diseases have led to the development of tolerance pathogen stress and serious environmental issues. A viable and long-term alternative is biological control, which makes use of more beneficial microorganisms called biocontrol agents (BCAs). This review summarizes recent findings on the use and actual mechanisms of BCAs against the primary rice fungal pathogens. We analyze the variety of microbial antagonists, which comprise the fungal and bacterial genera Trichoderma and Bacillus, Pseudomonas, and Streptomyces and other endophytic fungi. These BCAs have a variety of functional mechanisms, include competition for nutrients and space, direct hostility through mycoparasitism, and antibiosis, as well as indirect mechanisms such as the induction of systemic resistance (ISR) in the host plant and plant growth promotion (PGP).We discuss a variety of methods of application, like as foliar sprays, soil inoculation, and seed dressing, and focus on the significance of developing stable and efficient formulations. In order to improve the efficacy and reliability of biocontrol in rice agroecosystems, we deal with the issues preventing the broad use of BCAs, such as uneven field performance and regulatory barriers, and we suggest future research possibilities, such as the development of synthetic microbial consortia and the application of multi-omics technologies.
Whether, and where, genomic technologies have altered breeding outcomes rather than merely accelerating gene discovery is examined, and the available evidence indicates that genomic resources have substantially improved the resolution of resistance discovery and the precision of marker-assisted introgression, but have not yet demonstrably improved durability.
Vishal Singh, Mitali Tiwari, Diksha Kushwaha et al.· Uttar Pradesh Journal of Zoo...· 0 citations