Detection and Diagnosis of Bacterial Leaf Streak on Small Grain Cereals: From Laboratory to Field

Bacterial leaf streak of small-grain cereals is an economically important disease of wheat and barley crops. The disease occurs in many countries across the globe, with a particular importance in regions characterized by high precipitations or the areas where sprinkler irrigation is used. Three genetically distinct lineages of the Gram-negative bacterium Xanthomonas translucens i.e. X. translucens pv. undulosa, X. translucens pv. translucens, and X. translucens pv. cerealis are responsible for most of the bacterial leaf streak infections on wheat and barley crops. Considering the seed-borne nature of the pathogens, they are included in the A2 (high-risk) list of quarantine organisms for some European countries; hence, they are under strict quarantine control and zero tolerance. Due to the taxonomic complexities within X. translucens, the exact geographic distribution of each pathovar has not yet been determined. In this mini-review, we provide an updated overview on the detection and diagnosis of the bacterial leaf streak pathogens. First, a short history of the leaf streak pathogens is provided, followed by symptomology and host range of the causal agents. Then, the utility of conventional methods and high throughput molecular approaches in the precise detection and identification of the pathogens is explained. Finally, we highlight the role of quarantine inspections and early detection of the pathogen in combating the risk of bacterial leaf streak in the 21st century's small-grains cereals' industry.