Citrus tristeza virus: A century-long challenge for the world's citrus industries

Citrus tristeza virus (CTV) is a causal agent of diseases that have challenged the global citrus production for more than a century. The disease named ‘tristeza’, which means ‘sadness’ in Portuguese and Spanish, has spread by aphids and vegetative propagation, resulting in costly pandemics that reshaped the world citrus production by forcing the adaption of disease-tolerant rootstocks. Furthermore, management of the second major CTV-induced disease, stem pitting, became a unique example of the use of cross-protection on a large nationwide scale, allowing many citrus growing regions to control the disease that could not be managed through horticultural practices. The information gathered in this review commemorates a hundred years of research on the virus and the respective diseases, which began with classical horticultural approaches and advanced toward the cutting-edge molecular biology studies. In this regard, it is proper to mention that CTV research greatly benefited from close international collaboration between research institutions and scientists from the affected and nonaffected citrus areas. Moreover, despite the considerable initial losses caused by tristeza, the world's fresh fruit and juice concentrate citrus industries reemerged as highly productive following the research advancements, a situation that changed throughout Florida and Brazil in the past two decades or so with the outbreak of the devastating citrus greening (Huanglongbing) bacterial disease. This review encompasses past and recent advances in the CTV research positioning the citrus-CTV pathosystem as a pivotal model system for investigating virus interactions with perennial woody hosts. The review will also serve as an updated version of the respective section on CTV in the Description of Plant Viruses that the Association of Applied Biologists manages. We dedicated this review to the 85th Birthday celebration of Prof. Moshe Bar-Joseph, a world-renowned plant pathologist whose half-a-century-long career devoted to citrus diseases yielded many important, pioneering discoveries on CTV and other closteroviruses. Many of those are highlighted in this review. Prof. Bar-Joseph retired from the Volcani Center, Agricultural Research Organization in Israel several years ago, yet he continues to be actively engaged in research and provides his expertise to citrus pathologists around the world in the present days.