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Open Access Publications from the University of California


The Journal of Citrus Pathology in an international, peer-reviewed, open access, online publication. The Journal of Citrus Pathology welcomes reports on research from all branches of pathology on all diseases of citrus and related fields. The journal accepts original contributions in basic and applied research on citrus diseases, pathogens and disease-associated agents, including graft-transmissible agents, viruses, viroids, bacteria, phytoplasmas and other wall-less bacteria, fungi, oomycetes, and nematodes as well as any agents affecting citrus biology. This on-line IOCV publication by eScholarship ensures the distribution of critical information for citrus health and hosts occasional invited autobiographies and biographies of pioneer leaders of the field of citrus pathology.

Letters to the Editor

Huanglongbing solutions and the need for anti-conventional thought

Citrus huanglongbing (HLB) has been recognized for a century yet control and management remain elusive despite over 90 years of intensive research. The bacterial pathogen is an insect endosymbiont that was most likely inadvertently introduced into citrus where it found a compatible environment for growth in citrus phloem cells and therefore jumped from the animal to plant kingdom. Because the genus citrus did not coevolve with the bacteria it has no resistance and little tolerance to it and the resulting vascular disease is severe. The winged insect vector of the bacteria, the Asian citrus psyllid (ACP), is an exotic introduced species in its own right, prolific, and difficult to control even on a regional spatial scale. The resulting disease has a long latent period prior to symptom expression and a challenging cryptic period during which detection by convention PCR and other methods can be elusive. The result is an unusually rapid increase and spread of the resulting disease. This article offers some nonconventional perspectives to examine this unusual and devastating pathosystem to stimulate though toward improved control/mitigation.


Interaction between Phytophthora nicotianae and Candidatus Liberibacter asiaticus damage to citrus fibrous roots

Huanglongbing (HLB) is associated with the phloem-limited bacterium, Candidatus Liberibacter asiaticus (Las). Phytophthora nicotianae (P.n.) causes root rot of citrus, which reduces water and nutrient uptake by citrus fibrous roots. The discovery that Las damage to fibrous roots occurs before tree canopy symptoms develop led to the prediction that Las root infection directly damages roots and may interact with soil-borne pathogens to cause further damage. Hence, comparison of root damage by Las and P.n. alone or in combination was carried out on seedlings of Cleopatra mandarin (Citrus reticulata Blanco) rootstock to evaluate the possible interaction of Las and P.n. and their relative contribution to fibrous root loss. The results demonstrated that i) roots of seedlings have a similar level of damage when inoculated with Las or P.n., and coinoculation causes comparable damage as each pathogen alone; and ii) Las infection increases and decreases P.n. infection incidence overtime without following a clear progression.