Leaf‐disc grafting for the transmission of Candidatus Liberibacter asiaticus in citrus (Citrus sinensis; Rutaceae) seedlings

Abstract

Premise of the study:The search for resistance/tolerance to the devastating citrus huanglongbing disease (syn. HLB or citrus greening) is generating an increasing number of new plants of diverse genetic makeup. As the increasing number of new plants require more space, resources, and time, the need for faster and more efficient HLB screening tests becomes crucial.Methods and Results:The leaf-disc grafting system described here consists in replacing a disc of leaf tissue with a similar disc from an infected plant. This can be performed in young seedlings not yet big enough to endure other types of grafting. Graft success and infection rates average approximately 80%.Conclusions:We describe the successful adaptation of leaf-disc grafting as a powerful screening tool for HLB. The system requires minimal plant material and can be performed in seedlings at a very young age with increased efficiency in terms of time, space, and resources.

Comparative Leaf Volatile Profiles of Two Contrasting Mandarin Cultivars against Candidatus Liberibacter asiaticus Infection Illustrate Huanglongbing Tolerance Mechanisms

“…Under natural field conditions, Ca Las is transmitted from one host plant to another by a sap-sucking insect, the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera; Psyllidae) or leaf tissue …”

“…1 CaLas can also be transmitted through artificial graft inoculation using diseased budwood 1 or leaf tissue. 6 HLB-affected citrus plants often develop complex symptoms, including typical blotchy mottled leaves, twig dieback, deformed fruits with aborted seeds, inversive coloration (orange at the stem end, and green at the blossom end, thus the common name "citrus greening disease"), premature fruit drop, root loss, tree decline, and in some severe cases eventually tree death. 1,7 No effective cure is available currently for HLB-affected citrus plants.…”