Biotechnological approaches to the control of citrus huanglongbing using transgenic plants

Abstract

Huanglongbing (HLB) is the major threat to the citriculture worldwide. The fast and efficient dissemination of the HLB associated bacteria, Candidatus Liberibacter spp., by its psyllid vector Diaphorina citri and the absence of genetic resistance in citrus, are major factors accounting for disease severity. The development of varieties with good agronomic performance and resistance to disease has been an efficient and environmentally sustainable way to control diseases in different crops. However, reproductive and genetic constraints of citrus make the classical breeding a long process, exacerbated with lack of resistance to Liberibacters and to the insect vector. Biotechnological approaches have a valuable potential to solve these problems. The production of transgenic citrus resistant to HLB, therefore, has been anxiously expected as an important alternative to the current strategies that have been applied to manage the disease. This potential outcome might strengthen the Brazilian citriculture in technical and economic aspects, keeping Brazil as the leading country in orange juice production and commercialization. To reach such goals, we propose in this project: i) to produce transgenic sweet orange expressing prophage genes from Ca. Liberibacter sp. to confer resistance to HLB; ii) to identify D. citri genes related to insect growth and development as well as genes involved in Liberibacter acquisition and infection; iii) to develop a transient RNA interference system in planta with D. citri genes and test its efficacy in transgenic citrus plants; iv) to develop a regeneration and genetic transformation system on Murraya sp. to incorporate resistance to D. citri. These subprojects are related to each other and have as a common theme the genetic control of the main citrus disease in Brazil and worldwide. (AU)