N-acetylcysteine in infected citrus plants by Candidatus Liberibacter asiaticus: possible effects on the pathogen and host

Abstract

The citrus industry stands out for its great importance in the São Paulo and Brazilian agribusiness, presented as the Brazilian agricultural commodity with more hegemony in foreign markets. Major producing areas of citrus in the world such as Asia, the Americas and Africa are facing with a major pest problem, the HuangLongBing (HLB), also known as greening. In Asia and America the HLB is predominantly caused by bacterial species Candidatus Liberibacter asiaticus (CLas), which colonizes the phloem of the host plant causing severe symptoms in leaves and fruits, affecting plant productivity and fruit quality for both processing fruit industry and for fresh consumption. The recommended handling and technically proven for this disease is founded on the principles of exclusion, eradication and protection. However, although still being mandatory, the eradication of plants with HLB has increasingly been neglected, passing to live with the disease, delaying the lifetime of the plant. Different types of molecules have been used for the management of fitopathogens, taking direct action on the pathogen or as plant resistance induction potentiator. As an example, the use of antioxidant molecules such as N-acetylcysteine which showed promising results against Xylella fastidiosa, which causes citrus variegated chlorosis (CVC) and Xanthomonas citri, which causes citrus canker. Antibiotics such as penicillin, tetracycline and streptomycin have been tested against CLas in vitro tests, in vivo and some are already used in the field. This project aims to evaluate the effect of these compounds in sweet orange infected with CLAS, in order to verify the change in bacterial concentration, the activity of enzymes in response to oxidative stress caused by bacterial infection and the expression of genes related to starch accumulation, a consequence of infection by CLas. (AU)