N-acetyl-cysteine (NAC): an antioxidant molecule for bacterial plant disease control

Abstract

Citriculture is the most prominent Brazilian commodity in the international market and outstands for its great importance in Brazilian agribusiness, being Brazil the world's biggest orange juice exporter, producing more than 1,000 ton of juice and generating about 230,000 jobs. The main Citriculture area in the country comprises the Citriculture belt located in São Paulo and Minas Gerais states, where it has been observed a huge decline in citrus-planted area and orange production. Many factors add up to this contraction, such as phytosanitary problems and the sector's profit decline. Among the phytosanitary problems, outstand incurable diseases that affect the orchards recurrently. Amidst them, variegated citrus chlorosis (CVC), citrus canker and HuangLongBing (HLB), also known as greening, are diseases which available tools for management have very low efficacy. For CVC the control is almost entirely based on the leafhoppers elimination with use of repeated insecticide applications. For citrus canker, the only alternative available is the elimination of symptomatic trees and the application of cupric compounds on the plants suspected of infection and for HBL the trees elimination is the only alternative. These actions have limited efficacy and present a negative impact on the profits for growers. So, we developed two new products NACsolution (for pulverization) and NACagri (a biofertilizer) to be applied in field, both based on the antioxidant, anti-adhesive and antibacterial properties of the molecule N-acetil-cysteine (NAC), a cysteine analogue widely used in human health due to its low toxicity. This compound lowers the bacteria titration in CVC-infected plants, reducing symptoms and allowing the fruit utilization for downstream juice processing, even in plants with advanced stages of infection. For citrus canker, NAC application seemed to be an alternative to block disease progression and its use in healthy plants promoted a better development of the plants. Therefore, our proposition is to keep with the NAC assessments in field with CVC and citrus canker-infected plants, as well as in field with healthy plants, eventually to present a new, more sustainable and economically viable proposition for Citriculture, with also the possibility of future application in other economically important crops. Fapesp has been financing the NAC studies in bacteria for many years and this project represents the last step in this cycle in order to transfer this technology and the intellectual production of the last years to the growers. So, at the end of this project we intend to consolidate the knowledge-to-innovation process for the benefit of the society. (AU)