Bioprospecting microorganisms with potential to mitigate Candidatus Liberibacter asiaticus and HLB

• Grant number: 24/22941-6
• Support Opportunities: Scholarships in Brazil - Master
• Start date: July 01, 2025
• End date: April 30, 2026
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Helvecio Della Coletta Filho
• Grantee: Alessia Zincone Volponi
• Host Institution: Instituto Agronômico (IAC). Agência Paulista de Tecnologia dos Agronegócios (APTA). Secretaria de Agricultura e Abastecimento (São Paulo - Estado). Campinas , SP, Brazil
• Associated research grant: 20/14584-8 - Synthetic communities of the citrus rhizosphere microbiota seeking benefits for plant development and resistance to stress, AP.TEM

Abstract

Currently, among the main citrus diseases occurring in the State of São Paulo, Huanglongbing (HLB), caused by the bacterium Candidatus Liberibacter asiaticus (CLas), is the most problematic for citrus cultivation. To date, it has not been possible to cultivate CLas under axenic conditions, i.e., outside its hosts (plant and Diaphorina citri), which has hindered the study of this pathogen. Microorganisms with genetic proximity to CLas and capable of growing in culture media, such as Sinorhizobium meliloti(Sme) and Liberibacter crescens, have been used in in vitro studies to identify antimicrobial compounds or microorganisms antagonistic to CLas. However, these are merely model microorganisms. For efficient and accurate screening, it is necessary to develop rapid in vitro screening methods, as well as in situ methods to evaluate the behavior of potential antagonists directly against CLas.For in vitro assays or the development of tests, the bacterium Sinorhizobium meliloti (Sme) can be used in systems to identify antimicrobials against CLas. The "hairy roots" system can provide a highthroughput analysis methodology for in situ tests, enabling the selection of potential antagonistic molecules against CLas. The challenges related to the efficiency and sustainability of controlling these two pathogens highlight the need for biotechnological solutions, such as biological control using microorganisms. Therefore, this work aims to select and test bacterial genera previously described as antagonistic to plant pathogens against Candidatus Liberibacter asiaticus. The specific objectives are: i. to test in vitro antagonistic bacteria with potential for CLas control; ii. to develop an in situ system for antagonism testing against CLas.