Control of Colletotrichum acutatum and Colletotrichum gloeosporioides by ethanolic extract of the macroalgae Osmundaria obtusiloba

• Grant number: 19/22051-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2020
• End date: December 31, 2021
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Maria Candida de Godoy Gasparoto
• Grantee: Thais Vianna Brito
• Host Institution: Universidade Estadual Paulista (UNESP). Campus de Registro. Registro , SP, Brazil

Abstract

The citrus represents a large group of plants of the genus Citrus, which comprise some of the most important cultivated species of Brazilian agricultural production. Despite their high productive potential on national lands, a lot of diseases can affect the production of citrus plants, resulting in a significant decrease in commercial orchards. The post-bloom fruit drop of citrus, caused by the fungi Colletotrichum acutatum and Colletotrichum gloeosporioides, is one of the diseases that cause damages to the national citrus production, and under favorable environmental conditions, losses can reach 80%. Few fungicides are registered to control this disease and, even with a low incidence of rain during the flowering period, citrus growers in the most disease-affected regions prevent epidemics using chemical control. Furthermore, there are no reports of biological and/or alternative control of this disease in commercial orchards. Preliminary works at UNESP - Câmpus Experimental de Registro - have shown that some algae extracts have beneficial effects on inhibition of mycelial growth and germination of the causal agents of citrus post-bloom fruit drop. Ethanolic extract of the macroalgae Osmundaria obtusiloba showed inhibition of 75.3% in conidial germination of C. acutatum when applied at the concentration of 1000 µg.mL-1. To inhibit 100% of mycelial growth of C. gloeosporioides, it was necessary a concentration of 10000 µg.mL-1 of the same extract. Thus, further investigation into the antifungal potential of this and other extracts of the same macroalgae should be stimulated. The objective of this work is to evaluate the mycelial growth, sporulation and conidial germination of Colletotrichum acutatum and Colletotrichum gloeosporioides in different concentrations of ethanolic extract of Osmundaria obtusiloba seaweed. We will also evaluate the effect of the ethanolic extract on appressorial development, and secondary conidiation. (AU)