Study of Lasiodiplodia theobromae as pathogen in Khaya ivorensis and search for secondary metabolites for the control of the fungus

• Grant number: 11/19148-2
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: January 01, 2012
• End date: December 31, 2014
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Organic Chemistry
• Principal Investigator: Maria Fátima das Graças Fernandes da Silva
• Grantee: Leonardo Toffano
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 08/57859-5 - Biorrational control of insect pests, AP.TEM

Abstract

The Brazilian mahogany (Swietenia macrophylla King) is being replaced by African mahogany Khaya ivorensis, K. senegalensis, K. nyasica and K. antotheca due to its susceptibility to Hypsiphyla grandella, the major pest of hardwood in Brazil. These African species show great resistance to H. grandella when introduced in tropical America. But after its introduction in Brazil, the African mahogany has been found with diseases caused by fungi. Molecular studies developed by the Natural Products Group UFSCar led him to identify two isolates of K. ivorensis as Botryosphaeria rhodina and its anamorph Lasiodiplodia theobromae. Genetic data were deposited in the "GenBank" (ITS-1 ITS-2, GenBank EU276018). In studies conducted in April 2009 the fungus B. rhodina from the plant K. ivorensis, developed in PDA medium and inoculated in the same healthy plants. Three inoculations were made at each plant. After seven months (November 2009) experiment was assumed that the first signs of the disease had been found. However, in August 2010 on a visit to the experiment station, it was found that the signals evolve in no reproduction of symptoms, and can only check injuries (cuts) caused by the tools of inoculation. Therefore, the steps of Koch's postulates have not been completed. Unfortunately, the doctoral student has not done a good survey of the literature on information which anamorph of the fungus alone would be responsible for the disease cancker in other plants studied so far. It was easier to grow large-scale B. rhodina in the lab, and wrongly concluding that this is the anamorph pathogenic. The literature shows that the fungus L. theobromae is the causal agent of several diseases in Brazilian agriculture, including cancker. Unfortunately, this also showed the absence of pesticides registered in Brazil to control the fungus. Therefore, studies chemical and biological urges of L. theobromae, which may provide possible strategies for controlling cancker Mahogany, which has spread through various regions of Brazil, like Bahia and São Paulo. A study conducted at the Natural Products Laboratory of UFSCar, K. ivorensis presenting symptoms of cancer and healthy were collected on the same day and worked on simultaneously. This study led to the isolation of these compounds in both plants. The striking difference between them was the presence of limonoid methyl angolensato as traces in the stem of the plant is a large and healthy that they had injuries. The objective of this project is to study chemical and biological interactions involving small molecules in host-L. theobromae, to establish strategies to control cancker Mahogany. For this the following steps will be developed: - Apply the Koch's postulates in the interaction between Lasiodiplodia theobromae and Khaya ivorensis; - Develop and implement methodologies to assess the effect of methyl angolensato on the development of L. theobromae - Evaluate the effect of compounds isolated by the group Natural Products UFSCar in inhibiting the development "in vitro" of L. theobromae, and - Identification and characterization of fungi isolated from plants of K. ivorensis via DNA analysis.