Banca de DEFESA: MARCELA DE SOUZA ALVES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : MARCELA DE SOUZA ALVES
DATE: 21/12/2021
TIME: 13:30
LOCAL: PPGQ/UFRRJ - Link da videochamada: meet.google.com/uos-kjny-vvx
TITLE:

Lemongrass essential oil: an agroecological approach to protect stored grains and seeds against cowpea weevil

KEY WORDS:

Essential oil, Cymbopogon citratus, Callosobruchus maculatus, biological activity.

PAGES: 116
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUMMARY:

The main cause of postharvest economic losses of cowpea (Vigna unguiculata (L.) Walp) is due to infestation by the weevil, the Callosobruchus maculatus insect pest. Numerous studies point to essential oils as promising in the insect pest control, including lemongrass essential oil, which inhibits the reproductive cycle and aspects of the weevil metabolism, indicating the biotechnological potential of this bioactive.In this context, one of the objectives of this work was to evaluate the fumigant effect of lemongrass essential and the major substance (citral) on the reproductive cycle and the likely metabolic targets of these bioactives. For this purpose, an experimental design was developed that allowed to evaluate the essential oil and citral effect, in different concentrations, on mortality, egg laying and the new adult’s emergence, as well as to evaluate the metabolic profile and genes expression of enzymes involved in the energy metabolism of insects subjected to essential oil in a time and concentration of low lethality. As an unfolding of the essential oil's insecticidal activity, the other objective was to evaluate a possible agroecological strategy for the cowpea seeds protection. For this purpose, an experimental design was proposed that would enable the evaluation of how long the cowpea seeds coated with lemongrass essential oil would be protected against weevil. Furthermore, the essential oil toxic effect on opportunistic fungi, the seed viability based on a germination test and the toxicity of lemongrass essential oil against Saccharomyces cerevisiae yeast cells were evaluated. To support the studies, the lemongrass essential oil chemical characterization was previously performed, and the seeds coated with the same essential oil were periodically washed for up to 180 days of storage, to assess the presence of essential oil substances in the seeds (residue).Among the main results, there was a low toxic effect by fumigation of the essential oil on insect mortality, but high inhibition of egg laying and the new adult’s emergence. A predominance of energy reserves, based mainly on sugars (trehalose and glucose) and amino acids (proline and alanine), in control insects was observed, although, in the insects subjected to the fumigating effect of essential oil, were observed increased levels of glycerol and decreased relative expression of hexokinase, lactate dehydrogenase and malate dehydrogenase.It was found that cowpea seeds coated with lemongrass essential oil did have citral residues on their surface and provide relative protection against weevils for up to 90 days of storage. A toxic effect of the essential oil on the growth of Fusarium spp., Colletotrichum spp., Aspergillus spp., Penicillium spp and on S. cerevisiae yeast cells was observed. There was no effect of the essential oil on the cowpea seeds germination. Based on the tests carried out, it is concluded that the lemongrass essential oil has the potential to develop strategies to protect grains and seeds in replacement of traditional control, mainly in service to the organic seed production sector.

BANKING MEMBERS:
Presidente - 2582213 - MARCO ANDRE ALVES DE SOUZA
Externo ao Programa - 1809123 - ANDRE MARQUES DOS SANTOS
Externa ao Programa - 3145590 - DANIELA COSENTINO GOMES
Externa ao Programa - 2223814 - ELEN DE LIMA AGUIAR MENEZES
Externo à Instituição - Flavio Jose da Silva Dantas - UERJ
Externo à Instituição - Petter Franco Entringer - UFRJ
Externa à Instituição - Antônia Elenir Amâncio Oliveira - UENF