Banca de QUALIFICAÇÃO: ALLAN FELIPE MARCIANO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : ALLAN FELIPE MARCIANO
DATE: 30/06/2020
TIME: 13:00
LOCAL: On Line RNP
TITLE:

Soil application of Metarhizium spp.: Isolates selections, antimicrobial action, and efficacy for the control of Rhipicephalus microplus

KEY WORDS:

Soil application, biological control, cattle tick, entomopathogenic fungus, fungal exudate.

PAGES: 121
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUBÁREA: Medicina Veterinária Preventiva
SPECIALTY: Doenças Parasitárias de Animais
SUMMARY:

The fungal genus Metarhizium is commonly found in soil and plant roots, and it is one of the main agents used in the biocontrol of agricultural pests. In this context, pasture is a favorable environment for the development of this microorganism, where the plant's rhizosphere and the presence of hosts such as the tick Rhipicephalus microplus make the best ecological niche for the fungus. However, biotic and abiotic factors interfere on its persistence in the environment; it is essential to select fungal isolates, consider ecological interactions with other microorganisms, and formulate them. Based on this, the present study addresses some tests, which consider the applicability of the genus Metarhizium spp. in the control of pests that inhabit the soil. Therefore, the following were evaluated: heat tolerance and the ability of different isolates of the fungus to colonize tissues of the Vigna radiata plant; the antimicrobial and acaricidal effect of fungal exudate; and the effectiveness of granular formulations of M. robertsii microesclerotia and blastospores to control cattle ticks. In the heat tolerance test, conidial suspensions of the fungus were exposed to 25 ° C, 40 ° C and 45 ° C, for 2h, 4h, 8h and 12h, and the germination was evaluated after incubation for 48h at 28 ± 1 ° C, based on that, heat-tolerant isolates were selected. For the study of endophytic colonization, seeds, root, stem, and leaf of V. radiata were treated with fungus suspensions, and the colonization of the plant tissues by different isolates was evaluated. To assess the effect of fungal exudate on ticks and bacteria, drops of this metabolite secreted by the colonies of Metarhizium spp. were collected. Then, from the disk diffusion test, the effect on strains of two bacteria isolated from the soil and on resistant and sensitive strains of Staphylococcus and Escherichia coli was evaluated. For the action on ticks, the fungal exudate was inoculated in tick females and the biological parameters, mortality, and immune response of the arthropod were evaluated. Finally, for the test with microsclerotia and blastospore granular formulations, the soil of pots containing Brachiaria decumbens were treated or not with granular formulations. Subsequently, females of R. microplus were exposed to this environment and mortality, the number of larvae obtained in each group, as well as the persistence of the fungus in the soil were evaluated. As regards to the results, in the heat tolerance test, all Metarhizium spp. isolates tested germinated well after 12h at 40 ° C and were considered good isolates, those that did not suffer drastic variation in germination over the time of exposure. When evaluated the ability to colonize V. radiata, all tested isolates were able to colonize roots, stems, and leaves, with variation in the colonization of different tissues. The fungal exudate was also able to inhibit the growth of the resistant and sensitive strains of Staphylococcus spp., and it affected more the strains of bacteria isolated from the soil than the others. The exudate also directly affected engorged R. microplus females, reducing the cellular immune response, causing death, and decreased egg production. The treatment with different concentrations of granular formulations of M. robertsii proved to be effective in controlling the cattle tick under the conditions tested. This study provides data about the application of Metarhizium spp. in the soil and contributes to future research, showing the bioprospecting of this microorganism.

 

BANKING MEMBERS:
Presidente - 387922 - VANIA RITA ELIAS PINHEIRO BITTENCOURT
Interna - 2860277 - ISABELE DA COSTA ANGELO
Externo à Instituição - EVERTON KORT KAMP - UFG
Externa à Instituição - MARIANA GUEDES CAMARGO - UFRRJ
Externa à Instituição - SIMONE QUINELATO BEZERRA - FIOCRUZ