Banca de QUALIFICAÇÃO: LAURA NOBREGA MEIRELLES

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : LAURA NOBREGA MEIRELLES
DATE: 25/09/2025
TIME: 13:00
LOCAL: UFRRJ, IV, DPA, Sala 14
TITLE:

Development of microparticles with Metarhizium conidia: characterization, stability and application in Rhipicephalus microplus control

KEY WORDS:

entomopathogenic fungi, ionic gelation, cattle tick

PAGES: 40
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUBÁREA: Medicina Veterinária Preventiva
SPECIALTY: Doenças Parasitárias de Animais
SUMMARY:

Entomopathogenic fungi are a sustainable alternative for the biological control of Rhipicephalus microplus, especially due to the resistance of ticks to chemical acaricides. However, the climate crisis emphasises the importance of developing formulations, since adverse environmental factors can compromise their viability. Ionic gelation applied to propagule encapsulation allows polymers and adjuvants to be combined to protect the fungus and improve its shelf life. This study aimed to develop microparticles containing Metarhizium anisopliae s.l. CG 148 conidia encapsulated with different combinations of sodium alginate (A), pectin (P), chitin (Q) and glycerol (G). The encapsulation efficiency and the influence of chitin addition on conidia production were investigated, and the particles were analyzed for size distribution, morphology, UV-B tolerance, thermotolerance, and efficacy in controlling engorged females of R. microplus in the laboratory. Fungal microparticles A, AQ, AP, APQ, AG, AGQ, APG, and APGQ were prepared. Process efficiency was assessed by quantifying and verifying the viability of the encapsulated conidia. To investigate the effect of chitin on propagule production, the sporulated conidia of the microparticles incubated in culture medium were quantified. Formulations containing chitin were selected for the following experiments. Microparticle characterisation included the determination of size distribution using ImageJ software and analysis of external morphology through observations under a stereomicroscope and scanning electron microscopy. To assess UV-B tolerance, microparticles and suspensions of non-encapsulated conidia (NEC) were exposed to a total dose of 6.0 kJ m-2, while for thermotolerance they were exposed to 45 °C in a water bath for 4 hours. Finally, the biological parameters and survival of engorged females exposed to 30 mg of microparticles were analysed. Encapsulation reduced the initial concentration of conidia by an average of 2.5× and did not affect their viability. The chitin incorporated into the formulations increased conidia production by the microparticles.The particles were spherical and subspherical in shape with a more homogeneous (APQ and APGQ) or heterogeneous (AQ and AGQ) surface. The average diameter of the AQ, APQ, AGQ, and APGQ microparticles was 1338, 1459, 1244, and 1367 µm, respectively. Exposure to UV-B and heat reduced NEC germination compared to encapsulated conidia. Microparticles reduced biological parameters and tick survival compared to control groups (Tween and microparticles without fungus). However, treatments with microparticles produced similar results to those obtained with NEC, except for the survival of ticks exposed to the AQ and APQ formulations. Thus, the incorporation of chitin into the formulations acted as a propagule multiplier, while the formulations increased the tolerance of M. anisopliae s.l. CG 148 to radiation and heat and were effective in controlling R. microplus. These findings reinforce the potential of fungal microparticles as an innovative approach to controlling this tick, adding technological value to a final product that offers practical advantages for field use, such as easily application and greater stability.

COMMITTEE MEMBERS:
Interna - ***.326.816-** - MARIANA GUEDES CAMARGO - UFRRJ
Interno - 1296670 - WENDELL MARCELO DE SOUZA PERINOTTO
Externa ao Programa - 387922 - VANIA RITA ELIAS PINHEIRO BITTENCOURT - UFRRJExterno à Instituição - JHONES LUIZ DE OLIVEIRA
Externa à Instituição - VALESCA HENRIQUE LIMA - UFG