Banca de QUALIFICAÇÃO: MARIA HELENA DIÓGENES COSTA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : MARIA HELENA DIÓGENES COSTA
DATA : 24/04/2025
HORA: 09:30
LOCAL: Google Meet (online)
TÍTULO:

Título 1: ROUTE OF INFECTION OF FUSARIUM SPP. IN MELON

Título 2: ENCAPSULATING SIRNAS IN CHITOSAN NANOPARTICLES TO SUPPRESS POTATO VIRUS Y INFECTION

PALAVRAS-CHAVES:

Palavaras-chave 1: Post-harvest, Cucumis melo L., Fusarium spp, route of infection

Palavras-chave 2: RNA Interference, Nanoparticles, Viral Disease Suppression

PÁGINAS: 58
RESUMO:

Resumo 1: This study aimed to clarify the route of Fusarium infection in Cucumis melo. In 2022, two field experiments were carried out. Different tissues of melon plants were evaluated at four different times, being E1: day of seedling planting (root, stem, cotyledon); E2: 14 days after seedling planting (root, stem, branch, leaf); E3 and E4, 45 and 60 days after seedling planting (root, stem, branch, leaf, and fruit). In addition, flowers were isolated 28 days after transplanting and fruits 30 days after harvest. Seeds and substrates used for seedling production were also analyzed. Fusarium was isolated from all plant tissues analyzed. From the fragments of plant tissues and substrate analyzed, 197 Fusarium colonies were isolated, with 23 isolates selected for molecular identification. Fourteen species of Fusarium were identified: F. caatingaense, F. ipomoeae, F. longifundum, F. mucidum, F. sulawesiense (F. incarnatum-equiseti species complex -FIESC): F. spinosum (F. chlamydosporum species complex - FCSC); F. delphinoides (F. dimerum species complex - FDSC); F. verticillioides (F. Fujikuroi species complex - FFSC); F. contaminatum, F. kalimantanense, F. triseptatum (F. oxysporum species complex - FOSC); F. falsiforme, F. pseudensiforme and F. silvicola (F. solani species complex - FSSC). In most of the periods analyzed, we found the largest number of fragments with Fusarium in the roots, as well as the largest number of species. No Fusarium species were found in the seeds analyzed. All molecularly identified Fusarium species were pathogenic to fruits and seedlings., with the species belonging to the FSSC complex being the most aggressive. We conclude that Fusarium has multiple infection routes in melons, including roots, stems, branches, leaves, flowers, and fruits, with the roots serving as the main entry point for the fungus.


Resumo 2: Potato virus Y (PVY) is a significant threat to potato crops, with no virucidal solutions available. RNA interference (RNAi) emerges as a promising tool for plant virus control. However, effective delivery of siRNAs (a type of RNAi inducer) to plants is challenging, and chitosan nanocarriers stand out as a promising solution. We hypothesized that siRNAs encapsulated with chitosan nanoparticles applied to plants will triger RNAi and suppress PVY infections. To test our working hypothesis, we designed siRNAs, from the P1 cistron of the PVY genome, encapsulated them with chitosan nanoparticles, applied the nanocomplex to tobacco plants, and challenged the treated plants with PVY at two distinct times. Experiment 1: the application of the treatments and PVY inoculations were performed on the same day; Experiment 2: The treatments were applied and 10 days later PVY inoculations were performed. We evaluated disease severity and run RT-qPCR (to measure viral transcripts) at 14 days after PVY inoculations. We observed that when plants are treated with siRNAs and challenged with PVY on the same day, the disease is suppressed regardless of whether the siRNAs are encapsulated in nanocarriers or not. However, when plants are challenged with PVY 10 days after siRNA applications, encapsulated siRNAs suppressed the virus more efficiently than non-encapsulated siRNAs. These results suggest that siRNA encapsulated in chitosan nanocarriers can promote long-lasting protection against target viruses, a promising tool to manage plant viral infection.

MEMBROS DA BANCA:
Externo à Instituição - FRANCISCO ROMÁRIO ANDRADE FIGUEIREDO
Interna - 2578315 - JAILMA SUERDA SILVA DE LIMA
Presidente - 1544411 - MARCIA MICHELLE DE QUEIROZ AMBROSIO
Interno - 1445570 - RUI SALES JUNIOR
Interno - ***.076.546-** - WASHINGTON LUÍS DA SILVA - CAES