Banca de DEFESA: MARIA HELENA DIÓGENES COSTA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : MARIA HELENA DIÓGENES COSTA
DATA : 27/06/2025
HORA: 13:00
LOCAL: A denifir
TÍTULO:

DYNAMICS OF Fusarium INFECTION IN DIFFERENT PARTS OF MELON DURING THE VEGETATIVE CYCLE: IMPLICATIONS FOR DISEASE MANAGEMENT AND SIRNAS COMPLEXED WITH CHITOSAN NANOPARTICLES PROVIDE LONG-LASTING PROTECTION AGAINST POTATO VIRUS Y INFECTION

PALAVRAS-CHAVES:

Cucumis melo L., Fusarium rot, infection, RNA Interference, Nanocarrier, Viral Disease Suppression

PÁGINAS: 58
RESUMO:

Melon is a crop of great global importance, and Brazil is one of the biggest melon producers. The northeast of Brazil is the country's main melon-producing region, with the states of Ceará (CE) and Rio Grande do Norte (RN) responsible for more than 77% of all national production. This study aimed to clarify the dynamics of Fusarium infection in Cucumis melo. In 2022, two field experiments were carried out where different tissues of melon plants were evaluated at four different times, being E1: day of seedling transplanting (root, stem, cotyledon); E2: 14 days after seedling transplanting (root, stem, branch, leaf); E3 and E4: 45 and 60 days after seedling transplanting (root, stem, branch, leaf, and fruit). Additionally, flowers were isolated 28 days after transplanting, and fruits were isolated 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. 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. 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. falciforme, F. pseudensiforme and F. silvicola (F. solani species complex - FSSC). 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, affecting all parts of the plant, with the roots serving as the main entry point for the fungus. These findings emphasize the need for a comprehensive disease management plan focusing on pathogen-free substrates, soil inoculum reduction, and flower protection to control Fusarium infections in Brazilian melon production. Separately, 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 (one of the RNAi inducers) to plants is challenging, and chitosan nanocarriers stand out as a promising solution. We hypothesized that siRNAs complexed with chitosan nanoparticles applied to plants will suppress PVY infections. To test our working hypothesis, we designed siRNAs from the P1 cistron of the PVY genome, complexed 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 PVY inoculations were performed 10 days later. We evaluated disease severity and ran RT-qPCR (to measure viral transcripts) 14 days after PVY inoculations. We observed that when plants were treated with siRNAs and challenged with PVY on the same day, the disease was suppressed regardless of whether the siRNAs were complexed with chitosan in nanocarriers or not. However, when plants were challenged with PVY 10 days after siRNA applications, complexed siRNAs suppressed the virus more efficiently than non-complexed siRNAs. These results suggest that siRNA complexed with chitosan nanocarriers can promote long-lasting protection against target viruses, a promising tool to manage plant viral infection.

MEMBROS DA BANCA:
Externa à Instituição - ANDREIA MITSA PAIVA NEGREIROS - UFERSA
Externo à Instituição - DARLAN FERREIRA BORGES - PESQUISADOR
Externo à Instituição - HAILSON ALVES FERREIRA PRESTON - UFRN
Interna - 2578315 - JAILMA SUERDA SILVA DE LIMA
Presidente - 1544411 - MARCIA MICHELLE DE QUEIROZ AMBROSIO
Interno - ***.076.546-** - WASHINGTON LUÍS DA SILVA - CAES