Banca de DEFESA: MARIA EDUARDA PIMENTEL DE MELO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : MARIA EDUARDA PIMENTEL DE MELO
DATE: 28/07/2025
TIME: 09:00
LOCAL: Sala 24
TITLE:

PtxD Gene Expression in Rice (Oryza sativa L.) Confers Competitive Advantage Under Phosphite Supply: A Sustainable Approach for Weed Control.

KEY WORDS:

PtxD, Application, Control

PAGES: 78
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SUMMARY:

Climate emergency poses an increasing challenge to the sustainability of global agriculture, threatening the productivity of key crops such as rice (Oryza sativa L.). The productivity of this cereal is responsive to multiple biotic and abiotic stresses, among which nutritional deficiency and aggressive competition with weed species stand out. Phosphite, a reduced form of phosphate, has gained growing attention since the late 20th century due to its multiple beneficial roles in plant development, including its potential use as an alternative phosphorus source and its involvement in pathogen defense. However, most plants lack the metabolic capacity to directly utilize phosphite, relying instead on soil microbiota to oxidize this compound into assimilable phosphate. Consequently, biotechnology efforts have focused on developing genetically modified plants capable of metabolizing phosphite, primarily through the insertion of the PtxD gene, which encodes the enzyme responsible for its oxidation. The present study aimed to investigate the potential of foliar phosphite application technology both for mineral nutrition of transgenic plants and for selective control of weed species. To this end, plants modified to express the PtxD10.5 gene were used in experiments evaluating different phosphite doses and weed species. Initially, the weed species and phosphite dose range to be tested were established. The dose-response experiment, which applied five increasing phosphite concentrations to three weed species, revealed high sensitivity of Bidens pilosa (hairy beggarticks) and Conyza bonariensis (hairy fleabane) to doses above 500 mM, reflected in significant alterations in both phenotypic and photosynthetic parameters of these plants. In contrast, Eleusine indica (goosegrass) showed no significant response under the same conditions, indicating phosphite tolerance. In the definitive experiment, which combined different levels of phosphate fertilization with foliar phosphite application, the 500 mM dose proved effective in suppressing Bidens pilosa development under low phosphate availability, highlighting the potential of this strategy to manage invasive species in rice systems. Moreover, both transgenic and wild-type (WT) rice plants maintained or even improved their photosynthetic and phenotypic parameters, indicating that foliar phosphite application can benefit mineral nutrition of plants capable of metabolizing it, without harming conventional plants. In summary, foliar phosphite application technology combined with the use of genetically modified plants represents a promising integrated weed management strategy in rice cultivation, reconciling nutritional efficiency and selective control, with the potential to contribute to the sustainability and resilience of agricultural systems facing increasingly urgent climate challenges.

COMMITTEE MEMBERS:
Interno - 1399485 - ANDRES CALDERIN GARCIA
Presidente - 2626406 - LEANDRO AZEVEDO SANTOS
Externo à Instituição - VINICIUS MIRANDA DE SOUZA - IFRR