Banca de DEFESA: ANA BEATRIZ AMARAL DE MACEDO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : ANA BEATRIZ AMARAL DE MACEDO
DATE: 27/03/2024
TIME: 13:00
LOCAL: Sala 04 DFITO
TITLE:

Conyza sumatrensis resistance mechanism to PSI-inhibiting herbicides

KEY WORDS:

horseweed; diquat; paraquat; photosystem I

PAGES: 71
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Fitotecnia
SPECIALTY: Matologia
SUMMARY:

The weed Conyza sumatrensis (fleabane) is known to exhibit a variety of biotypes resistant to herbicides, further complicating the management of these plants, in addition to their high inherent competitiveness with crops of agronomic interest. Several physiological and genetic factors can influence the resistance of this weed. The objective of this work was to evaluate the mechanisms of fleabane resistance to FSI inhibitor herbicides. The work was divided into two stages, where the first stage was developed in the experimental area of the Weed and Pesticides Research Group (PDPA) at the Federal Rural University of Rio de Janeiro, and in the second stage, the experiment was conducted at the Weed Research Laboratory located at Colorado State University. In the first stage, a dose-response curve to the herbicide diquat was performed, with doses and subdoses of 1/16, 1/8, 1/4, 1/2, 1, 2, 4, 8, and 16 times the label dose (200 g ai L-1) in susceptible (S) and resistant (R) fleabane biotypes acclimatized to different temperatures, 14ºC (F) and 35ºC (Q), where phytotoxicity and transient chlorophyll a fluorescence were analyzed at 3, 6, 12, 24, 48, 72 hours after application (HAA) and at 14, 21, and 28 days after application (DAA), in addition to the dry mass of the aerial part at 28 DAA and LD50 and GR50 analyses. The data obtained in the experiment were subjected to ANOVA (p ≤ 0.05), and the means were compared by Tukey's test at 5% probability. The results showed a difference in the metabolic behavior of plants subjected to S and Q, where RQ presented greater regrowth and an increase in total PI, while RS showed greater DI0/RC at 28 DAA, while SF plants were controlled at 1/2 the dose at 7 DAA, while SQ showed greater herbicide tolerance. The LD50 and GR50 values indicate a higher resistance factor for plants subjected to Q. In the second stage of the work, a Mendelian progeny segregation study was carried out for segregating fleabane biotypes (R♂ x S♀) for the herbicides diquat (200 g ai L-1) and paraquat (400 g ai L-1) subjected to Mendelian models 3:1 for one dominant gene and 15:1 for two dominant and independent genes. The chi-square goodness-of-fit test (χ2) was performed to compare the observed and expected surviving and dead plants, and the model was rejected if p ≤ 0.05. Afterwards, bulked segregant analysis was performed. After DNA extraction from leaf tissue, the samples of S and R biotypes of fleabane to diquat and paraquat herbicides were sequenced. The sequencing data were processed by bioinformatics tools such as SAMtools, BWA FASTP, and GATK and matched with the reference genome provided by the Weed Research Laboratory. The results obtained from the study suggest that resistance to diquat herbicide is multigenic, while resistance to paraquat herbicide is monogenic, and the genes in which they are located are on chromosomes 24 and 14, respectively.

COMMITTEE MEMBERS:
Interna - 2466219 - CAMILA FERREIRA DE PINHO
Externa à Instituição - CRISTINA MOLL HUTHER - UFF
Externa à Instituição - NATÁLIA DA SILVA GARCIA - UFRRJ