Banca de DEFESA: ANA CAROLINA OLIVEIRA CHAPETA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ANA CAROLINA OLIVEIRA CHAPETA
DATE: 19/05/2025
TIME: 08:30
LOCAL: On-line
TITLE:

Monitoring the resistance of species of the genus Amaranthus in soybean production areas

KEY WORDS:

herbicide resistance; dose-response curve; caruru; Amaranthus hybridus; Amaranthus retroflexus; Amaranthus spinosus; Amaranthus viridis; Amaranthus lividus

PAGES: 115
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Fitotecnia
SPECIALTY: Matologia
SUMMARY:

The expansion of agricultural areas with glyphosate-resistant crops (RR crops) has contributed to the selection of resistant biotypes of weeds. Species of the genus Amaranthus have presented this problem due to their great ability to survive, multiply and the similarities between species of this genus. The objectives of this study were to monitor the dispersion of biotypes of species of the genus Amaranthus resistant to glyphosate, propose management alternatives, identify and characterize the different resistant species found in soybean producing areas. In chapter 1, the monitoring of populations of the genus Amaranthus, suspected of resistance to the herbicide glyphosate, was carried out through the screening of 35 biotypes collected between the states of Rio Grande do Sul and São Paulo in areas with control failures. Then, the identification of the species found and production of exsiccates were carried out. The species found were: Amaranthus hybridus (17 with susp. of resistance and 4 susceptible), Amaranthus retroflexus (6 with susp. of resistance and 2 susceptible), Amaranthus spinosus (1 with susp. of resistance), Amaranthus viridis (3 with susp. of resistance and 1 susceptible), Amaranthus lividus (1 with susp. of resistance). In chapter 2, the resistance of the Amaranthus biotypes monitored in trial 1 was evaluated, through dose-response curves, to the herbicide glyphosate. From the 17 biotypes of Amaranthus hybridus, 6 biotypes of Amaranthus retroflexus and 3 biotypes of Amaranthus viridis, it can be concluded from the dose-response curve tests that they are resistant to the herbicide glyphosate. And the susceptible biotypes presented 100% control at the dose of 1200 g ae ha-1 . In chapter 3, management alternatives were tested for the control of Amaranthus hybridus through the use of pre- and post-emergence herbicides recommended for soybean crops. For the control of pigweed in post-emergence, the herbicide flumioxazin is recommended. The herbicides flumioxazin and diclosulam are an effective alternative for the pre-emergence management of Amaranthus hybridus, without resistance to these molecules. Chapter 4 aimed to compare the anatomy of biotypes resistant and susceptible to the herbicide glyphosate of Amaranthus retroflexus and Amaranthus hybridus. A. retroflexus and A. hybridus presented leaf blades with characteristics typical of plants with C4 metabolism. Among the resistant and susceptible biotypes of A. retroflexus, the resistant biotype presented a lower density of stomata and trichomes; the opposite occurred in A. hybridus. A. retroflexus has smaller intercellular spaces in the chlorophyll tissue. Pigment levels did not show statistically significant differences. The identification of resistant biotypes through constant monitoring of crops will probably prevent the spread of resistance in the area, avoiding the increase in the soil seed bank and, consequently, reducing the costs and impact of managing these biotypes.

COMMITTEE MEMBERS:
Interno - 1905333 - AROLDO FERREIRA LOPES MACHADO
Presidente - 2466219 - CAMILA FERREIRA DE PINHO
Externa à Instituição - GABRIELA DE SOUZA DA SILVA - UFRRJ
Externo à Instituição - JUNIOR BORELLA - FURG
Externo à Instituição - Paulo Vinicius da Silva - USP