京都大学 / 0048 / 新制・論文博士 / 博士(農学) / 乙第12881号 / 論農博第2808号 / 新制||農||1028(附属図書館) / 学位論文||H26||N4880(農学部図書室) / 31599 / (主査)教授 冨永 達, 教授 奥本 裕, 教授 宮川 恒 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

A planta daninha Amaranthus palmeri é nativa dos Estados Unidos, porém foi pela primeira vez relatada no Brasil no ano de 2015. Embora comprovadamente com resistência múltipla aos herbicidas inibidores da ALS e da EPSPS, até o momento não foram investigadas as bases moleculares da resistência. Além disso, por causa da recente introdução da planta daninha no país, alternativas de manejo com culturas tolerantes a herbicidas necessitam ser estudadas. Sendo assim, os objetivos desse trabalho são de caracterizar a espécie de planta daninha introduzida no país, identificar os mecanismos de resistência aos herbicidas inibidores da ALS e da EPSPS presentes no biótipo, e propor abordagens de manejo em ambientes dos novos eventos transgênicos resistentes a herbicidas. Um bioensaio utilizando marcadores genéticos foi desenvolvido para confirmar que a população coletada no estado do Mato Grosso (BR-R) é A. palmeri, e não A. tuberculatus, outra espécie dióica do gênero Amaranthus. Os resultados de experimentos de curvas de dose-resposta e acúmulo de chiquimato indicaram que a BR-R possui alto nível de resistência, com DL50 de 4.426 e 3.400 g glyphosate ha-1 no primeiro e segundo experimento, respectivamente, mais que o dobro da dose típicamente recomendada para o controle da espécie e, adicionalmente, observou se acúmulo mínimo de chiquimato a concentração de 1 mM nos tecidos das plantas tratadas com o herbicida. BR-R também foi resistente a herbicidas dos grupos químicos das sulfoniluréias e imidazolinonas. O mecanismo de resistência ao glyphosate encontrado nesta população foi a super expressão gência, através do aumento no número de cópias do gene da EPSPS no genoma da planta BR-R, entre 50 e 179 cópias adicionais. Além disso, duas substituições de aminoácidos foram observadas na sequência da ALS, W574L e S653N, conferindo resistência tanto a sulfoniluréias quanto a imidazolinonas. No experimento utilizandos os herbicidas correspondentes às culturas geneticamente modificadas com novos traits de tolerância a herbicidas observou se, de uma forma geral, que as associações de herbicidas apresentaram níveis de controle mais satisfatórios. Assim, esta pesquisa confirma a introdução de da espécie A. palmeri no Brasil, assim como a resistência múltipla aos herbicidas inibidores da EPSPS e da ALS. Seu manejo é mais eficaz através da associação de herbicidas, garantindo assim o uso racional das novas tecnologias de culturas geneticamente modificadas com tolerância a herbicidas. / Palmer Amaranth (Amaranthus palmeri) is a weed species native to the United States, but it was reported in Brazil for the first time in 2015. Despite this population being resistant to EPSPS and ALS inhibitors, the molecular basis of its multiple resistance is unknown up to date. Because of this species introduction to Brazil, alternatives of management with the new herbicide-tolerant crops technologies need to be studied. The objectives of this research are to characterize the weed species introduced to Brazil, identify the mechanisms conferring resistance to ALS and EPSPS inhibitors herbicides, and to propose management approaches in environments with the new genetically modified herbicide-tolerant crops. A genotyping bioassay using genetic markers was developed to confirm that the species collected in the state of Mato Grosso (BR-R) is indeed A. palmeri and not A. tuberculatus, another dioceous species in the Amaranthus genus. Dose-response experiments and shikimate accumulation bioassay data indicate high level of resistance, with LD50 of 4,426 and 3,400 g glyphosate ha-1 in the first and second experiments, respectively, higher than the double rate tipically recommended to control it, and minimal accumulation in BR-R with 1 mM of glyphosate in treated plants in the leaf disks assay. BR-R also was resistanto to sulfonilurea and imidazolinone herbicides. The mechanism conferring resistance to glyphosate identified in this population was gene amplification, with increased EPSPS copy number - between 50 and 179 more copies in BR-R. Besides, two target-site mutations were identified in the ALS gene sequencing, W574L and S653N, conferring resistance to sulfonilureas and imidazolinones. The weed control experiment, overal, herbicide tank mixtures achieved higher levels of control. Therefore, this research confirms the introduction of A. palmeri to Brazil, as well as its multiple resistance to EPSPS and ALS inhibitor herbicides. Its control is more efficient with herbicide mixtures, which guarantees more susteinable use of the new herbicide-tolerant crop technologies.

A planta daninha Amaranthus palmeri é nativa dos Estados Unidos, porém foi pela primeira vez relatada no Brasil no ano de 2015. Embora comprovadamente com resistência múltipla aos herbicidas inibidores da ALS e da EPSPS, até o momento não foram investigadas as bases moleculares da resistência. Além disso, por causa da recente introdução da planta daninha no país, alternativas de manejo com culturas tolerantes a herbicidas necessitam ser estudadas. Sendo assim, os objetivos desse trabalho são de caracterizar a espécie de planta daninha introduzida no país, identificar os mecanismos de resistência aos herbicidas inibidores da ALS e da EPSPS presentes no biótipo, e propor abordagens de manejo em ambientes dos novos eventos transgênicos resistentes a herbicidas. Um bioensaio utilizando marcadores genéticos foi desenvolvido para confirmar que a população coletada no estado do Mato Grosso (BR-R) é A. palmeri, e não A. tuberculatus, outra espécie dióica do gênero Amaranthus. Os resultados de experimentos de curvas de dose-resposta e acúmulo de chiquimato indicaram que a BR-R possui alto nível de resistência, com DL50 de 4.426 e 3.400 g glyphosate ha-1 no primeiro e segundo experimento, respectivamente, mais que o dobro da dose típicamente recomendada para o controle da espécie e, adicionalmente, observou se acúmulo mínimo de chiquimato a concentração de 1 mM nos tecidos das plantas tratadas com o herbicida. BR-R também foi resistente a herbicidas dos grupos químicos das sulfoniluréias e imidazolinonas. O mecanismo de resistência ao glyphosate encontrado nesta população foi a super expressão gência, através do aumento no número de cópias do gene da EPSPS no genoma da planta BR-R, entre 50 e 179 cópias adicionais. Além disso, duas substituições de aminoácidos foram observadas na sequência da ALS, W574L e S653N, conferindo resistência tanto a sulfoniluréias quanto a imidazolinonas. No experimento utilizandos os herbicidas correspondentes às culturas geneticamente modificadas com novos traits de tolerância a herbicidas observou se, de uma forma geral, que as associações de herbicidas apresentaram níveis de controle mais satisfatórios. Assim, esta pesquisa confirma a introdução de da espécie A. palmeri no Brasil, assim como a resistência múltipla aos herbicidas inibidores da EPSPS e da ALS. Seu manejo é mais eficaz através da associação de herbicidas, garantindo assim o uso racional das novas tecnologias de culturas geneticamente modificadas com tolerância a herbicidas. / Palmer Amaranth (Amaranthus palmeri) is a weed species native to the United States, but it was reported in Brazil for the first time in 2015. Despite this population being resistant to EPSPS and ALS inhibitors, the molecular basis of its multiple resistance is unknown up to date. Because of this species introduction to Brazil, alternatives of management with the new herbicide-tolerant crops technologies need to be studied. The objectives of this research are to characterize the weed species introduced to Brazil, identify the mechanisms conferring resistance to ALS and EPSPS inhibitors herbicides, and to propose management approaches in environments with the new genetically modified herbicide-tolerant crops. A genotyping bioassay using genetic markers was developed to confirm that the species collected in the state of Mato Grosso (BR-R) is indeed A. palmeri and not A. tuberculatus, another dioceous species in the Amaranthus genus. Dose-response experiments and shikimate accumulation bioassay data indicate high level of resistance, with LD50 of 4,426 and 3,400 g glyphosate ha-1 in the first and second experiments, respectively, higher than the double rate tipically recommended to control it, and minimal accumulation in BR-R with 1 mM of glyphosate in treated plants in the leaf disks assay. BR-R also was resistanto to sulfonilurea and imidazolinone herbicides. The mechanism conferring resistance to glyphosate identified in this population was gene amplification, with increased EPSPS copy number - between 50 and 179 more copies in BR-R. Besides, two target-site mutations were identified in the ALS gene sequencing, W574L and S653N, conferring resistance to sulfonilureas and imidazolinones. The weed control experiment, overal, herbicide tank mixtures achieved higher levels of control. Therefore, this research confirms the introduction of A. palmeri to Brazil, as well as its multiple resistance to EPSPS and ALS inhibitor herbicides. Its control is more efficient with herbicide mixtures, which guarantees more susteinable use of the new herbicide-tolerant crop technologies.

Sustainable weed control in managed agricultural systems requires the judicious use of multiple weed control tactics and prevents over-reliance on any one tactic. In this context, sustainable weed management plays a critical role in the mitigation of one of agriculture's most pressing problems- herbicide resistance. Research conducted in Virginia sought to explore the effects of integrating multiple weed management tactics in corn and cool-season turfgrass. Additionally, research was conducted to confirm nicosulfuron and glyphosate herbicide resistance in Virginia johnsongrass and elucidate the molecular mechanisms conferring those resistances. Rye and hairy vetch cover crop residues, combined with reduced rates of preemergence herbicide and postemergence glyphosate applications, were shown to provide sufficient weed control and corn yield. Cover crop type or residue level did not augment weed control in corn production systems, but the use of glyphosate was essential for late-season weed control. Rye and vetch biculture as a cover crop increased corn yield compared to rye cover crop alone. In cool-season turfgrass, the addition of reduced preemergence herbicide rates to corn gluten meal, an organic herbicide product, reduced crabgrass 25%. Moreover, control was dependent on herbicide choice. Herbicides applied at half of recommended labeled rates or less did not control crabgrass at a commercially-acceptable level, regardless of corn gluten meal addition. In field experiments, Virginia johnsongrass expressed resistance to nicosulfuron and glyphosate. Glyphosate at 0.88 kg ae ha-1 controlled johnsongrass 65%. Nicosulfuron at 0.14 kg ai ha-1 controlled the same population 10%. Greenhouse experiments confirmed differential sensitivity of putative herbicide-resistant johnsongrass seedlings to nicosulfuron and glyphosate when compared to a susceptible population. Herbicide resistance was not conferred via target-site mutation. Five ALS-gene site mutations were confirmed absent in Virginia johnsongrass, while three others were located in coding regions that could not be elucidated in johnsongrass. Further investigations showed glyphosate resistance was not conferred via reduction in herbicide absorption or translocation. The susceptible johnsongrass caused an increase in a polar metabolite at Rf = 0.17 with concomitant reduction in glyphosate over time. Although the mechanism is not clear, these data suggests that glyphosate resistance in johnsongrass may be associated with differential metabolism. / Ph. D.