Made available in DSpace on 2014-06-11T19:30:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-09-10Bitstream added on 2014-06-13T21:01:04Z : No. of bitstreams: 1 cavalieri_sd_dr_botfca.pdf: 541032 bytes, checksum: 35c98291dc7bcdb9b1ec86f4f88d72ba (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O estudo da seletividade e dos efeitos secundários dos herbicidas nas culturas agrícolas é de extrema importância para o sucesso da agricultura. No presente trabalho, três experimentos foram realizados. O primeiro, conduzido em casa-de-vegetação localizada na Faculdade de Ciências Agronômicas, UNESP, Campus de Botucatu (SP), teve como objetivo avaliar o efeito de formulações comerciais de glyphosate em parâmetros nutricionais e acúmulo de matéria seca de duas cultivares de soja RR resistentes ao glyphosate. Os tratamentos avaliados resultaram do arranjo fatorial entre formulações de glyphosate (Roundup Original®, Roundup Ready®, Roundup Transorb®, Roundup WG®, Roundup Ultra® e Zapp Qi®), mais uma testemunha e cultivares de soja RR (CD 225 RR e V Max RR), conduzidos em delineamento de blocos completos casualizados com seis repetições. As aplicações dos herbicidas ocorreram quando as plantas de soja apresentavam-se no estádio V3 (25 dias após a emergência), na dosagem de 960 g e.a. ha-1. Transcorridos 15 dias após o tratamento, a parte aérea das plantas de soja foi colhida e seca em estufa. Depois de secas, obtiveram-se os dados de massa da matéria seca de hastes, folhas e parte aérea (hastes + folhas), sendo em seguida o material triturado e enviado para laboratório para análise dos teores de macronutrientes (N, P, K, Ca, Mg e S) e micronutrientes (Cu, Fe, Mn, Zn e B). Após isso, de posse dos resultados das análises laboratoriais, calculou-se o acúmulo de nutrientes na parte aérea de cada planta presente nos vasos. De forma geral, o acúmulo de macronutrientes, micronutrientes e matéria seca na parte aérea das plantas de soja sempre foi maior na cultivar V Max RR em relação à CD 225 RR. As formulações Roundup Ready® e Roundup Ultra®, não apresentaram problemas no que diz respeito ao acúmulo de nutrientes e matéria seca na parte aérea... / The study of selectivity and secondary effects of herbicides on crops is extremely important to the success of agriculture. In this study, three experiments were conducted. The first one, carried out in a greenhouse located at the College of Agronomic Sciences, UNESP, Botucatu (SP), aimed to evaluate the effect of commercial formulations of glyphosate on nutritional status and dry matter accumulations in two glyphosate-resistant soybeans cultivars (GR). The treatments were arranged in a factorial arrangement involving six commercial formulations of glyphosate Roundup Original®, Roundup Ready®, Roundup Transorb®, Roundup WG®, Roundup Ultra® and Zapp Qi® plus a control treatment, and two soybean cultivars (CD 225 RR and V Max RR), arranged in a randomized complete block design replicated six times. The herbicide applications occurred when the soybean plants were at V3 growth stage (25 days after emergence) using a dose of 960 g a.e. ha-1. After 15 days after application, the shoot of soybeans was harvested and dried in an oven. Once dried, we obtained data of dry matter of stems, leaves and shoots (stems + leaves), and then the plants were crushed and sent to the laboratory for analysis of macronutrients (N, P, K, Ca, Mg and S) and micronutrients (Cu, Fe, Mn, Zn and B). After that, ownership of the results of nutritional analysis, we calculated the accumulation of nutrients in the shoots in each plant of the pots. In general, the accumulation of macronutrients, micronutrients and dry matter in the shoot of soybean plants was always greater in V Max RR cultivar than CD 225 RR cultivar. The formulations Roundup Ready®, Roundup Ultra® and Zapp QI® showed no problems in regard to the accumulation of nutrients in shoots of cultivars. Furthermore, the Roundup Original®, Roundup Transorb® and Roundup WG® formulations caused the greatest damage to the nutrition provided the cultivars... (Complete abstract click electronic access below)

The first case of field evolved acetolactate synthase (ALS) inhibiting herbicide resistance in the model plant, mouse-ear cress, was reported in winter wheat fields in Westmoreland County, Virginia. A putative resistant (R) mouse-ear population was assessed for ALS resistance relative to a putative susceptible (S) and a susceptible lab population Columbia (C). Results indicated that the R population needed 23 to >2400 fold rate of thifensulfuron relative to S or C population, and it has evolved cross-resistance to sulfonylureas (SU), triazolopyrimidine sulfonanilides (TP), and sulfonylaminocarbonyltriazolinones (SCT). Further studies sequenced the whole genome for four field populations, representing two locations and two resistance levels (high and low) per location, to characterize the genetic mechanism of ALS resistance. The results revealed that all populations contained mutations in the ALS gene at the Pro197 site, although the Pro was substituted by Phe in one location and Thr in the other. Also, both high- and low-level resistant plants at one location had additional mutations (Trp574Leu or Asp376Glu) known to confer resistance to ALS inhibiting herbicides. Patterns of herbicide cross-resistance also varied among the populations. Additionally, research was conducted to assess preemergent (PRE) and postemergent (POST) alternative herbicide options for control of ALS resistant mouse-ear cress and its interference with winter wheat. Results indicate flumioxazin, pyroxasulfone, and metribuzin can be used for effective PRE control whereas 2,4-D, dicamba, and metribuzin can be effective post control options. No mouse-ear cress interference with winter wheat was observed at density of more than 300 plants m-2. / Master of Science in Life Sciences

Herbicide combinations are common in corn production in the United States to control broadleaf and grass weed species. Studies were conducted in 1995 and 1996 to: (1) investigate the interactions of 2,4-D and dicamba with halosulfuron-methyl on common lambsquarters and common ragweed control in corn, (2) determine the effect of 2,4-D on the foliar absorption, translocation, and metabolism of 14C halosulfuron-methyl in common lambsquarters, (3) examine the interactions of 2,4-D, dicamba, and ALS-inhibitor herbicides with rimsulfuron plus thifensulfuron-methyl (RT) and with sethoxydim on giant foxtail, common ragweed, and common lambsquarters control in corn. Combinations of halosulfuron-methyl with 2,4-D or dicamba were generally additive in their effects on common lambsquarters and common ragweed control, and were occasionally synergistic on common lambsquarters. Synergistic herbicide interactions in the greenhouse were observed with 2,4-D (17 g/ha ) and halosulfuron-methyl (18 g/ha) and 2,4-D (70 g/ha ) in combination with halosulfuron-methyl at 4.5 and 36 g/ha, respectively. Absorption and translocation of 14C-halosulfuron-methyl were not influenced by the addition of 2,4-D, with absorption increasing with time. Three unknown halosulfuron-methyl metabolites (M1, M2, and M3) with Rf values of 0.0, 0.97, and 0.94, respectively, were isolated. The addition of 2,4-D increased the level of M3 at the 18 g/ha halosulfuron-methyl rate, which may contribute to common lambsquarters phytotoxicity. Antagonism on giant foxtail control was observed with all combinations of RT and 2,4-D. Tank mixtures of RT with flumetsulam plus clopyralid plus 2,4-D, atrazine, 2,4-D, and dicamba plus atrazine controlled giant foxtail £ 78% 65 (DAT). RT mixed with flumetsulam plus clopyralid plus 2,4-D injured corn 26%, and yields were reduced 34% when compared to RT alone. Giant foxtail control from sethoxydim tank-mixed with bentazon plus atrazine with urea ammonium nitrate (UAN), or with ALS-inhibiting herbicides except halosulfuron-methyl in combination with 2,4-D was 24% lower when averaged over treatments. Yields of sethoxydim-resistant (SR) corn treated with sethoxydim mixed with combinations of sulfonylurea herbicides plus 2,4-D were low, with the exception of the combination halosulfuron-methyl with sethoxydim and 2,4-D. These studies indicate that thoroughly understanding postemergence (POST) corn herbicide tank mixtures is crucial for effective weed management. / Ph. D.

Mundialmente, a soja é considerada uma das principais fontes de produção de óleos e proteínas vegetais para alimentação humana e animal. Constitui-se atualmente um dos produtos de maior importância na economia brasileira. É notório o crescimento das áreas ocupadas pelas lavouras de soja no Brasil, que na safra 2014/2015 atingiram 32,09 milhões de hectares, com previsão de expansão para 32,20 milhões de hectares para a safra 2015/2016. Outro aspecto a ser salientado é que as lavouras de soja RR (Roundup Ready) corresponderam a 93,5%, da área total cultivada com soja no Brasil na safra 2014/2015. Cultivares STS (Soja Tolerante à Sulfoniluréias) contém um gene que aumenta a degradação de alguns herbicidas na planta, como por exemplo, o chlorimuron-ethyl, para o qual são posicionados tolerando doses até quatro vezes as doses recomendadas para cultivares não tolerantes, sem apresentar danos significativos. A soja STS foi desenvolvida através da técnica de mutagênese de sementes utilizando o agente alquilante etilmetanosulfonato (EMS), não sendo uma cultura transgênica. Os objetivos do presente trabalho foram: avaliar a seletividade do herbicida chlorimuron-ethyl aplicado em pós-emergência de soja RR/STS; avaliar a seletividade de herbicidas inibidores da ALS aplicados em pós-emergência de soja RR/STS. Para tanto foram conduzidos dois experimentos principais. O primeiro conduzido durante quatro safras (2011/2012 a 2014/2015), os tratamentos foram constituídos por sete doses do herbicida chlorimuron-ethyl (0, 15, 30, 45, 60, 75 e 90 g i. a. ha-1). Foi realizada avaliação das variáveis relacionadas ao desempenho agronômico (altura, número de vagens por planta, produtividade, e massa de mil sementes). O segundo durante a safra 2014/2015 no campo e casa de vegetação, em que a soja RR/STS foi submetida à aplicação de herbicidas inibidores da ALS, associados ou não ao glyphosate. Foi realizada avaliação de fitointoxicação, índice SPAD, bem como variáveis relacionadas ao desempenho agronômico para o experimento no campo (número de vagens por planta e produtividade). Os cultivares de soja CD 250 e CD 2630 RR/STS apresentaram-se tolerantes para aplicação, em pós-emergência (V4), do herbicida chlorimuron-ethyl até a dose de 90 g i. a. ha-1. O cultivar de soja CD 2630 RR/STS apresentou-se tolerante à aplicação, em pós-emergência, dos herbicidas utilizados, isolada ou em associação com glyphosate. Exceção feita ao metsulfuron-methy (2,4 g i. a. ha-1), associado ou não com glyphosate (960 g e. a. ha-1). / Worldwide soybean is considered one of the major sources of production of vegetable oils and proteins for food and feed. It currently is one of the most important products in the Brazilian economy. It is notable growth areas occupied by soybean crops in Brazil, that in the 2014/2015 season reached 32.09 million hectares, with expansion forecast to 32.20 million hectares for the season 2015/2016. Another aspect to be noted is that the RR soybean (Roundup Ready) crops corresponded to 93.5% of the total area cultivated with soybeans in Brazil in the 2014/2015 season. Cultivars STS (Sulfonylurea Tolerant Soybeans) contains a gene that increases the degradation of some herbicides in the plant, for example, chlorimuron-ethyl, to which are positioned tolerated doses up to four times the recommended dosages for nontolerant cultivars, without presenting significant damage. STS soybean was developed by seed mutagenesis technique using the alkylating agent ethyl methane sulfonate (EMS), not being a transgenic crop. The aims of this study were to evaluate the selectivity of the herbicide chlorimuron-ethyl applied post-emergence of RR/STS soybean; evaluate the selectivity of ALS-inhibiting herbicides applied postemergence of RR/STS soybean. Therefore, two main experiments were conducted. The first conducted for four seasons (2011/2012 to 2014/2015), the treatments were seven doses of the herbicide chlorimuron-ethyl (0, 15, 30, 45, 60, 75 and 90 g a. i. ha-1). Performed an assessment of variables related to agronomic performance (height, number of pods per plant, yield and mass of one thousand seeds). The second during the 2014/2014 season in the field and the greenhouse, where RR/STS soybean was subjected to application of ALS inhibitor herbicides, with or without glyphosate. It was conducted evaluation phytointoxication, SPAD index, as well as variables related to agronomic performance (number of pods per plant and productivity). The soybean cultivars CD 250 and CD 2630 RR/STS were tolerant to application, post-emergence (V4) of herbicide chlorimuron-ethyl up to a dose of 90 g a. i. ha-1. Cultivar CD 2630 RR/STS presented tolerance to application in postemergence herbicides used alone or in combination with glyphosate. Except for the metsulfuron-methy (2.4 g a. i. ha-1), associated or not with glyphosate (960 g a. e. ha-1).

Mundialmente, a soja é considerada uma das principais fontes de produção de óleos e proteínas vegetais para alimentação humana e animal. Constitui-se atualmente um dos produtos de maior importância na economia brasileira. É notório o crescimento das áreas ocupadas pelas lavouras de soja no Brasil, que na safra 2014/2015 atingiram 32,09 milhões de hectares, com previsão de expansão para 32,20 milhões de hectares para a safra 2015/2016. Outro aspecto a ser salientado é que as lavouras de soja RR (Roundup Ready) corresponderam a 93,5%, da área total cultivada com soja no Brasil na safra 2014/2015. Cultivares STS (Soja Tolerante à Sulfoniluréias) contém um gene que aumenta a degradação de alguns herbicidas na planta, como por exemplo, o chlorimuron-ethyl, para o qual são posicionados tolerando doses até quatro vezes as doses recomendadas para cultivares não tolerantes, sem apresentar danos significativos. A soja STS foi desenvolvida através da técnica de mutagênese de sementes utilizando o agente alquilante etilmetanosulfonato (EMS), não sendo uma cultura transgênica. Os objetivos do presente trabalho foram: avaliar a seletividade do herbicida chlorimuron-ethyl aplicado em pós-emergência de soja RR/STS; avaliar a seletividade de herbicidas inibidores da ALS aplicados em pós-emergência de soja RR/STS. Para tanto foram conduzidos dois experimentos principais. O primeiro conduzido durante quatro safras (2011/2012 a 2014/2015), os tratamentos foram constituídos por sete doses do herbicida chlorimuron-ethyl (0, 15, 30, 45, 60, 75 e 90 g i. a. ha-1). Foi realizada avaliação das variáveis relacionadas ao desempenho agronômico (altura, número de vagens por planta, produtividade, e massa de mil sementes). O segundo durante a safra 2014/2015 no campo e casa de vegetação, em que a soja RR/STS foi submetida à aplicação de herbicidas inibidores da ALS, associados ou não ao glyphosate. Foi realizada avaliação de fitointoxicação, índice SPAD, bem como variáveis relacionadas ao desempenho agronômico para o experimento no campo (número de vagens por planta e produtividade). Os cultivares de soja CD 250 e CD 2630 RR/STS apresentaram-se tolerantes para aplicação, em pós-emergência (V4), do herbicida chlorimuron-ethyl até a dose de 90 g i. a. ha-1. O cultivar de soja CD 2630 RR/STS apresentou-se tolerante à aplicação, em pós-emergência, dos herbicidas utilizados, isolada ou em associação com glyphosate. Exceção feita ao metsulfuron-methy (2,4 g i. a. ha-1), associado ou não com glyphosate (960 g e. a. ha-1). / Worldwide soybean is considered one of the major sources of production of vegetable oils and proteins for food and feed. It currently is one of the most important products in the Brazilian economy. It is notable growth areas occupied by soybean crops in Brazil, that in the 2014/2015 season reached 32.09 million hectares, with expansion forecast to 32.20 million hectares for the season 2015/2016. Another aspect to be noted is that the RR soybean (Roundup Ready) crops corresponded to 93.5% of the total area cultivated with soybeans in Brazil in the 2014/2015 season. Cultivars STS (Sulfonylurea Tolerant Soybeans) contains a gene that increases the degradation of some herbicides in the plant, for example, chlorimuron-ethyl, to which are positioned tolerated doses up to four times the recommended dosages for nontolerant cultivars, without presenting significant damage. STS soybean was developed by seed mutagenesis technique using the alkylating agent ethyl methane sulfonate (EMS), not being a transgenic crop. The aims of this study were to evaluate the selectivity of the herbicide chlorimuron-ethyl applied post-emergence of RR/STS soybean; evaluate the selectivity of ALS-inhibiting herbicides applied postemergence of RR/STS soybean. Therefore, two main experiments were conducted. The first conducted for four seasons (2011/2012 to 2014/2015), the treatments were seven doses of the herbicide chlorimuron-ethyl (0, 15, 30, 45, 60, 75 and 90 g a. i. ha-1). Performed an assessment of variables related to agronomic performance (height, number of pods per plant, yield and mass of one thousand seeds). The second during the 2014/2014 season in the field and the greenhouse, where RR/STS soybean was subjected to application of ALS inhibitor herbicides, with or without glyphosate. It was conducted evaluation phytointoxication, SPAD index, as well as variables related to agronomic performance (number of pods per plant and productivity). The soybean cultivars CD 250 and CD 2630 RR/STS were tolerant to application, post-emergence (V4) of herbicide chlorimuron-ethyl up to a dose of 90 g a. i. ha-1. Cultivar CD 2630 RR/STS presented tolerance to application in postemergence herbicides used alone or in combination with glyphosate. Except for the metsulfuron-methy (2.4 g a. i. ha-1), associated or not with glyphosate (960 g a. e. ha-1).

Orientador: Edivaldo Domingues Velini / Banca: João Domingos Rodrigues / Banca: Robinson Antonio Pitelli / Banca: Robinson Osipe / Banca: Cleber Daniel de Goes Maciel / Resumo: O estudo da seletividade e dos efeitos secundários dos herbicidas nas culturas agrícolas é de extrema importância para o sucesso da agricultura. No presente trabalho, três experimentos foram realizados. O primeiro, conduzido em casa-de-vegetação localizada na Faculdade de Ciências Agronômicas, UNESP, Campus de Botucatu (SP), teve como objetivo avaliar o efeito de formulações comerciais de glyphosate em parâmetros nutricionais e acúmulo de matéria seca de duas cultivares de soja RR resistentes ao glyphosate. Os tratamentos avaliados resultaram do arranjo fatorial entre formulações de glyphosate (Roundup Original®, Roundup Ready®, Roundup Transorb®, Roundup WG®, Roundup Ultra® e Zapp Qi®), mais uma testemunha e cultivares de soja RR (CD 225 RR e V Max RR), conduzidos em delineamento de blocos completos casualizados com seis repetições. As aplicações dos herbicidas ocorreram quando as plantas de soja apresentavam-se no estádio V3 (25 dias após a emergência), na dosagem de 960 g e.a. ha-1. Transcorridos 15 dias após o tratamento, a parte aérea das plantas de soja foi colhida e seca em estufa. Depois de secas, obtiveram-se os dados de massa da matéria seca de hastes, folhas e parte aérea (hastes + folhas), sendo em seguida o material triturado e enviado para laboratório para análise dos teores de macronutrientes (N, P, K, Ca, Mg e S) e micronutrientes (Cu, Fe, Mn, Zn e B). Após isso, de posse dos resultados das análises laboratoriais, calculou-se o acúmulo de nutrientes na parte aérea de cada planta presente nos vasos. De forma geral, o acúmulo de macronutrientes, micronutrientes e matéria seca na parte aérea das plantas de soja sempre foi maior na cultivar V Max RR em relação à CD 225 RR. As formulações Roundup Ready® e Roundup Ultra®, não apresentaram problemas no que diz respeito ao acúmulo de nutrientes e matéria seca na parte aérea... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The study of selectivity and secondary effects of herbicides on crops is extremely important to the success of agriculture. In this study, three experiments were conducted. The first one, carried out in a greenhouse located at the College of Agronomic Sciences, UNESP, Botucatu (SP), aimed to evaluate the effect of commercial formulations of glyphosate on nutritional status and dry matter accumulations in two glyphosate-resistant soybeans cultivars (GR). The treatments were arranged in a factorial arrangement involving six commercial formulations of glyphosate Roundup Original®, Roundup Ready®, Roundup Transorb®, Roundup WG®, Roundup Ultra® and Zapp Qi® plus a control treatment, and two soybean cultivars (CD 225 RR and V Max RR), arranged in a randomized complete block design replicated six times. The herbicide applications occurred when the soybean plants were at V3 growth stage (25 days after emergence) using a dose of 960 g a.e. ha-1. After 15 days after application, the shoot of soybeans was harvested and dried in an oven. Once dried, we obtained data of dry matter of stems, leaves and shoots (stems + leaves), and then the plants were crushed and sent to the laboratory for analysis of macronutrients (N, P, K, Ca, Mg and S) and micronutrients (Cu, Fe, Mn, Zn and B). After that, ownership of the results of nutritional analysis, we calculated the accumulation of nutrients in the shoots in each plant of the pots. In general, the accumulation of macronutrients, micronutrients and dry matter in the shoot of soybean plants was always greater in V Max RR cultivar than CD 225 RR cultivar. The formulations Roundup Ready®, Roundup Ultra® and Zapp QI® showed no problems in regard to the accumulation of nutrients in shoots of cultivars. Furthermore, the Roundup Original®, Roundup Transorb® and Roundup WG® formulations caused the greatest damage to the nutrition provided the cultivars... (Complete abstract click electronic access below) / Doutor

<p>Acetolactate synthase (ALS) inhibitors are a widely used class of selective herbicides used to control grass and broadleaf weeds. The repeated use of ALS-inhibiting herbicides has selected for biotypes of weeds resistant to ALS inhibitors, especially in the weeds most problematic to growers in the Midwest. While ALS inhibitor use seems futile, new mechanisms of herbicide action are not predicted to be commercialized in the near future to solve this problem. This leads to the main objective of this research, determining what value ALS inhibitors provide in controlling populations of weeds with resistance to ALS inhibitors. </p> <p>Field experiments with soil-applied (PRE) applications of ALS inhibitors on horseweed (<i>Erigeron canadensis</i>) and tall waterhemp (<i>Amaranthus tuberculatus </i>var. <i>rudis</i>) exhibited higher efficacy than would be expected given the frequency of the ALS resistance trait in the population. Whereas control of these species with POST-applied applications was similar or less than the proportion of the population characterized as susceptible using molecular techniques. Soil-applied applications, therefore, resulted in relatively greater control than POST applications in populations with known ALS-inhibitor-resistance mechanisms.</p> <p>Greenhouse experiments showed that overall resistance ratios were higher for PRE applications of ALS inhibitors in horseweed, tall waterhemp, and Palmer amaranth (<i>Amaranthus palmeri</i>). However, GR₅₀ values decreased for both susceptible and resistant biotypes for the PRE applications compared to POST, suggesting the biologically effective dose of these herbicides is lower in soil residual applications. This research found that PRE applications of ALS inhibitors resulted in some level of control on horseweed and tall waterhemp classified as resistant to ALS inhibitors due to the higher efficacy of PRE herbicide applications.</p> <p>Genetic analysis assessing the amino acid substitutions that confer resistance to ALS inhibitors in tall waterhemp confirmed a difference in selection pressure between PRE and POST applications and between ALS active ingredients in tall waterhemp. Applications of chlorimuron PRE at 11 g ai ha^-1selected for 35% homozygous W574L genotypes and at 44 g ha^-1 selected for 70% homozygous W574L genotypes. An increase of homozygous W574L individuals along with a decrease in heterozygous individuals from 65 (11 g ha^-1) to 29% (44 g ha^-1) suggests that W574L is semi-dominant in tall waterhemp and that high labeled rates of chlorimuron applied PRE can partially overcome the heterozygous W574L-resistance mechanism. In horseweed, no difference in selection pressure was observed between application timing or between chlorimuron or cloransulam. A new mutation conferring ALS-inhibitor resistance in horseweed was discovered, a Pro197Leu amino acid substitution, with resistance ratios of 21X to chlorimuron and 8.6X to cloransulam. These resistance ratios are slightly less than those reported for the Pro197Ala and Pro197Ser amino acid substitutions in conferring ALS-inhibitor resistance in horseweed. </p> <p>Finally, a survey of 42 populations of tall waterhemp in Indiana counties with confirmed ALS-inhibitor resistant populations of tall waterhemp found that all populations contained at least 16% individuals with the W574L amino acid substitution, 35 populations contained at least 1% individuals with the S653N substitution, and 9 populations contained at least 1% individuals with the S653T substitution. Taking into consideration the three mutations tested, 8 of the 42 populations tested contained <50% ALS-inhibitor resistant individuals within the population. Using the same tall waterhemp populations as collected in the survey, Next-Generation Sequencing was used to determine if other amino acid substitutions conferring resistance to ALS inhibitors existed. Results from WideSeq revealed that 10 other amino acid substitutions in the ALS protein may be conferring resistance in tall waterhemp in Indiana: A122T, A122N, A122S, P197T, P197L, P197H, D376E, and G654F. Further research from this survey also suggests that metabolic resistance to ALS inhibitors is likely a contributor to resistance in tall waterhemp in Indiana.</p> <p>This research suggests that ALS-inhibiting herbicides, more specifically chlorimuron, would provide the greatest contribution to management of tall waterhemp. Chlorimuron would perform best when used in soil residual applications and in populations of tall waterhemp containing either individuals susceptible to chlorimuron or individuals heterozygous for ALS inhibitor resistance conferred by the W574L mutation. This research also demonstrates the specificity of the amino acid substitutions in the ALS protein and by weed species to realize the benefit of these herbicides for management of weeds resistant to ALS inhibitors. Molecular characterization of target site resistance to ALS inhibitors has traditionally been considered relatively simple. However, we found 11 new amino acid substitutions that confer resistance to ALS inhibitors in horseweed and tall waterhemp. The complexity of ALS inhibitor resistance calls for the use of methods such as NGS to detect all potential resistance mutations in a timely manner and for the use of tests detecting metabolic resistance. Overall, this research demonstrates that ALS inhibitors still provide some utility for management of weed populations classified as resistant to ALS inhibitors and that the resistance mechanisms in horseweed and tall waterhemp are more numerous than previously reported. </p>

Ce travail a eu pour but premier d’étudier le risque d’évolution de la résistance aux herbicides inhibiteurs de l’acétolactate synthase (ALS) chez l’ambroisie à feuilles d’armoise (Ambrosia artemisiifolia L.) à travers quatre points : (i) la pression de sélection (étude de l’efficacité d’une gamme d'herbicides inhibiteurs de l’ALS), (ii) la capacité de réponse adaptative de l’adventice (détermination de la variation de la sensibilité aux inhibiteurs de l’ALS entre plantes et mise en place d’un programme de sélection récurrente), (iii) une étude de terrain (recherche de résistance aux inhibiteurs de l’ALS au champ en France), (iv) l’étude des mécanismes de résistance (liée à la cible – RLC – et non liée à la cible – RNLC – par une approche de transcriptomique). Le second objectif fut d’étudier la connectivité des populations d’A. artemisiifolia dans des paysages agricoles à l’aide de marqueurs microsatellites développés lors de ce travail afin de déterminer les facteurs qui pourraient faciliter la dispersion de cette espèce et de la résistance à l’échelle du paysage agricole.En ce qui concerne la résistance aux herbicides :-La réponse de d’A. artemisiifolia aux herbicides inhibiteurs de l’ALS est très variable entre substances.-Des plantes ayant survécu à la dose maximale autorisée et à des doses supérieures de metsulfuron ont été sélectionnées pour débuter un programme de sélection récurrente. Après deux cycles de sélection, on observe une intensification de la résistance au metsulfuron et une émergence de la résistance à l’imazamox et au tribénuron.-Trois cas de résistance à l’imazamox ont été identifiés au champ dont deux cas de pure RNLC et un cas de coexistence RLC – RNLC.-Un transcriptome d’A. artemisiifolia a été généré grâce à la technique de séquençage PacBio pour rechercher des gènes impliqués dans les mécanismes de RNLC (approche RNAseq). 62 gènes candidats ont été identifiés dont des transporteurs ABC, des cytochromes P450 ainsi que des glutathione-S-transférases connus pour être impliqués dans la dégradation des herbicides.Pour l’étude de la connectivité des populations agricoles :-26 marqueurs microsatellites ont été développés et ont révélé une forte variabilité génétique. La structuration génétique a été étudiée à grande échelle pour des populations d’A. artemisiifolia d’Europe (aire d’invasion) et d’Amérique du Nord (aire d’origine).-À une échelle plus fine (paysage agricole), la structure génétique des populations reste influencée par les événements de colonisation. Les événements de migration qui ont été identifiés entre zones de présence de l’ambroisie suggèrent des flux de gènes (pollen/semences) et une connectivité modérés à l’échelle d’un territoire agricole. Dans les environnements agricoles, la dispersion des allèles de résistance aux herbicides pourrait se faire facilement de proche en proche via les flux de pollen, et également à plus longue distance via des dispersions de graines. Les activités anthropiques jouent un rôle majeur dans la dispersion des semences (machineries agricoles, lots de semences contaminés…).-L’analyse du système de reproduction a confirmé que cette espèce est allogame ce qui entraîne des flux de gènes intra- et inter-populations importants.Les connaissances acquises au cours de ce travail pourront aider à développer des stratégies de contrôle mieux adaptées, pour lutter efficacement contre A. artemisiifolia afin de limiter son expansion, telles que :-Des stratégies de désherbage diversifiées : combinaison de lutte mécanique (dont faux semis) et chimique (diversification des modes d’action herbicides).-Un allongement et une diversification des rotations de cultures en favorisant des cultures d’hiver et/ou des cultures couvrantes et compétitrices.Ces connaissances pourront aussi être utilisées dans la lutte contre une autre espèce adventice du genre Ambrosia, Ambrosia trifida.Mots-clés (6) : Ambrosia artemisiifolia L., ambroisies, résistance aux herbicides, / The first aim of this work was to investigate the risk for the evolution of resistance to acetolactate synthase inhibitor (ALS) herbicides in the common ragweed (Ambrosia artemisiifolia L.) through four points: (i) the selection pressure (effectiveness of a range of ALS inhibitor herbicides), (ii) the adaptive response of Ambrosia artemisiifolia (recurrent selection experiment), (iii) a resistance monitoring in fields in France, and (iv) the investigation of the mechanisms underlying herbicide resistance (target-site (TSR) and non-target-site resistance (NTSR) using transcriptomic analyses). The second aim was to study the connectivity of A. artemisiifolia populations in agricultural landscapes using microsatellite markers developed during this work, to determine factors that could facilitate the spread of this invasive weed species and the spread of herbicide resistance.In regards to herbicide resistance:-The sensitivity of A. artemisiifolia to ALS-inhibiting herbicides is variable between active ingredients.-Plants that survived the French maximum authorized field rate and higher rates of metsulfuron were selected to implement a recurrent breeding program. After two selection cycles, the resistance level to metsulfuron increased and resistance to imazamox and tribenuron emerged.-Three cases of imazamox resistance were identified in the field, including two cases of pure NTSR and one case of TSR - NTSR coexistence.-A transcriptome for A. artemisiifolia, AMBELbase, was generated using the PacBio sequencing technology to search for genes involved in NTSR mechanisms (RNAseq approach). 62 candidate contigs were identified including ABC transporters, cytochromes P450 and glutathione S-transferases known to be involved in the degradation of herbicides.In regards to population connectivity:-26 microsatellite markers were developed and revealed high genetic variability. Genetic structuring has been studied on a large scale for populations of A. artemisiifolia from Europe (invasion range) and North America (native range).-On a finer scale (agricultural landscape), the genetic structure of populations was influenced by colonization events. Migration events detected among the areas colonized by A. artemisiifolia suggested moderate pollen/seed flows and connectivity at the farmland scale. In agricultural environments, herbicide resistant alleles could be easily spread among neighbouring populations via pollen flow, and also at longer distances via seed dispersal. Human-related activities play a major role in the dispersal of seeds (agricultural machinery, contaminated seed lots, etc.).-The mating system analysis confirmed that A. artemisiifolia is an obligate outcrossing species which leads to important intra- and inter-population gene flow.The knowledge acquired during this work may help to foster the development of better management strategies to effectively control A. artemisiifolia to limit its spread, such as:-Diversified weed control strategies: combination of mechanical (including false-seed) and chemical weeding (diversification of herbicide modes of action).-Longer diversified crop rotations including more winter crops and/or cover and competitive crops to break the life cycle of A. artemisiifolia.These knowledge may also be used to better control of another weed species of the genus Ambrosia, Ambrosia trifida L.