Le nématode à kyste du soya (NKS), Heterodera glycines, est la principale cause de pertes économiques chez le soya aux États-Unis. Au Canada, on le retrouve en Ontario depuis 1988 et il continue à gagner du terrain chaque année. Il a été répertorié pour la première fois au Québec en 2013, et les producteurs de soya québécois ont déjà commencé à déployer des outils pour sa répression. La méthode de lutte la plus utilisée contre cet organisme est l’utilisation de gènes de résistance quantitative combiné à la rotation des cultures. Par contre, l’organisme causant le plus de dommages chez le soya à l’heure actuelle au Québec est la pourriture phytophthoréenne, causée par l’oomycète, Phytophthora sojae. Cette maladie racinaire peut, elle aussi, être réprimée grâce à des cultivars génétiquement résistants (résistance qualitative à gènes Rps). Sachant que le NKS se retrouve déjà dans certaines régions du Québec où sévit également P. sojae, il devient urgent de déterminer si les cultivars de soya présentement utilisés exprimeront une résistance satisfaisante contre ces agents pathogènes majeurs. Dans ce contexte, l’objectif principal de ce projet était d’évaluer l’interaction entre ces deux agents pathogènes du soya en fonction de la résistance (qualitative à gènes Rps / résistance quantitative au NKS) des cultivars utilisés. L’étude, réalisée en système hydroponique, a permis de démontrer qu’en présence d’un cultivar sensible aux deux organismes, P. sojae a un impact négatif sur la capacité du NKS à produire des kystes. Cela suggère que P. sojae pourrait influencer le développement du NKS. La présence du nématode, quant à elle, n’a pas influencé l’efficacité de la résistance qualitative à gènes Rps contre P. sojae. En conséquence, les cultivars résistants aux deux agents pathogènes représentent une bonne option pour prévenir et lutter contre ces affections. / The soybean cyst nematode (SCN), Heterodera glycines, is the leading cause of economic losses in soybean in the United States. In Canada, it has been found in Ontario in 1988 and continues to spread every year. It was identified for the first time in Quebec in 2013 and soybean growers have already begun to deploy management tools. The most commonly used control method against SCN is the use of quantitative resistance genes and crop rotation. However, the most damaging organism in soybean in Quebec currently is Phytophthora root rot, caused by Phytophthora sojae. This root disease can also be controlled by genetically resistant cultivars (qualitative resistance with Rps genes). Because SCN is now present in regions struggling with P. sojae, it is important to determine if the cultivars will express sufficient resistance against these two major pathogens. In this context, the main objective of this project was to evaluate the interaction between these two organisms on soybean, according to the resistance (qualitative Rps genes/ or quantitative resistance to SCN) of the cultivars used. This study, in a hydroponic system, demonstrated that P. sojae has a negative impact on SCN capacity to produce cysts produced. This suggests that P. sojae might influence SCN development. On the other hand, resistant cultivars were not affected by the presence of both pathogens and the presence of the nematode did not influence the efficacy of qualitative Rps resistance gene against P. sojae. As a result, cultivars resistant to both pathogens are a good option for preventing and controlling these diseases.

<p>  </p> <p>Plant-parasitic nematodes are amongst the most important pathogens impacting crops. Potatoes and soybean are vital crops for rural livelihoods and essential for food security, but their cyst nematode parasites remain a significant constraint globally. <em>Globodera</em> and <em>Heterodera </em>species are amongst the most damaging and internationally recognized quarantine pests of these crops, causing up to 80% yield loss. Their second stage juveniles (J2s) penetrate the host plant root tips and establish a residence close to the vascular bundle from where they extract nutrients as they complete their life cycle. Restrictions of control chemicals have led to an urgent need for alternative control strategies for cyst nematodes. Biological control is a promising alternative control measure, and fungi possess many characteristics that could make them great biological control agents of cyst nematodes. Most nematode populations are thought to be regulated by their natural enemy community. It is unclear which fungi are best adapted as natural enemies of these parasites and how they might do this. This project aimed to (a) characterize and compare the mycobiome diversity of cyst nematode species; (b) isolate and characterize fungi associated with potato and soybean cyst nematodes (c) screen isolated fungi for their efficacy as biocontrol agents against cyst nematodes; and (d) describe any isolated fungi identified as new and having potential for cyst nematode antagonism. Cyst populations were collected from different regions and screened for fungi using culture-based methods. For our next-generation sequence data analysis, we found differences in fungal community assemblages between center of origin of the potato cyst nematode (Peru; South America) and the regions where these nematodes were introduced such as Europe and North America.  There was no significant difference in fungal community assemblages of cysts collected between the years 2019 and 2020. We characterized fungi associated with the cyst nematodes and found that the most frequently isolated genera were <em>Fusarium, Penicillium, Cylindrocarpon, Phoma, Aspergillus </em>and<em> Verticillium</em>. Filtrates from <em>Trichoderma</em> sp. 2, <em>Alternaria alternata, </em>and <em>Fusarium acaciae-mearnsii </em>were toxic on SCN eggs while <em>Purpureucillium lilacinum, Fusarium proliferatum</em> and <em>Aureobasidium</em> <em>ellingtonae </em>sp. nov. were toxic on PCN eggs and juveniles. A new species of <em>Aureobasidium</em> isolated from the potato cyst nematode (<em>Globodera ellingtonae</em>) for the first time, and having biocontrol potentials against this nematode, was also identified, and described. </p>

Made available in DSpace on 2014-07-29T16:24:16Z (GMT). No. of bitstreams: 1 Dissertacao Kassia Aparecida Garcia Barbosa.pdf: 931610 bytes, checksum: 10046fdd236ad9643625e61fc8a6a851 (MD5) Previous issue date: 2010-11-29 / This study evaluated the effect of herbicides on the population density of H. glycines in soybean cultivars, (one resistant and three susceptible) in natural infestation conditions. Experiments were done in Campo Alegre de Goiás and Gameleira de Goiás, agricultural year 2006/07, using randomized blocks, with three repetitions. The treatments were arranged in a factorial design 4 x 4 + 1, with four cultivars (BRSGO Ipameri, BRSGO Luziânia, BRSGO Jataí BRS Silvânia RR), four forms of weed control (hand weeding, chlorimuron-ethyl + lactofen, chlorimuron-ethyl and haloxyfop-methyl), and additional treatment represented by the combination of transgenic cultivar BRS Silvânia RR and herbicide glyphosate. In agricultural year 2009/2010, another test was conducted in Gameleira de Goiás, with four repetitions, in a factorial design 2 x 4 + 2, involving two cultivars (BRSGO Chapadões and BRSGO 8360), four forms of weed control (hand weeding, lactofen, chlorimuron-ethyl; haloxifop-r), and two additional treatments represented by the combination of transgenic cultivar BRS Valiosa RR with control manual weed and chemical control via herbicide glyphosate. In the agricultural year 2006/07, in Campo Alegre de Goiás, eighty days after planting, there was less formation of viable cysts in cultivar BRS Silvânia RR associated with the application of clorimuron + lactofen, compared to manual control. In Gameleira de Goias, it was found, forty days after planting, increase in the number of viable cysts using herbicides, compared with manual control, in cultivar susceptible BRSGO Luziânia, BRSGO Ipameri, resistant to H. glycines, the number of viable cysts was lower when applied herbicides clorimuron+lactofen or haloxyfop, compared the application of clorimuron. The herbicides had no effect on the number of females in susceptible and resistant cultivars in the year 2009/10. In cultivar susceptible BRSGO 8360, the herbicide haloxifop led to a smaller number of females, in comparison with clorimuron, 45 days after sowing. The herbicide lactofen, in the cultivar BRSGO Chapadões (resistant) was associated with increase in the number of viable cysts 45 days after sowing. This herbicide affects negatively the biomass of leaves, fresh green beans and dry bean in the cultivars BRSGO Chapadões and BRSGO 8360. / O trabalho objetivou avaliar o efeito de herbicidas sobre a densidade populacional de H. glycines em cultivares de soja (uma resistente e três suscetíveis), em condições naturais de infestação. Experimentos foram conduzidos em Campo Alegre de Goiás e Gameleira de Goiás, safra 2006/07, utilizando delineamento de blocos casualizados, com três repetições. Os tratamentos foram arranjados em esquema fatorial 4x4+1, sendo: quatro cultivares (BRSGO Ipameri, BRSGO Luziânia, BRSGO Jataí, BRS Silvânia RR); quatro formas de controle de plantas daninhas (arranquio manual, chlorimuron-etil+lactofen, chlorimuron-etil e haloxyfop-metil); e o tratamento adicional representado pela combinação da cultivar transgênica BRS Silvânia RR e o herbicida glifosato. Na safra 2009/10, outro ensaio foi conduzido em Gameleira de Goiás, com quatro repetições, em esquema fatorial 2x4+2, envolvendo duas cultivares (BRSGO Chapadões e BRSGO 8360) quatro formas de controle de plantas daninhas (arranquio manual, lactofen, chlorimuron-etil e haloxifop-r), e os dois tratamentos adicionais que consistiram das combinações entre a cultivar BRS Valiosa RR com o controle manual das plantas daninhas e com o controle químico via herbicida glifosato. Na safra 2006/07, em Campo Alegre de Goiás, aos oitenta dias após o plantio, observou-se menor formação de cistos viáveis na cultivar BRS Silvânia RR, associado à aplicação de clorimuron + lactofen, em comparação ao controle manual. Em Gameleira de Goiás, verificou-se, aos quarenta dias após o plantio, aumento do número de cistos viáveis com o uso de herbicidas, em comparação com o controle manual, na cultivar suscetível BRSGO Luziânia, já na cultivar BRSGO Ipameri, resistente a H. glycines, o número de cistos viáveis foi menor quando se aplicou os herbicidas clorimuron+lactofen ou haloxifop, em comparação à aplicação de clorimuron. Na safra 2009/10, os herbicidas não influenciaram o comportamento das cultivares (resistente ou suscetíveis) quanto ao número de fêmeas. Na cultivar suscetível BRSGO Luziânia, o herbicida haloxifop possibilitou a formação de menor número de fêmeas, em comparação com clorimuron, aos 45 dias após o plantio. O herbicida lactofen, em BRSGO Chapadões, resistente, esteve associado com o aumento na formação de cistos viáveis, aos 45 dias após o plantio. Este herbicida afetou negativamente a produção de biomassa de planta seca, vagem fresca e vagem seca nas cultivares BRSGO Chapadões e BRSGO 8360.